INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-08
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Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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respect to this document. Code Components extracted from this
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document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies.................................................34
3. Conventions used in this document.............................34
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer..................................45
4.2 GMA-based MX Convergence Sublayer.......................56
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer..........................67
4.4.1 Transmitter Procedures............................78
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message................................89
5.1 Keep-Alive Message.....................................910
5.2 Probe Message..........................................910
5.3 Packet Loss Report (PLR) Message......................1011
5.4 First Sequence Number (FSN) Message...................1112
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message................1314
5.7 Acknowledgement Message...............................1415
6 Security Considerations.....................................1415
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References................................1516
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management
Service draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet
Engineering Task Force (IETF), its areas, and its working
groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced, or obsoleted by
other documents at any time. It is inappropriate to use
Internet-Drafts as reference material or to cite them
other than as "work in progress."
The list of current Internet-Drafts can be accessed at
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accessed at http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified
as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's
Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the
date of publication of this document. Please review these
documents carefully, as they describe your rights and
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restrictions with respect to this document. Code
Components extracted from this document must include
Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to
multiple communication networks based on different
technology implementations and network architectures like
WiFi, LTE, and DSL. In such multi-connectivity scenario,
it is desirable to combine multiple access networks or
select the best one to improve quality of experience for a
user and improve overall network utilization and
efficiency. This document presents the u-plane protocols
for a multi access management services (MAMS) framework
that can be used to flexibly select the combination of
uplink and downlink access and core network paths having
the optimal performance, and user plane treatment for
improving network utilization and efficiency and enhanced
quality of experience for user applications.
Table of Contents
1. Introduction .......................................... 3
2. Terminologies ......................................... 3
3. Conventions used in this document ..................... 3
4 MAMS User-Plane Protocols ............................. 4
4.1 MX Adaptation Sublayer .......................... 5
4.2 GMA-based MX Convergence Sublayer ............... 6
4.3 MPTCP-based MX Convergence Sublayer ............. 7
4.4 GRE as MX Convergence Sublayer .................. 8
4.4.1 Transmitter Procedures .................... 8
4.4.2 Receiver Procedures ....................... 9
4.5 Co-existence of MX Adaptation and MX Convergence
Sublayers ............................................. 9
5. MX Convergence Control Message ....................... 10
5.1 Keep-Alive Message ............................. 11
5.2 Probe Message .................................. 11
5.3 Packet Loss Report (PLR) Message ............... 12
5.4 First Sequence Number (FSN) Message ............ 13
5.5 Coded MX SDU (CMS) Message ..................... 14
5.6 Traffic Splitting Update (TSU) Message ......... 16
5.7 Acknowledgement Message ........................ 17
6 Security Considerations .............................. 17
7 IANA Considerations .................................. 17
8 Contributing Authors ................................. 17
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9 References ........................................... 18
9.1 Normative References ........................... 18
9.2 Informative References ......................... 18
1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a
programmable framework to select and configure network
paths, as well as adapt to dynamic network conditions,
when multiple network connections can serve a client
device. It is based on principles of user plane
interworking that enables the solution to be deployed as
an overlay without impacting the underlying networks.
This document presents the u-plane protocols for enabling
the MAMS framework. It co-exists and complements the
existing protocols by providing a way to negotiate and
configure the protocols based on client and network
capabilities. Further it allows exchange of network state
information and leveraging network intelligence to
optimize the performance of such protocols. An important
goal for MAMS is to ensure that there is minimal or no
dependency on the actual access technology of the
participating links. This allows the scheme to be scalable
for addition of newer access technologies and for
independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-
MADP to the Application Server that corresponds to a
specific IP anchor that has assigned an IP address to the
client.
Delivery Connection: refers to the network path from the
N-MADP to the C-MADP.
"Network Connection Manager" (NCM), "Client Connection
Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in
this document are to be interpreted as described in
[MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
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and "OPTIONAL" in this document are to be interpreted as
described in [RFC2119].
The terminologies "Network Connection Manager" (NCM),
"Client Connection Manager" (CCM), "Network Multi Access
Data Proxy" (N-MADP), and "Client Multi Access Data Proxy"
(C-MADP) in this document are to be interpreted as
described in [MAMS].
4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified
in [MAMS].
+-----------------------------------------------
------+
| User Payload (e.g. IP PDU)
|
|-----------------------------------------------
------|
+--|-----------------------------------------------
------|--+
| |-----------------------------------------------
------| |
| | Multi-Access (MX) Convergence Sublayer
| |
| |-----------------------------------------------
------| |
| |-----------------------------------------------
------| |
| | MX Adaptation | MX Adaptation | MX Adaptation
| |
| | Sublayer | Sublayer | Sublayer
| |
| | (optional) | (optional) | (optional)
| |
| |-----------------------------------------------
------| |
| | Access #1 IP | Access #2 IP | Access #3 IP
| |
| +-----------------------------------------------
------+ |
+--------------------------------------------------
---------+
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Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs
multi-access specific tasks, e.g., access (path) selection,
multi-link (path) aggregation, splitting/reordering,
lossless switching, fragmentation, concatenation, keep-
alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs
functions to handle tunneling, network layer security, and
NAT.
The MX convergence sublayer operates on top of the MX
adaptation sublayer in the protocol stack. From the
Transmitter perspective, a User Payload (e.g. IP PDU) is
processed by the convergence sublayer first, and then by the
adaptation sublayer before being transported over a delivery
access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by
the MX adaptation sublayer first, and then by the MX
convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms
and protocols while transmitting user plane packets on the
network path:
o UDP Tunneling: The user plane packets of the anchor
connection can be encapsulated in a UDP tunnel of a
delivery connection between the N-MADP and C-MADP.
o IPsec Tunneling: The user plane packets of the anchor
connection are sent through an IPsec tunnel of a delivery
connection.
o Client Net Address Translation (NAT): The Client IP address
of user plane packet of the anchor connection is changed,
and sent over a delivery connection.
o Pass Through: The user plane packets are passing through
without any change over the anchor connection.
The MX adaptation sublayer also supports the following
mechanisms and protocols to ensure security of user plane
packets over the network path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established
between the N-MADP and C-MADP on the network path that is
considered untrusted.
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o DTLS: If UDP tunneling is used on the network path that is
considered "untrusted", DTLS (Datagram Transport Layer
Security) [RFC6347] can be used.
The Client NAT method is the most efficient due to no
tunneling overhead. It SHOULD be used if a delivery
connection is "trusted" and without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a
delivery connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on
trailer-based encapsulation [GMA]. Multiple access networks
are combined into a single IP connection. If NCM determines
that N-MADP is to be instantiated with GMA as the MX
Convergence Protocol, it exchanges the support of GMA
convergence capability in the discovery and capability
exchange procedures [MAMS].
+--------------------------------------------------
---+
| IP PDU
|
|--------------------------------------------------
---|
| GMA Convergence Sublayer
|
|--------------------------------------------------
---|
| MX Adaptation | MX Adaptation | MX Adaptation
|
| Sublayer | Sublayer | Sublayer
|
| (optional) | (optional) | (optional)
|
|--------------------------------------------------
---|
| Access #1 IP | Access #2 IP | Access #3 IP
|
+--------------------------------------------------
---+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX
Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU
(Protocol Data Unit) format [GMA]. If the MX adaptation
method is UDP tunneling and "MX header optimization" in the
"MX_UP_Setup_Configuration_Request" message [MAMS] is true,
the "IP length" and "IP checksum" header fields of the MX PDU
SHOULD remain unchanged. Otherwise, they should be updated
after adding or removing the GMA trailer in the convergence
sublayer.
