MPLS Segment Routing in IP Networks
draft-bryant-mpls-unified-ip-sr-02
The information below is for an old version of the document.
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|---|---|---|---|
| Authors | Stewart Bryant , Adrian Farrel , John Drake , Jeff Tantsura | ||
| Last updated | 2017-10-29 (Latest revision 2017-08-29) | ||
| Replaced by | draft-xu-mpls-sr-over-ip | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-bryant-mpls-unified-ip-sr-02
MPLS Working Group S. Bryant, Ed.
Internet-Draft Huawei
Intended status: Standards Track A. Farrel, Ed.
Expires: March 2, 2018 J. Drake
Juniper Networks
J. Tantsura
Individual
August 29, 2017
MPLS Segment Routing in IP Networks
draft-bryant-mpls-unified-ip-sr-02
Abstract
Segment routing is a source routed forwarding method that allows
packets to be steered through a network on paths other than the
shortest path derived from the routing protocol. The approach uses
information encoded in the packet header to partially or completely
specify the route the packet takes through the network, and does not
make use of a signaling protocol to pre-install paths in the network.
Two different encapsulations have been defined to enable segment
routing in an MPLS network or in an IPv6 network. While
acknowledging that there is a strong need to support segment routing
in both environments, this document defines a mechanism to carry MPLS
segment routing packets encapsulated in UDP. The resulting approach
is applicable to both IPv4 and IPv6 networks without the need for any
changes to the IP or segment routing specifications.
This document makes no changes to the segment routing architecture
and builds on existing protocol mechanisms such as the encapsulation
of MPLS within UDP defined in RFC 7510.
No new procedures are introduced, but existing mechanisms are
combined to achieve the desired result.
Requirements Language
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].
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 March 2, 2018.
Copyright Notice
Copyright (c) 2017 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The MPLS-SR-over-UDP Encoding Stack . . . . . . . . . . . . . 4
3. The Segment Routing Instruction Stack . . . . . . . . . . . . 5
3.1. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. UDP/IP Encapsulation . . . . . . . . . . . . . . . . . . . . 6
5. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 6
5.1. Domain Ingress Nodes . . . . . . . . . . . . . . . . . . 7
5.2. Legacy Transit Nodes . . . . . . . . . . . . . . . . . . 8
5.3. On-Path Pass-Through SR Nodes . . . . . . . . . . . . . . 8
5.4. SR Transit Nodes . . . . . . . . . . . . . . . . . . . . 9
5.5. Penultimate SR Transit Nodes . . . . . . . . . . . . . . 9
5.6. Domain Egress Nodes . . . . . . . . . . . . . . . . . . . 10
6. Modes of Deployment . . . . . . . . . . . . . . . . . . . . . 11
6.1. Interconnection of SR Domains . . . . . . . . . . . . . . 11
6.2. SR Within an IP Network . . . . . . . . . . . . . . . . . 12
7. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 13
8. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
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11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
13.1. Normative References . . . . . . . . . . . . . . . . . . 15
13.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
Segment routing (SR) [I-D.ietf-spring-segment-routing] is a source
routed forwarding method that allows packets to be steered through a
network on paths other than the shortest path derived from the
routing protocol. SR also allows the packets to be steered through a
set of packet processing functions along that path. SR uses
information encoded in the packet header to partially or completely
specify the route the packet takes through the network and does not
make use of a signaling protocol to pre-install paths in the network.
The approach to segment routing in IPv6 networks is known as SRv6 and
is described in [I-D.ietf-6man-segment-routing-header]. The
mechanism described encodes the segment routing instruction list as
an ordered list of 128-bit IPv6 addresses that is carried in a new
IPv6 extension header: the Source Routing Header (SRH).
MPLS-SPRING [I-D.ietf-spring-segment-routing-mpls] (also known as
MPLS Segment Routing or MPLS-SR) encodes the route the packet takes
through the network and the instructions to be applied to the packet
as it transits the network by imposing a stack of MPLS label entries
on the packet.
This document describes a method for running SR in IPv4 or IPv6
networks by using an MPLS-SR label stack carried in UDP. No change
is made to the MPLS-SR encoding mechanism as described in
[I-D.ietf-spring-segment-routing-mpls] where a sequence of 32 bit
units, one for each instruction, called the Segment Routing
Instruction Stack (SRIS) is used. Each basic unit is encoded as an
MPLS label stack entry and the segment routing instructions (i.e.,
the Segment Identifiers, SIDs) are encoded in the 20 bit MPLS Label
fields.
In summary, the processing described in this document is a
combination of normal MPLS-over-UDP behavior as described in
[RFC7510], MPLS-SR lookup and label-pop behavior as described in
[I-D.ietf-spring-segment-routing-mpls], and normal IP forwarding. No
new procedures are introduced, but existing mechanisms are combined
to achieve the desired result.