+--------------------------------------------------
----+
| IP hdr | IP payload | GMA
Trailer | +---------------------
---------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on
MPTCP. Here, MPTCP is reused as the "MX Convergence Sublayer"
protocol. Multiple access networks are combined into a single
MPTCP connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX
Convergence Layer
If NCM determines that N-MADP is to be instantiated with
MPTCP as the MX Convergence Protocol, it exchanges the
support of MPTCP capability in the discovery and capability
exchange procedures [MAMS]. MPTCP proxy protocols
[MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
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4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE
(Generic Routing Encapsulation) [GRE2784]. Here, GRE is
reused as the "MX Convergence sub-layer" protocol. Multiple
access networks are combined into a single GRE connection.
Hence, no new u-plane protocol or PDU format is needed in
this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP)
|
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP
|
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX
Convergence Layer
If NCM determines that N-MADP is to be instantiated with GRE
as the MX Convergence Protocol, it exchanges the support of
GRE capability in the discovery and capability exchange
procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated
with GRE as the convergence protocol that transmits the GRE
packets. The Transmitter receives the User Payload (e.g. IP
PDU), encapsulates it with a GRE header and Delivery Protocol
(e.g. IP) header to generate the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header
information (e.g. IP address) can be created using the IP
header of the user payload or a virtual IP address. The
"Protocol Type" field of the delivery header is set to 47 (or
0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
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- If the transmitter is a C-MADP instance, then sets the
LSB 16 bits to the value of Connection ID for the Anchor
Connection associated with the user payload or sets to
0xFFFF if no Anchor Connection ID needs to be specified.
- All other fields in the GRE header including the
remaining bits in the key fields are set as per
[GRE_2784][GRE_2890].
4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with
GRE as the convergence protocol that receives the GRE
packets. The receiver processes the received packets per the
GRE procedures [GRE_2784, GRE_2890] and retrieves the GRE
header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF,
they are interpreted as the Connection ID of Anchor
Connection for the user payload. This is used to
identify the network path over which the User
Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the
remaining bits in the Key fields, are processed as per
[GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation
Layer (if present) before delivery over one of the network
paths.
4.5 Co-existence of MX Adaptation and MX Convergence
Sublayers
MAMS u-plane protocols support multiple combinations and
instances of user plane protocols to be used in the MX
Adaptation and the Convergence sublayers.
For example, one instance of the MX Convergence Layer can be
MPTCP Proxy [MPProxy][MPPlain] and another instance can be
Trailer-based. The MX Adaptation for each can be either UDP
tunnel or IPsec. IPsec may be set up for network paths
considered as untrusted by the operator, to protect the TCP
subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of
MX Convergence and MX Adaptation layer protocols, can coexist
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simultaneously and independently handle different traffic
types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP
to exchange control messages for keep-alive or path quality
estimation. The N-MADP end-point IP address and UDP port
number of the UDP connection is used to identify MX control
PDU. Figure 6 shows the MX control PDU format with the
following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor
and delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned
integer to identify the anchor connection
+ Delivery Connection ID (LSB 4 Bits): an unsigned
integer to identify the delivery connection
o MX Control Message (variable): the payload of the MX
control message
Figure 7 shows the MX convergence control protocol stack, and
MX control PDU goes through the MX adaptation sublayer the
same way as MX data PDU.
<----MX Control PDU Payload ---------
------>
+------------------------------------------------------------
------+
| IP header | UDP Header| Type | CID | MX Control
Message | +----------------------------
--------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP
|
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
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| Access #1 IP | Access #2 IP | Access #3 IP
|
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-
MADP may send out Keep-Alive message periodically over one or
multiple delivery connections, especially if UDP tunneling is
used as the adaptation method for the delivery connection
with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the
following fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence
number of the keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp
clock of the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
N-MADP may send out the Probe message for path quality
estimation. In response, C-MADP may send back the ACK
message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number
of the Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is
expected (1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe
message is sent during the initialization phase (0)
when the network path is not included for
transmission of user data or the active phase (1)
when the network path is included for transmission
of user data;
+ Bit #2: a bit flag to indicate the presence of the
Reverse Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the
delivery connection for sending out the ACK message on
the reverse path
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o Timestamp (4 Bytes): the current value of the timestamp
clock of the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2
of the "Probing Flag" field are set to "1". Moreover, Bit #2
of the "Probing Flag" field SHOULD be set to "0" if the Bit
#0 is "0", indicating the ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the
"Probing Flag" field is set to "1", the ACK message SHOULD be
sent over the same delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe
message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU
for example during handover. In response, C-MADP may
retransmit the lost MX SDU accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection which the ACK message is for;
o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class of the anchor connection
which the ACK message is for;
o ACK number (4 Bytes): the next (in-order) sequence
number (SN) that the sender of the PLR message is
expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst
(4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1
Byte)
C-MADP
N-MADP
|
|
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|<------------------ MX SDU (data packets)-----
---|
|
|
+---------------------------------+
|
|Packet Loss detected |
|
+---------------------------------+
|
|
|
|----- PLR Message ----------------------------
-->|
|<-------------retransmit(lost)MX SDUs --------
---|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an
example where the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest
MX SDU in its buffer if a lost MX SDU is not found in the
buffer after receiving the PLR message from C-MADP. In
response, C-MADP SHALL only report packet loss with SN not
smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class of the anchor connection
which the FSN message is for;
o First Sequence Number (4 Bytes): the sequence number
(SN) of the oldest MX SDU in the (retransmission) buffer
of the sender of the FSN message.
Figure 9 shows the MAMS retransmission procedure in an
example where the lost packet is not found.
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C-MADP
N-MADP
|
|
|<------------------ MX SDU (data packets)-----
---|
|
|
+---------------------------------+
|
|Packet Loss detected |
|
+---------------------------------+
|
|
|
|----- PLR Message ----------------------------
-->|
| +---------------
------+
| |Lost packet not
found|
| +---------------
------+
|<-------------FSN message --------------------
---|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support
downlink (or uplink) packet loss recovery through coding,
e.g. [CRLNC], [CTCP], [RLNC]. A coded MX SDU is generated by
applying a network coding algorithm to multiple consecutive
(uncoded) MX SDUs, and it is used for fast recovery without
retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection of the coded MX SDU;
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o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the
first (uncoded) MX SDU used to generate the coded MX
SDU.
o Fragmentation Control (FC) (1 Byte): to provide
necessary information for re-assembly, only needed if
the coded MX SDU is too long to transport in a single MX
control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to
generate the coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded)
MX SDU
+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded
MX SDU from N consecutive uncoded MX SDUs, and the a(i)
fields are not included in the message.
If the coded MX SDU is too long, it can be fragmented, and
transported by multiple MX control PDUs. The N, K, and a(i)
fields are only included in the MX PDU carrying the first
fragment of the coded MX SDU.
C-MADP
N-MADP
|
|
|<------------------ MX SDU #1 ----------------
---|
| lost<-------- MX SDU #2 ----------------
---|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)---
---|
+----------------------+
|
| MX SDU #2 recovered |
|
+----------------------+
|
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|
|
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or
uplink) traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection;
o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class;
o Sequence Number (2 Bytes): an unsigned integer to
identify the TSU message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the
traffic splitting configuration is for the reverse
path (1) or not (0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-
reversal is used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1)
Bytes):
+ StartSN (4 Bytes): the sequence number of the first
MX SDU using the traffic splitting configuration
provided by the TSU message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th
delivery connection, where connections are ordered
according to their Connection ID.
Let's use f(x) to denote the traffic splitting function,
which maps a MX SDU Sequence Number "x" to the i-th delivery
connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
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N is the total number of connections for delivering a data
flow, identified by (anchor) Connection ID and Traffic Class
ID.
When the bit-reversal bit is set to 1, the burst size L MUST
be a power of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) <
K[i]
Wherein F(.) is the bit reversal function [BITR] of the input
variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in
response to the successful reception of a PLR, FSN, or TSU
message.
C-MADP SHOULD send out the ACK message in response to a Probe
message with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of
the received message.
o Timestamp (4 Bytes): the current value of the timestamp
clock of the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the
underlying network transport paths. When this cannot be
assumed, NCM configures use of appropriate protocols for
security, e.g. IPsec [RFC4301] [RFC3948], DTLS [RFC6347].
7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
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9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119,
March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for
the Internet Protocol", RFC 4301,
DOI10.17487/RFC4301, December 2005,
<http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram
Transport Layer Security Version 1.2", RFC 6347,
January 2012, <http://www.rfc-
editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P.,
and T. Kivinen, "Internet Key Exchange Protocol
Version 2 (IKEv2)", STD 79, RFC 7296, DOI
10.17487/RFC7296, October 2014, <http://www.rfc-
editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro,
L., and M. Stenberg, "UDP Encapsulation of IPsec
ESP Packets", RFC 3948, DOI 10.17487/RFC3948,
January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy
mechanisms", https://tools.ietf.org/html/draft-
wei-mptcp-proxy-mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for
Network-Assisted MPTCP",
https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu,
"Multiple Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-
intarea-mams-protocol-03
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[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for
Generic Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-
gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing
Encapsulation (GRE)", RFC 2784 March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions
to GRE", RFC 2890 September 2000,
<http://www.rfc-editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial
Radio Access (E-UTRA); LTE-WLAN Radio Level
Integration Using Ipsec Tunnel (LWIP)
encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al.
Caterpillar RLNC (CRLNC): A Practical Finite
Sliding Window RLNC Approach, IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding
(RLNC)-Based Symbol Representation,
https://www.ietf.org/id/draft-heide-nwcrg-rlnc-
00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM
Review, 38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
SungHoon Seo
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Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management
Service draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet
Engineering Task Force (IETF), its areas, and its working
groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced, or obsoleted by
other documents at any time. It is inappropriate to use
Internet-Drafts as reference material or to cite them
other than as "work in progress."
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accessed at http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified
as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's
Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the
date of publication of this document. Please review these
documents carefully, as they describe your rights and
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restrictions with respect to this document. Code
Components extracted from this document must include
Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to
multiple communication networks based on different
technology implementations and network architectures like
WiFi, LTE, and DSL. In such multi-connectivity scenario,
it is desirable to combine multiple access networks or
select the best one to improve quality of experience for a
user and improve overall network utilization and
efficiency. This document presents the u-plane protocols
for a multi access management services (MAMS) framework
that can be used to flexibly select the combination of
uplink and downlink access and core network paths having
the optimal performance, and user plane treatment for
improving network utilization and efficiency and enhanced
quality of experience for user applications.
Table of Contents
1. Introduction .......................................... 3
2. Terminologies ......................................... 3
3. Conventions used in this document ..................... 3
4 MAMS User-Plane Protocols ............................. 4
4.1 MX Adaptation Sublayer .......................... 5
4.2 GMA-based MX Convergence Sublayer ............... 6
4.3 MPTCP-based MX Convergence Sublayer ............. 7
4.4 GRE as MX Convergence Sublayer .................. 8
4.4.1 Transmitter Procedures .................... 8
4.4.2 Receiver Procedures ....................... 9
4.5 Co-existence of MX Adaptation and MX Convergence
Sublayers ............................................. 9
5. MX Convergence Control Message ....................... 10
5.1 Keep-Alive Message ............................. 11
5.2 Probe Message .................................. 11
5.3 Packet Loss Report (PLR) Message ............... 12
5.4 First Sequence Number (FSN) Message ............ 13
5.5 Coded MX SDU (CMS) Message ..................... 14
5.6 Traffic Splitting Update (TSU) Message ......... 16
5.7 Acknowledgement Message ........................ 17
6 Security Considerations .............................. 17
7 IANA Considerations .................................. 17
8 Contributing Authors ................................. 17
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9 References ........................................... 18
9.1 Normative References ........................... 18
9.2 Informative References ......................... 18
1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a
programmable framework to select and configure network
paths, as well as adapt to dynamic network conditions,
when multiple network connections can serve a client
device. It is based on principles of user plane
interworking that enables the solution to be deployed as
an overlay without impacting the underlying networks.
This document presents the u-plane protocols for enabling
the MAMS framework. It co-exists and complements the
existing protocols by providing a way to negotiate and
configure the protocols based on client and network
capabilities. Further it allows exchange of network state
information and leveraging network intelligence to
optimize the performance of such protocols. An important
goal for MAMS is to ensure that there is minimal or no
dependency on the actual access technology of the
participating links. This allows the scheme to be scalable
for addition of newer access technologies and for
independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-
MADP to the Application Server that corresponds to a
specific IP anchor that has assigned an IP address to the
client.
Delivery Connection: refers to the network path from the
N-MADP to the C-MADP.
"Network Connection Manager" (NCM), "Client Connection
Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in
this document are to be interpreted as described in
[MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
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and "OPTIONAL" in this document are to be interpreted as
described in [RFC2119].
The terminologies "Network Connection Manager" (NCM),
"Client Connection Manager" (CCM), "Network Multi Access
Data Proxy" (N-MADP), and "Client Multi Access Data Proxy"
(C-MADP) in this document are to be interpreted as
described in [MAMS].
4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified
in [MAMS].
+-----------------------------------------------
------+
| User Payload (e.g. IP PDU)
|
|-----------------------------------------------
------|
+--|-----------------------------------------------
------|--+
| |-----------------------------------------------
------| |
| | Multi-Access (MX) Convergence Sublayer
| |
| |-----------------------------------------------
------| |
| |-----------------------------------------------
------| |
| | MX Adaptation | MX Adaptation | MX Adaptation
| |
| | Sublayer | Sublayer | Sublayer
| |
| | (optional) | (optional) | (optional)
| |
| |-----------------------------------------------
------| |
| | Access #1 IP | Access #2 IP | Access #3 IP
| |
| +-----------------------------------------------
------+ |
+--------------------------------------------------
---------+
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Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs
multi-access specific tasks, e.g., access (path) selection,
multi-link (path) aggregation, splitting/reordering,
lossless switching, fragmentation, concatenation, keep-
alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs
functions to handle tunneling, network layer security, and
NAT.
The MX convergence sublayer operates on top of the MX
adaptation sublayer in the protocol stack. From the
Transmitter perspective, a User Payload (e.g. IP PDU) is
processed by the convergence sublayer first, and then by the
adaptation sublayer before being transported over a delivery
access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by
the MX adaptation sublayer first, and then by the MX
convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms
and protocols while transmitting user plane packets on the
network path:
o UDP Tunneling: The user plane packets of the anchor
connection can be encapsulated in a UDP tunnel of a
delivery connection between the N-MADP and C-MADP.
o IPsec Tunneling: The user plane packets of the anchor
connection are sent through an IPsec tunnel of a delivery
connection.
o Client Net Address Translation (NAT): The Client IP address
of user plane packet of the anchor connection is changed,
and sent over a delivery connection.
o Pass Through: The user plane packets are passing through
without any change over the anchor connection.