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The method defined is a complementary way of running SR in an IP
network that can be used alongside or interchangeably with that
defined in [I-D.ietf-6man-segment-routing-header]. Implementers and
deployers should consider the benefits and drawbacks of each method
and select the approach most suited to their needs.
2. The MPLS-SR-over-UDP Encoding Stack
The MPLS-SR-over-UDP encoding stack is shown in Figure 1.
+---------------------+
| |
| IP Header |
| |
+---------------------+
| |
| UDP Header |
| |
+---------------------+
| |
| Segment Routing |
| Instruction Stack |
~ ~
~ ~
| |
+---------------------+
| |
| Payload |
~ ~
~ ~
| |
+---------------------+
Figure 1: Packet Encapsulation
The payload may be of any type that, with an appropriate convergence
layer, can be carried over a packet network. It is anticipated that
the most common packet types will be IPv4, IPv6, native MPLS, and
pseudowires [RFC3985].
Preceding the Payload is the Segment Routing Instruction Stack (SRIS)
that carries the sequence of instructions to be executed on the
packet as it traverses the network. This is the Segment Identifier
(SID) stack that is the ordered list of segments described in
[I-D.ietf-spring-segment-routing].
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Preceding the SRIS is a UDP header. The UDP header is included to:
o Introduce entropy to allow equal-cost multi-path load balancing
(ECMP) [RFC2992] in the IP layer [RFC7510].
o Provide a protocol multiplexing layer as an alternative to using a
new IP type/next header.
o Allow transit through firewalls and other middleboxes.
o Provide disaggregation.
Preceding the UDP header is the IP header which may be IPv4 or IPv6.
3. The Segment Routing Instruction Stack
The SRIS consists of a sequence of Segment Identifiers as described
in [I-D.ietf-spring-segment-routing] encoded as an MPLS label stack
as described in [I-D.ietf-spring-segment-routing-mpls].
The top SRIS entry is the next instruction to be executed. When the
node to which this instruction is directed has processed the
instruction it is removed (popped) from the SRIS, and the next
instruction processed.
Each instruction is encoded in a single Label Stack Entry (LSE) as
shown in Figure 2. The structure of the LSE is unchanged from
[RFC3032].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instruction | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Instruction: Label Value, 20 bits
TC: Traffic Class, 3 bits
S: Bottom of Stack, 1 bit
TTL: Time to Live, 8 bits
Figure 2: SRIS Label Stack Entry
As with [I-D.ietf-spring-segment-routing-mpls] a 32 bit LSE is used
to carry each SR instruction. The instruction itself is carried in
the 20 bit Label Value field. The TC field has the normal meaning as
defined in [RFC3032] and modified in [RFC5462]. The S bit has bottom
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of stack semantics defined in [RFC3032]. TTL is discussed in
Section 3.1.
3.1. TTL
The setting of the TTL is application specific, but the following
operational consideration should be born in mind. In SR the size of
the label stack may be increased within a single routing domain by
various operations such as the pushing of a binding SID. Furthermore
in SR packets are not necessarily constrained to travel on the
shortest path with that routing domain. Consideration therefore has
to be given to possibility of a forwarding loop. To mitigate against
this it is RECOMMENDED that the TTL is continuously decremented as
the packet passes through the SR network regardless of any other
changes to the network layer encapsulation.
Further discussion of the use of TTL during tunnelling can be found
in [RFC4023].
4. UDP/IP Encapsulation
The procedures defined in [RFC7510] are followed. RFC7510 specifies
the values to be used in the UDP Source Port, Destination Port, and
Checksum fields.
An administrative domain, or set of administrative domains that are
sufficiently well managed and monitored to be able to safely use IP
segment routing is likely to comply with the requirements called out
in [RFC7510] to permit operation with a zero checksum over IPv6.
However each operator needs to validate the decision on whether or
not to use a UDP checksum for themselves.
The [RFC7510] UDP header may be carried over IPv4 or over IPv6.
The IP source address is the address of the encapsulating device.
The IP destination address is implied by the instruction at the top
of the instruction stack.
If IPv4 is in use, fragmentation is not permitted.
5. Elements of Procedure
Not all of the nodes in an SR domain are "SR capable" meaning that
they can process MPLS-SR packets. Some nodes may be "legacy routers"
that cannot handle SR packets but can forward IP packets. An SR
capable node may advertise its capabilities using the IGP as
described in Section 7. There are six types of node in an SR domain:
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o Domain ingress nodes that receive packets and encapsulate them for
transmission across the domain. These packets may be any payload
protocol including native IP packets or packets that are already
MPLS encapsulated.
o Legacy transit nodes that are IP routers but that are not able to
perform segment routing.
o Transit nodes that are SR capable but that are not identified by a
SID in the SID stack.
o Transit nodes that are SR capable and need to perform SR routing.
o The penultimate SR capable node on the path that processes the
last SID on the stack on behalf of the domain egress node.
o The domain egress node that forwards the payload packet for
ultimate delivery.