The MX adaptation sublayer also supports the following
mechanisms and protocols to ensure security of user plane
packets over the network path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established
between the N-MADP and C-MADP on the network path that is
considered untrusted.
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o DTLS: If UDP tunneling is used on the network path that is
considered "untrusted", DTLS (Datagram Transport Layer
Security) [RFC6347] can be used.
The Client NAT method is the most efficient due to no
tunneling overhead. It SHOULD be used if a delivery
connection is "trusted" and without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a
delivery connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on
trailer-based encapsulation [GMA]. Multiple access networks
are combined into a single IP connection. If NCM determines
that N-MADP is to be instantiated with GMA as the MX
Convergence Protocol, it exchanges the support of GMA
convergence capability in the discovery and capability
exchange procedures [MAMS].
+--------------------------------------------------
---+
| IP PDU
|
|--------------------------------------------------
---|
| GMA Convergence Sublayer
|
|--------------------------------------------------
---|
| MX Adaptation | MX Adaptation | MX Adaptation
|
| Sublayer | Sublayer | Sublayer
|
| (optional) | (optional) | (optional)
|
|--------------------------------------------------
---|
| Access #1 IP | Access #2 IP | Access #3 IP
|
+--------------------------------------------------
---+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX
Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU
(Protocol Data Unit) format [GMA]. If the MX adaptation
method is UDP tunneling and "MX header optimization" in the
"MX_UP_Setup_Configuration_Request" message [MAMS] is true,
the "IP length" and "IP checksum" header fields of the MX PDU
SHOULD remain unchanged. Otherwise, they should be updated
after adding or removing the GMA trailer in the convergence
sublayer.
+--------------------------------------------------
----+
| IP hdr | IP payload | GMA
Trailer | +---------------------
---------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on
MPTCP. Here, MPTCP is reused as the "MX Convergence Sublayer"
protocol. Multiple access networks are combined into a single
MPTCP connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX
Convergence Layer
If NCM determines that N-MADP is to be instantiated with
MPTCP as the MX Convergence Protocol, it exchanges the
support of MPTCP capability in the discovery and capability
exchange procedures [MAMS]. MPTCP proxy protocols
[MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
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4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE
(Generic Routing Encapsulation) [GRE2784]. Here, GRE is
reused as the "MX Convergence sub-layer" protocol. Multiple
access networks are combined into a single GRE connection.
Hence, no new u-plane protocol or PDU format is needed in
this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP)
|
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP
|
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX
Convergence Layer
If NCM determines that N-MADP is to be instantiated with GRE
as the MX Convergence Protocol, it exchanges the support of
GRE capability in the discovery and capability exchange
procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated
with GRE as the convergence protocol that transmits the GRE
packets. The Transmitter receives the User Payload (e.g. IP
PDU), encapsulates it with a GRE header and Delivery Protocol
(e.g. IP) header to generate the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header
information (e.g. IP address) can be created using the IP
header of the user payload or a virtual IP address. The
"Protocol Type" field of the delivery header is set to 47 (or
0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
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- If the transmitter is a C-MADP instance, then sets the
LSB 16 bits to the value of Connection ID for the Anchor
Connection associated with the user payload or sets to
0xFFFF if no Anchor Connection ID needs to be specified.
- All other fields in the GRE header including the
remaining bits in the key fields are set as per
[GRE_2784][GRE_2890].
4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with
GRE as the convergence protocol that receives the GRE
packets. The receiver processes the received packets per the
GRE procedures [GRE_2784, GRE_2890] and retrieves the GRE
header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF,
they are interpreted as the Connection ID of Anchor
Connection for the user payload. This is used to
identify the network path over which the User
Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the
remaining bits in the Key fields, are processed as per
[GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation
Layer (if present) before delivery over one of the network
paths.
4.5 Co-existence of MX Adaptation and MX Convergence
Sublayers
MAMS u-plane protocols support multiple combinations and
instances of user plane protocols to be used in the MX
Adaptation and the Convergence sublayers.
For example, one instance of the MX Convergence Layer can be
MPTCP Proxy [MPProxy][MPPlain] and another instance can be
Trailer-based. The MX Adaptation for each can be either UDP
tunnel or IPsec. IPsec may be set up for network paths
considered as untrusted by the operator, to protect the TCP
subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of
MX Convergence and MX Adaptation layer protocols, can coexist
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simultaneously and independently handle different traffic
types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP
to exchange control messages for keep-alive or path quality
estimation. The N-MADP end-point IP address and UDP port
number of the UDP connection is used to identify MX control
PDU. Figure 6 shows the MX control PDU format with the
following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor
and delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned
integer to identify the anchor connection
+ Delivery Connection ID (LSB 4 Bits): an unsigned
integer to identify the delivery connection
o MX Control Message (variable): the payload of the MX
control message
Figure 7 shows the MX convergence control protocol stack, and
MX control PDU goes through the MX adaptation sublayer the
same way as MX data PDU.
<----MX Control PDU Payload ---------
------>
+------------------------------------------------------------
------+
| IP header | UDP Header| Type | CID | MX Control
Message | +----------------------------
--------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP
|
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
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| Access #1 IP | Access #2 IP | Access #3 IP
|
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-
MADP may send out Keep-Alive message periodically over one or
multiple delivery connections, especially if UDP tunneling is
used as the adaptation method for the delivery connection
with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the
following fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence
number of the keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp
clock of the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
N-MADP may send out the Probe message for path quality
estimation. In response, C-MADP may send back the ACK
message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number
of the Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is
expected (1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe
message is sent during the initialization phase (0)
when the network path is not included for
transmission of user data or the active phase (1)
when the network path is included for transmission
of user data;
+ Bit #2: a bit flag to indicate the presence of the
Reverse Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the
delivery connection for sending out the ACK message on
the reverse path
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o Timestamp (4 Bytes): the current value of the timestamp
clock of the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2
of the "Probing Flag" field are set to "1". Moreover, Bit #2
of the "Probing Flag" field SHOULD be set to "0" if the Bit
#0 is "0", indicating the ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the
"Probing Flag" field is set to "1", the ACK message SHOULD be
sent over the same delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe
message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU
for example during handover. In response, C-MADP may
retransmit the lost MX SDU accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection which the ACK message is for;
o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class of the anchor connection
which the ACK message is for;
o ACK number (4 Bytes): the next (in-order) sequence
number (SN) that the sender of the PLR message is
expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst
(4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1
Byte)
C-MADP
N-MADP
|
|
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|<------------------ MX SDU (data packets)-----
---|
|
|
+---------------------------------+
|
|Packet Loss detected |
|
+---------------------------------+
|
|
|
|----- PLR Message ----------------------------
-->|
|<-------------retransmit(lost)MX SDUs --------
---|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an
example where the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest
MX SDU in its buffer if a lost MX SDU is not found in the
buffer after receiving the PLR message from C-MADP. In
response, C-MADP SHALL only report packet loss with SN not
smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class of the anchor connection
which the FSN message is for;
o First Sequence Number (4 Bytes): the sequence number
(SN) of the oldest MX SDU in the (retransmission) buffer
of the sender of the FSN message.
Figure 9 shows the MAMS retransmission procedure in an
example where the lost packet is not found.
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C-MADP
N-MADP
|
|
|<------------------ MX SDU (data packets)-----
---|
|
|
+---------------------------------+
|
|Packet Loss detected |
|
+---------------------------------+
|
|
|
|----- PLR Message ----------------------------
-->|
| +---------------
------+
| |Lost packet not
found|
| +---------------
------+
|<-------------FSN message --------------------
---|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support
downlink (or uplink) packet loss recovery through coding,
e.g. [CRLNC], [CTCP], [RLNC]. A coded MX SDU is generated by
applying a network coding algorithm to multiple consecutive
(uncoded) MX SDUs, and it is used for fast recovery without
retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection of the coded MX SDU;
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o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the
first (uncoded) MX SDU used to generate the coded MX
SDU.
o Fragmentation Control (FC) (1 Byte): to provide
necessary information for re-assembly, only needed if
the coded MX SDU is too long to transport in a single MX
control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to
generate the coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded)
MX SDU
+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded
MX SDU from N consecutive uncoded MX SDUs, and the a(i)
fields are not included in the message.
If the coded MX SDU is too long, it can be fragmented, and
transported by multiple MX control PDUs. The N, K, and a(i)
fields are only included in the MX PDU carrying the first
fragment of the coded MX SDU.
C-MADP
N-MADP
|
|
|<------------------ MX SDU #1 ----------------
---|
| lost<-------- MX SDU #2 ----------------
---|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)---
---|
+----------------------+
|
| MX SDU #2 recovered |
|
+----------------------+
|
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|
|
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or
uplink) traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify
the anchor connection;
o Traffic Class ID (1 Byte): an unsigned integer to
identify the traffic class;
o Sequence Number (2 Bytes): an unsigned integer to
identify the TSU message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the
traffic splitting configuration is for the reverse
path (1) or not (0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-
reversal is used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1)
Bytes):
+ StartSN (4 Bytes): the sequence number of the first
MX SDU using the traffic splitting configuration
provided by the TSU message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th
delivery connection, where connections are ordered
according to their Connection ID.
Let's use f(x) to denote the traffic splitting function,
which maps a MX SDU Sequence Number "x" to the i-th delivery
connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
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N is the total number of connections for delivering a data
flow, identified by (anchor) Connection ID and Traffic Class
ID.
When the bit-reversal bit is set to 1, the burst size L MUST
be a power of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) <
K[i]
Wherein F(.) is the bit reversal function [BITR] of the input
variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in
response to the successful reception of a PLR, FSN, or TSU
message.
C-MADP SHOULD send out the ACK message in response to a Probe
message with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of
the received message.
o Timestamp (4 Bytes): the current value of the timestamp
clock of the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the
underlying network transport paths. When this cannot be
assumed, NCM configures use of appropriate protocols for
security, e.g. IPsec [RFC4301] [RFC3948], DTLS [RFC6347].
7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
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9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119,
March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for
the Internet Protocol", RFC 4301,
DOI10.17487/RFC4301, December 2005,
<http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram
Transport Layer Security Version 1.2", RFC 6347,
January 2012, <http://www.rfc-
editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P.,
and T. Kivinen, "Internet Key Exchange Protocol
Version 2 (IKEv2)", STD 79, RFC 7296, DOI
10.17487/RFC7296, October 2014, <http://www.rfc-
editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro,
L., and M. Stenberg, "UDP Encapsulation of IPsec
ESP Packets", RFC 3948, DOI 10.17487/RFC3948,
January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy
mechanisms", https://tools.ietf.org/html/draft-
wei-mptcp-proxy-mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for
Network-Assisted MPTCP",
https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu,
"Multiple Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-
intarea-mams-protocol-03
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[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for
Generic Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-
gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing
Encapsulation (GRE)", RFC 2784 March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions
to GRE", RFC 2890 September 2000,
<http://www.rfc-editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial
Radio Access (E-UTRA); LTE-WLAN Radio Level
Integration Using Ipsec Tunnel (LWIP)
encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al.
Caterpillar RLNC (CRLNC): A Practical Finite
Sliding Window RLNC Approach, IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding
(RLNC)-Based Symbol Representation,
https://www.ietf.org/id/draft-heide-nwcrg-rlnc-
00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM
Review, 38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
SungHoon Seo
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Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
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http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
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http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
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http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
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http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
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This Internet-Draft will expire on April 1,2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction...................................................3
2. Terminologies..................................................3
3. Conventions used in this document..............................3
4 MAMS User-Plane Protocols......................................4
4.1 MX Adaptation Sublayer...................................4
4.2 GMA-based MX Convergence Sublayer........................5
4.3 MPTCP-based MX Convergence Sublayer......................6
4.4 GRE as MX Convergence Sublayer...........................6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
8
5. MX Convergence Control Message.................................8
5.1 Keep-Alive Message.......................................9
5.2 Probe Message............................................9
5.3 Packet Loss Report (PLR) Message........................10
5.4 First Sequence Number (FSN) Message.....................11
5.5 Coded MX SDU (CMS) Message..............................12
5.6 Traffic Splitting Update (TSU) Message..................13
5.7 Acknowledgement Message.................................14
6 Security Considerations.......................................14
7 IANA Considerations...........................................15
8 Contributing Authors..........................................15
9 References....................................................15
9.1 Normative References....................................15
9.2 Informative References..................................15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
Zhu Expires April 1, 2020 [Page 17]
INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
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carefully, as they describe your rights and restrictions with
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document must include Simplified BSD License text as described in
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction..................................................... 3
2. Terminologies.................................................... 3
3. Conventions used in this document................................ 3
4 MAMS User-Plane Protocols........................................ 4
4.1 MX Adaptation Sublayer..................................... 4
4.2 GMA-based MX Convergence Sublayer.......................... 5
4.3 MPTCP-based MX Convergence Sublayer........................ 6
4.4 GRE as MX Convergence Sublayer............................. 6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers. 8
5. MX Convergence Control Message................................... 8
5.1 Keep-Alive Message......................................... 9
5.2 Probe Message.............................................. 9
5.3 Packet Loss Report (PLR) Message.......................... 10
5.4 First Sequence Number (FSN) Message....................... 11
5.5 Coded MX SDU (CMS) Message................................ 12
5.6 Traffic Splitting Update (TSU) Message.................... 13
5.7 Acknowledgement Message................................... 14
6 Security Considerations......................................... 14
7 IANA Considerations............................................. 15
8 Contributing Authors............................................ 15
9 References...................................................... 15
9.1 Normative References...................................... 15
9.2 Informative References.................................... 15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 Co-existence of MX Adaptation and MX Convergence Sublayers
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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INTAREA J. Zhu
Internet Draft Intel
Intended status: Standards Track S. Seo
Expires: April 1,2020 Korea Telecom
S. Kanugovi
Nokia
S. Peng
Huawei
October 1, 2019
User-Plane Protocols for Multiple Access Management Service
draft-zhu-intarea-mams-user-protocol-07
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
Today, a device can be simultaneously connected to multiple
communication networks based on different technology implementations
and network architectures like WiFi, LTE, and DSL. In such multi-
connectivity scenario, it is desirable to combine multiple access
networks or select the best one to improve quality of experience for
a user and improve overall network utilization and efficiency. This
document presents the u-plane protocols for a multi access
management services (MAMS) framework that can be used to flexibly
select the combination of uplink and downlink access and core
network paths having the optimal performance, and user plane
treatment for improving network utilization and efficiency and
enhanced quality of experience for user applications.