The following sub-sections describe the processing behavior in each
case.
In summary, the processing is a combination of normal MPLS-over-UDP
behavior as described in [RFC7510], MPLS-SR lookup and label-pop
behavior as described in [I-D.ietf-spring-segment-routing-mpls], and
normal IP forwarding. No new procedures are introduced, but existing
mechanisms ae combined to achieve the desired result.
The descriptions in the following sections represent the functional
behavior. Optimizations on this behavior may be possible in
implementations.
5.1. Domain Ingress Nodes
Domain ingress nodes receive packets from outside the domain and
encapsulate them to be forwarded across the domain. Received packets
may already be MPLS-SR packets (in the case of connecting two MPLS-SR
networks across a native IP network), or may be IP or MPLS packets.
In the latter case, the packet is classified by the domain ingress
node and an MPLS-SR stack is imposed. In the former case the MPLS-SR
stack is already in the packet. The top entry in the stack is popped
from the stack and retained for use below.
The packet is then encapsulated in UDP with the destination port set
to 6635 to indicate "MPLS-UDP" or to 6636 to indicate "MPLS-UDP-
DTLS"as described in [RFC7510]. The source UDP port is set randomly
or to provide entropy as described in [RFC7510].
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The packet is then encapsulated in IP for transmission across the
network. The IP source address is set to the domain ingress node,
and the destination address is set to the address corresponding to
the label that was previously popped from the stack.
This corresponds to sending the packet out of a virtual interface
that corresponds to a virtual link between the ingress node and the
next hop SR node realized by a UDP tunnel.
The packet is then sent into the IP network and is routed according
to the local FIB and applying hashing to resolve any ECMP choices.
5.2. Legacy Transit Nodes
A legacy transit node is an IP router that has no SR capabilities.
When such a router receives an MPLS-SR-in-UDP packet it will carry
out normal TTL processing and if the packet is still live it will
forward it as it would any other UDP-in-IP packet. The packet will
be routed toward the destination indicated in the packet header using
the local FIB and applying hashing to resolve any ECMP choices.
If the packet is mistakenly addressed to the legacy router, the UDP
tunnel will be terminated and the packet will be discarded either
because the MPLS-in-UDP port is not supported or because the
uncovered top label has not been allocated. This is, however, a
misconnection and should not occur unless there is a routing error.
5.3. On-Path Pass-Through SR Nodes
Just because a node is SR capable and receives an MPLS-SR-in-UDP
packet does not mean that it performs SR processing on the packet.
Only routers identified by SIDs in the SR stack need to do such
processing.
Routers that are not addressed by the destination address in the IP
header simply treat the packet as a normal UDP-in-IP packet carrying
out normal TTL processing and if the packet is still live routing the
packet according to the local FIB and applying hashing to resolve any
ECMP choices.
This is important because it means that the SR stack can be kept
relatively small and the packet can be steered through the network
using shortest path first routing between selected SR nodes.
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5.4. SR Transit Nodes
An SR capable node that is addressed by the top most SID in the stack
when that is not the last SID in the stack (i.e., the S bit is not
set) is an SR transit node. When an SR transit node receives an
MPLS-SR-in-UDP packet that is addressed to it, it acts as follows:
o Perform TTL processing as normal for an IP packet.
o Determine that the packet is addressed to the local node.
o Find that the payload is UDP and that the destination port
indicates MPLS-in-UDP.
o Strip the IP and UDP headers.
o Pop the top label from the SID stack and retain it for use below.
o Encapsulate the packet in UDP with the destination port set to
6635 (or 6636 for DTLS) and the source port set for entropy. The
entropy value SHOULD be retained from the received UDP header or
MAY be freshly generated since this is a new UDP tunnel.
o Encapsulate the packet in IP with the IP source address set to
this transit router, and the destination address set to the
address corresponding to the next SID in the stack.
o Send the packet into the IP network routing the packet according
to the local FIB and applying hashing to resolve any ECMP choices.
5.5. Penultimate SR Transit Nodes
The penultimate SR transit node is an SR transit node as described in
Section 5.4 where the SID for the node is directly followed by the
final SID (i.e., that of domain egress node). When a penultimate SR
transit node receives an MPLS-SR-in-UDP packet that is addressed to
it, it acts according to whether penultimate hop popping (PHP) is
supported for the final SID. That information could be indicated
using the control plane as described in Section 7.