Table of Contents
1. Introduction................................................... 3
2. Terminologies.................................................. 3
3. Conventions used in this document.............................. 3
4 MAMS User-Plane Protocols...................................... 4
4.1 MX Adaptation Sublayer................................... 4
4.2 GMA-based MX Convergence Sublayer........................ 5
4.3 MPTCP-based MX Convergence Sublayer...................... 6
4.4 GRE as MX Convergence Sublayer........................... 6
4.4.1 Transmitter Procedures.............................7
4.4.2 Receiver Procedures................................8
4.5 MX Adaptation and Convergence Co-existence............... 8
5. MX Convergence Control Message................................. 8
5.1 Keep-Alive Message....................................... 9
5.2 Probe Message............................................ 9
5.3 Packet Loss Report (PLR) Message........................ 10
5.4 First Sequence Number (FSN) Message..................... 11
5.5 Coded MX SDU (CMS) Message.............................. 12
5.6 Traffic Splitting Update (TSU) Message.................. 13
5.7 Acknowledgement Message................................. 14
6 Security Considerations....................................... 14
7 IANA Considerations........................................... 15
8 Contributing Authors.......................................... 15
9 References.................................................... 15
9.1 Normative References.................................... 15
9.2 Informative References.................................. 15
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1. Introduction
Multi Access Management Service (MAMS) [MAMS] is a programmable
framework to select and configure network paths, as well as adapt to
dynamic network conditions, when multiple network connections can
serve a client device. It is based on principles of user plane
interworking that enables the solution to be deployed as an overlay
without impacting the underlying networks.
This document presents the u-plane protocols for enabling the MAMS
framework. It co-exists and complements the existing protocols by
providing a way to negotiate and configure the protocols based on
client and network capabilities. Further it allows exchange of
network state information and leveraging network intelligence to
optimize the performance of such protocols. An important goal for
MAMS is to ensure that there is minimal or no dependency on the
actual access technology of the participating links. This allows the
scheme to be scalable for addition of newer access technologies and
for independent evolution of the existing access technologies.
2. Terminologies
Anchor Connection: refers to the network path from the N-MADP to the
Application Server that corresponds to a specific IP anchor that has
assigned an IP address to the client.
Delivery Connection: refers to the network path from the N-MADP to
the C-MADP.
"Network Connection Manager" (NCM), "Client Connection Manager"
(CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi
Access Data Proxy" (C-MADP) in this document are to be interpreted
as described in [MAMS].
3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminologies "Network Connection Manager" (NCM), "Client
Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-
MADP), and "Client Multi Access Data Proxy" (C-MADP) in this
document are to be interpreted as described in [MAMS].
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4 MAMS User-Plane Protocols
Figure 1 shows the MAMS u-plane protocol stack as specified in [MAMS].
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
+--|-----------------------------------------------------|--+
| |-----------------------------------------------------| |
| | Multi-Access (MX) Convergence Sublayer | |
| |-----------------------------------------------------| |
| |-----------------------------------------------------| |
| | MX Adaptation | MX Adaptation | MX Adaptation | |
| | Sublayer | Sublayer | Sublayer | |
| | (optional) | (optional) | (optional) | |
| |-----------------------------------------------------| |
| | Access #1 IP | Access #2 IP | Access #3 IP | |
| +-----------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: MAMS U-plane Protocol Stack
It consists of the following two Sublayers:
o Multi-Access (MX) Convergence Sublayer: This layer performs multi-
access specific tasks, e.g., access (path) selection, multi-link
(path) aggregation, splitting/reordering, lossless switching,
fragmentation, concatenation, keep-alive, and probing etc.
o Multi-Access (MX) Adaptation Sublayer: This layer performs functions
to handle tunneling, network layer security, and NAT.
The MX convergence sublayer operates on top of the MX adaptation
sublayer in the protocol stack. From the Transmitter perspective, a
User Payload (e.g. IP PDU) is processed by the convergence sublayer
first, and then by the adaptation sublayer before being transported
over a delivery access connection; from the Receiver perspective, an IP
packet received over a delivery connection is processed by the MX
adaptation sublayer first, and then by the MX convergence sublayer.
4.1 MX Adaptation Sublayer
The MX adaptation sublayer supports the following mechanisms and
protocols while transmitting user plane packets on the network path:
o UDP Tunneling: The user plane packets of the anchor connection can be
encapsulated in a UDP tunnel of a delivery connection between the N-
MADP and C-MADP.
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o IPsec Tunneling: The user plane packets of the anchor connection are
sent through an IPsec tunnel of a delivery connection.
o Client Net Address Translation (NAT): The Client IP address of user
plane packet of the anchor connection is changed, and sent over a
delivery connection.
o Pass Through: The user plane packets are passing through without any
change over the anchor connection.
The MX adaptation sublayer also supports the following mechanisms and
protocols to ensure security of user plane packets over the network
path.
o IPsec Tunneling: An IPsec [RFC7296] tunnel is established between the
N-MADP and C-MADP on the network path that is considered untrusted.
o DTLS: If UDP tunneling is used on the network path that is considered
"untrusted", DTLS (Datagram Transport Layer Security) [RFC6347] can
be used.
The Client NAT method is the most efficient due to no tunneling
overhead. It SHOULD be used if a delivery connection is "trusted" and
without NAT function on the path.
The UDP or IPsec Tunnelling method SHOULD be used if a delivery
connection has a NAT function placed on the path.
4.2 GMA-based MX Convergence Sublayer
Figure 2 shows the MAMS u-plane protocol stack based on trailer-based
encapsulation [GMA]. Multiple access networks are combined into a
single IP connection. If NCM determines that N-MADP is to be
instantiated with GMA as the MX Convergence Protocol, it exchanges the
support of GMA convergence capability in the discovery and capability
exchange procedures [MAMS].
+-----------------------------------------------------+
| IP PDU |
|-----------------------------------------------------|
| GMA Convergence Sublayer |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 2: MAMS U-plane Protocol Stack with GMA as MX Convergence Layer
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Figure 3 shows the trailer-based Multi-Access (MX) PDU (Protocol Data
Unit) format [GMA]. If the MX adaptation method is UDP tunneling and
"MX header optimization" in the "MX_UP_Setup_Configuration_Request"
message [MAMS] is true, the "IP length" and "IP checksum" header fields
of the MX PDU SHOULD remain unchanged. Otherwise, they should be
updated after adding or removing the GMA trailer in the convergence
sublayer.
+------------------------------------------------------+
| IP hdr | IP payload | GMA Trailer |
+------------------------------------------------------+
Figure 3: GMA PDU Format
4.3 MPTCP-based MX Convergence Sublayer
Figure 4 shows the MAMS u-plane protocol stack based on MPTCP. Here,
MPTCP is reused as the "MX Convergence Sublayer" protocol. Multiple
access networks are combined into a single MPTCP connection. Hence, no
new u-plane protocol or PDU format is needed in this case.
|-----------------------------------------------------|
| MPTCP |
|-----------------------------------------------------|
| TCP | TCP | TCP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 4: MAMS U-plane Protocol Stack with MPTCP as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with MPTCP as the
MX Convergence Protocol, it exchanges the support of MPTCP capability
in the discovery and capability exchange procedures [MAMS]. MPTCP proxy
protocols [MPProxy][MPPlain] SHOULD be used to manage traffic steering
and aggregation over multiple delivery connections.
4.4 GRE as MX Convergence Sublayer
Figure 5 shows the MAMS u-plane protocol stack based on GRE (Generic
Routing Encapsulation) [GRE2784]. Here, GRE is reused as the "MX
Convergence sub-layer" protocol. Multiple access networks are combined
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into a single GRE connection. Hence, no new u-plane protocol or PDU
format is needed in this case.
+-----------------------------------------------------+
| User Payload (e.g. IP PDU) |
|-----------------------------------------------------|
| GRE as MX Convergence Sublayer |
|-----------------------------------------------------|
| GRE Delivery Protocol (e.g. IP) |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 5: MAMS U-plane Protocol Stack with GRE as MX Convergence
Layer
If NCM determines that N-MADP is to be instantiated with GRE as the MX
Convergence Protocol, it exchanges the support of GRE capability in the
discovery and capability exchange procedures [MAMS].
4.4.1 Transmitter Procedures
Transmitter is the N-MADP or C-MADP instance, instantiated with GRE as
the convergence protocol that transmits the GRE packets. The
Transmitter receives the User Payload (e.g. IP PDU), encapsulates it
with a GRE header and Delivery Protocol (e.g. IP) header to generate
the GRE Convergence PDU.
When IP is used as the GRE delivery protocol, the IP header information
(e.g. IP address) can be created using the IP header of the user
payload or a virtual IP address. The "Protocol Type" field of the
delivery header is set to 47 (or 0X2F, i.e. GRE)[IANA].
The GRE header fields are set as specified below,
- If the transmitter is a C-MADP instance, then sets the LSB 16 bits
to the value of Connection ID for the Anchor Connection associated
with the user payload or sets to 0xFFFF if no Anchor Connection ID
needs to be specified.
- All other fields in the GRE header including the remaining bits in
the key fields are set as per [GRE_2784][GRE_2890].
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4.4.2 Receiver Procedures
Receiver is the N-MADP or C-MADP instance, instantiated with GRE as the
convergence protocol that receives the GRE packets. The receiver
processes the received packets per the GRE procedures [GRE_2784,
GRE_2890] and retrieves the GRE header.
- If the Receiver is an N-MADP instance,
o Unless the LSB 16 Bits of the Key field are 0xFFFF, they are
interpreted as the Connection ID of Anchor Connection for the
user payload. This is used to identify the network path over
which the User Payload (GRE Payload) is to be transmitted.
- All other fields in the GRE header, including the remaining bits
in the Key fields, are processed as per [GRE_2784][GRE_2890].
The GRE Convergence PDU is passed onto the MX Adaptation Layer (if
present) before delivery over one of the network paths.
4.5 MX Adaptation and Convergence Co-existence
MAMS u-plane protocols support multiple combinations and instances of
user plane protocols to be used in the MX Adaptation and the
Convergence sublayers.
For example, one instance of the MX Convergence Layer can be MPTCP
Proxy [MPProxy][MPPlain] and another instance can be Trailer-based. The
MX Adaptation for each can be either UDP tunnel or IPsec. IPsec may be
set up for network paths considered as untrusted by the operator, to
protect the TCP subflow between client and MPTCP proxy traversing that
network path.
Each of the instances of MAMS user plane, i.e. combination of MX
Convergence and MX Adaptation layer protocols, can coexist
simultaneously and independently handle different traffic types.
5. MX Convergence Control Message
A UDP connection may be configured between C-MADP and N-MADP to
exchange control messages for keep-alive or path quality estimation.
The N-MADP end-point IP address and UDP port number of the UDP
connection is used to identify MX control PDU. Figure 6 shows the MX
control PDU format with the following fields:
o Type (1 Byte): the type of the MX control message
o CID (1 Byte): an unsigned integer to identify the anchor and
delivery connection of the MX control message
+ Anchor Connection ID (MSB 4 Bits): an unsigned integer to
identify the anchor connection
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+ Delivery Connection ID (LSB 4 Bits): an unsigned integer to
identify the delivery connection
o MX Control Message (variable): the payload of the MX control
message
Figure 7 shows the MX convergence control protocol stack, and MX
control PDU goes through the MX adaptation sublayer the same way as MX
data PDU.
<----MX Control PDU Payload --------------->
+------------------------------------------------------------------+
| IP header | UDP Header| Type | CID | MX Control Message |
+------------------------------------------------------------------+
Figure 6: MX Control PDU Format
|-----------------------------------------------------|
| MX Convergence Control Messages |
|-----------------------------------------------------|
| UDP/IP |
|-----------------------------------------------------|
| MX Adaptation | MX Adaptation | MX Adaptation |
| Sublayer | Sublayer | Sublayer |
| (optional) | (optional) | (optional) |
|-----------------------------------------------------|
| Access #1 IP | Access #2 IP | Access #3 IP |
+-----------------------------------------------------+
Figure 7: MX Convergence Control Protocol Stack
5.1 Keep-Alive Message
The "Type" field is set to "0" for Keep-Alive messages. C-MADP may send
out Keep-Alive message periodically over one or multiple delivery
connections, especially if UDP tunneling is used as the adaptation
method for the delivery connection with a NAT function on the path.
A Keep-Alive message is 6 Bytes long, and consists of the following
fields:
o Keep-Alive Sequence Number (2 Bytes): the sequence number of the
keep-alive message
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
5.2 Probe Message
The "Type" field is set to "1" for Probe messages.
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N-MADP may send out the Probe message for path quality estimation. In
response, C-MADP may send back the ACK message.
A Probe message consists of the following fields:
o Probing Sequence Number (2 Bytes): the sequence number of the
Probe REQ message
o Probing Flag (1 Byte):
+ Bit #0: a ACK flag to indicate if the ACK message is expected
(1) or not (0);
+ Bit #1: a Probe Type flag to indicate if the Probe message is
sent during the initialization phase (0) when the network
path is not included for transmission of user data or the
active phase (1) when the network path is included for
transmission of user data;
+ Bit #2: a bit flag to indicate the presence of the Reverse
Connection ID (R-CID) field.
+ Bit #3~7: reserved
o Reverse Connection ID (1 Byte): the connection ID of the delivery
connection for sending out the ACK message on the reverse path
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
o Padding (variable)
The "R-CID" field is only present if both Bit #0 and Bit #2 of the
"Probing Flag" field are set to "1". Moreover, Bit #2 of the "Probing
Flag" field SHOULD be set to "0" if the Bit #0 is "0", indicating the
ACK message is not expected.
If the "R-CID" field is not present but the Bit #0 of the "Probing
Flag" field is set to "1", the ACK message SHOULD be sent over the same
delivery connection as the Probe message.
The "Padding" field is used to control the length of Probe message.
5.3 Packet Loss Report (PLR) Message
The "Type" field is set to "2" for PLR messages.
C-MADP may send out the PLR messages to report lost MX SDU for example
during handover. In response, C-MADP may retransmit the lost MX SDU
accordingly.
A PLR message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the ACK message is for;
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o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the ACK message is
for;
o ACK number (4 Bytes): the next (in-order) sequence number (SN)
that the sender of the PLR message is expecting
o Number of Loss Bursts (1 Byte)
For each loss burst, include the following
+ Sequence Number of the first lost MX SDU in a burst (4 Bytes)
+ Number of consecutive lost MX SDUs in the burst (1 Byte)
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
|<-------------retransmit(lost)MX SDUs -----------|
Figure 8: MAMS Retransmission Procedure
Figure 8 shows the MAMS retransmission procedure in an example where
the lost packet is found and retransmitted.
5.4 First Sequence Number (FSN) Message
The "Type" field is set to "3" for FSN messages.
N-MADP may send out the FSN messages to indicate the oldest MX SDU in
its buffer if a lost MX SDU is not found in the buffer after receiving
the PLR message from C-MADP. In response, C-MADP SHALL only report
packet loss with SN not smaller than FSN.
A FSN message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection which the FSN message is for;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the anchor connection which the FSN message is
for;
o First Sequence Number (4 Bytes): the sequence number (SN) of the
oldest MX SDU in the (retransmission) buffer of the sender of the
FSN message.
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Figure 9 shows the MAMS retransmission procedure in an example where
the lost packet is not found.
C-MADP N-MADP
| |
|<------------------ MX SDU (data packets)--------|
| |
+---------------------------------+ |
|Packet Loss detected | |
+---------------------------------+ |
| |
|----- PLR Message ------------------------------>|
| +---------------------+
| |Lost packet not found|
| +---------------------+
|<-------------FSN message -----------------------|
Figure 9: MAMS Retransmission Procedure with FSN
5.5 Coded MX SDU (CMS) Message
The "Type" field is set to "4" for CMS messages.
N-MADP (or C-MADP) may send out the CMS message to support downlink (or
uplink) packet loss recovery through coding, e.g. [CRLNC], [CTCP],
[RLNC]. A coded MX SDU is generated by applying a network coding
algorithm to multiple consecutive (uncoded) MX SDUs, and it is used for
fast recovery without retransmission if any of the MX SDUs is lost.
A Coded MX SDU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection of the coded MX SDU;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class of the coded MX;
o Sequence Number (4 Bytes): the sequence number of the first
(uncoded) MX SDU used to generate the coded MX SDU.
o Fragmentation Control (FC) (1 Byte): to provide necessary
information for re-assembly, only needed if the coded MX SDU is
too long to transport in a single MX control PDU.
o N (1 Byte): the number of consecutive MX SDUs used to generate the
coded MX SDU
o K (1 Byte): the length (in terms of bits) of the coding
coefficient field
o Coding Coefficient ( N x K / 8 Bytes)
+ a(i): the coding coefficient of the i-th (uncoded) MX SDU
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+ padding
o Coded MX SDU (variable): the coded MX SDU
If K = 0, the simple XOR method is used to generate the Coded MX SDU
from N consecutive uncoded MX SDUs, and the a(i) fields are not
included in the message.
If the coded MX SDU is too long, it can be fragmented, and transported
by multiple MX control PDUs. The N, K, and a(i) fields are only
included in the MX PDU carrying the first fragment of the coded MX SDU.
C-MADP N-MADP
| |
|<------------------ MX SDU #1 -------------------|
| lost<-------- MX SDU #2 -------------------|
|<---- CMS Message (MX SDU #1 XOR MX SDU #2)------|
+----------------------+ |
| MX SDU #2 recovered | |
+----------------------+ |
| |
Figure 10: MAMS Packet Recovery Procedure with XOR Coding
5.6 Traffic Splitting Update (TSU) Message
The "Type" field is set to "5" for TSU messages.
N-MADP (or C-MADP) may send out a TSU message if downlink (or uplink)
traffic splitting configuration has changed.
A TSU message consists of the following fields:
o Connection ID (1 Byte): an unsigned integer to identify the anchor
connection;
o Traffic Class ID (1 Byte): an unsigned integer to identify the
traffic class;
o Sequence Number (2 Bytes): an unsigned integer to identify the TSU
message.
o Flags (1 Byte)
+ Bit #0: a Reverse Path bit flag to indicate if the traffic
splitting configuration is for the reverse path (1) or not
(0);
+ Bit #1: a Bit-Reversal bit flag to indicate if bit-reversal is
used in traffic splitting
+ Others: reserved.
o Traffic Splitting Configuration Parameters ( 5 + (N -1) Bytes):
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+ StartSN (4 Bytes): the sequence number of the first MX SDU
using the traffic splitting configuration provided by the TSU
message
+ L (1 Byte): the traffic splitting burst size
+ K(i): the traffic splitting threshold of the i-th delivery
connection, where connections are ordered according to their
Connection ID.
Let's use f(x) to denote the traffic splitting function, which maps a
MX SDU Sequence Number "x" to the i-th delivery connection.
f(x)=i, if K[i-1]< or = mod(x - StartSN, L) < K[i]
Wherein, 1 < or = i < N, K[0]=0, and K[N]=L.
N is the total number of connections for delivering a data flow,
identified by (anchor) Connection ID and Traffic Class ID.
When the bit-reversal bit is set to 1, the burst size L MUST be a power
of 2, and the traffic splitting function is
f(x)=i, if K[i-1]< or = F(mod(x - StartSN, L)) < K[i]
Wherein F(.) is the bit reversal function [BITR] of the input variable.
5.7 Acknowledgement Message
The "Type" field is set to "6" for ACK messages.
C-MADP (or N-MADP) SHOULD send out the ACK message in response to the
successful reception of a PLR, FSN, or TSU message.
C-MADP SHOULD send out the ACK message in response to a Probe message
with the ACK flag set to "1".
The ACK message consists of the following fields:
o Acknowledgment Number (2 Bytes): the sequence number of the
received message.
o Timestamp (4 Bytes): the current value of the timestamp clock of
the sender in the unit of 100 microseconds.
6 Security Considerations
User data in MAMS framework rely on the security of the underlying
network transport paths. When this cannot be assumed, NCM configures
use of appropriate protocols for security, e.g. IPsec [RFC4301]
[RFC3948], DTLS [RFC6347].
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7 IANA Considerations
This draft makes no requests of IANA.
8 Contributing Authors
The editors gratefully acknowledge the following additional
contributors in alphabetical order: Salil Agarwal/Nokia, Hema
Pentakota/Nokia.
9 References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
9.2 Informative References
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012,
<http://www.rfc-editor.org/info/rfc6347>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
3948, DOI 10.17487/RFC3948, January 2005, <http://www.rfc-
editor.org/info/rfc3948>.
[MPProxy] X. Wei, C. Xiong, and E. Lopez, "MPTCP proxy mechanisms",
https://tools.ietf.org/html/draft-wei-mptcp-proxy-
mechanism-02
[MPPlain] M. Boucadair et al, "An MPTCP Option for Network-Assisted
MPTCP", https://www.ietf.org/id/draft-boucadair-mptcp-
plain-mode-09.txt
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[MAMS] S. Kanugovi, S. Vasudevan, F. Baboescu, and J. Zhu, "Multiple
Access Management Protocol",
https://tools.ietf.org/html/draft-kanugovi-intarea-mams-
protocol-03
[GMA] J. Zhu, "Trailer-based Encapsulation Protocols for Generic
Multi-Access Convergence",
https://tools.ietf.org/html/draft-zhu-intarea-gma-01
[GRE2784] D. Farinacci, et al., "Generic Routing Encapsulation
(GRE)", RFC 2784 March 2000, <http://www.rfc-
editor.org/info/rfc2784>.
[GRE2890] G. Dommety, "Key and Sequence Number Extensions to GRE",
RFC 2890 September 2000, <http://www.rfc-
editor.org/info/rfc2890>.
[IANA] https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml
[LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio Access
(E-UTRA); LTE-WLAN Radio Level Integration Using Ipsec
Tunnel (LWIP) encapsulation; Protocol specification"
[RFC791] Internet Protocol, September 1981
[CRLNC] S Wunderlich, F Gabriel, S Pandi, et al. Caterpillar RLNC
(CRLNC): A Practical Finite Sliding Window RLNC Approach,
IEEE Access, 2017
[CTCP] M. Kim, et al. Network Coded TCP (CTCP), eprint
arXiv:1212.2291, 2012
[RLNC] J. Heide, et al. Random Linear Network Coding (RLNC)-Based
Symbol Representation, https://www.ietf.org/id/draft-
heide-nwcrg-rlnc-00.txt
[BITR] Alan H. Karp, "Bit reversal on uniprocessors", SIAM Review,
38 (1): 1-26, 1996.
Authors' Addresses
Jing Zhu
Intel
Email: jing.z.zhu@intel.com
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Internet-Draft MAMS u-plane protocols October 2019
SungHoon Seo
Korea Telecom
Email: sh.seo@kt.com
Satish Kanugovi
Nokia
Email: satish.k@nokia.com
Shuping Peng
Huawei
Email: pengshuping@huawei.com
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