If PHP is allowed the penultimate SR transit node acts as follows:
o Perform TTL processing as normal for an IP packet.
o Determine that the packet is addressed to the local node.
o Find that the payload is UDP and that the destination port
indicates MPLS-in-UDP.
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o Strip the IP and UDP headers.
o Pop the top label from the SID stack and retain it for use below.
o Pop the next label from the SID stack.
o Encapsulate the packet in UDP with the destination port set to
6635 (or 6636 for DTLS) and the source port set for entropy. The
entropy value SHOULD be retained from the received UDP header or
MAY be freshly generated since this is a new UDP tunnel.
o Encapsulate the packet in IP with the IP source address set to
this transit router, and the destination address set to the domain
egress node IP address corresponding to the label that was
previously popped from the stack.
o Send the packet into the IP network routing the packet according
to the local FIB and applying hashing to resolve any ECMP choices.
If PHP is not supported, the penultimate SR transit node just acts as
a normal SR transit node just as described in Section 5.4. However,
the penultimate SR transit node may be required to replace the final
SID with an MPLS-SR label stack entry carrying an explicit null label
value (0 for IPv4 and 2 for IPv6) before forwarding the packet. This
requirement may also be indicated by the control plane as described
in Section 7.
5.6. Domain Egress Nodes
The domain egress acts as follows:
o Perform TTL processing as normal for an IP packet.
o Determine that the packet is addressed to the local node.
o Find that the payload is UDP and that the destination port
indicates MPLS-in-UDP.
o Strip the IP and UDP headers.
o Pop the outermost SID if present (i.e., if PHP was not performed
as described in Section 5.5.
o Pop the explicit null label if it is present in the label stack as
requested by the domain egress and communicated in the control
plane as described in Section 7.
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o Forward the payload packet according to its type and the local
routing/forwarding mechanisms.
6. Modes of Deployment
As previously noted, the procedures described in this document may be
used to connect islands of SR functionality across an IP backbone, or
can provide SR function within a native IP network. This section
briefly expounds upon those two deployment modes.
6.1. Interconnection of SR Domains
Figure 3 shows two SR domains interconnected by an IP network. The
procedures described in this document are deployed at border routers
R1 and R2 and packets are carried across the backbone network in a
UDP tunnel.
R1 acts as the domain ingress as described in Section 5.1. It takes
the MPLS-SR packet from the SR domain, pops the top label and uses it
to identify its peer border router R2. R1 then encapsulates the
packet in UDP in IP and sends it toward R2.
Routers within the IP network simply forward the packet using normal
IP routing.
R2 acts as a domain egress router as described in Section 5.6. It
receives a packet that is addressed to it, strips the IP and UDP
headers, and acts on the payload SR label stack to continue to route
the packet.
________________________
______ ( ) ______
( ) ( IP Network ) ( )
( ) ( ) ( )
( -------- -------- )
( | Border | SR-in-UDP Tunnel | Border | )
( SR | Router |========================| Router | SR )
( | R1 | | R2 | )
( -------- -------- )
( ) ( ) ( )
(______) ( ) (______)
(________________________)
Figure 3: SR in UDP to Tunnel Between SR Sites
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6.2. SR Within an IP Network
Figure 4 shows the procedures defined in this document to provide SR
function across an IP network.
R1 receives a native packet and classifies it, determining that it
should be sent on the SR path R2-R3-R4-R5. It imposes a label stack
accordingly and then acts as a domain ingress as described in
Section 5.1. It pops the label for R2, and encapsulates the packet
in UDP in IP, sets the IP source to R1 and the IP destination to R2,
and sends the packet into the IP network.
Routers Ra and Rb are transit routers that simply forward the packets
using normal IP forwarding. They may be legacy transit routers (see
Section 5.2) or on-path pass-through SR nodes (see Section 5.3).
R2 is an SR transit nodes as described in Section 5.4. It receives a
packet addressed to it, strips the IP and UDP headers, and processes
the SR label stack. It pops the top label and uses it to identify
the next SR hop which is R3. R2 then encapsulates the packet in UDP
in IP setting the IP source to R2 and the IP destination to R3.
Rc, Rd, and Re are transit routers and perform as Ra and Rb.
R3 is an SR transit node and performs as R2.
R4 is a penultimate SR transit node as described in Section 5.5. It
receives a packet addressed to it, strips the IP and UDP headers, and
processes the SR label stack. It pops the top label and uses it to
identify the next SR hop which is R5.
R5 is the domain egress as described in Section 5.6. It receives a
packet addressed to it, strips the IP and UDP headers.
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__________________________________
__( IP Network )__
__( )__
( -- -- -- )
-------- -- -- |R2| -- |R3| -- |R4| -- --------
| Ingress| |Ra| |Rb| | | |Rc| | | |Rd| | | |Re| | Egress |
--->| Router |===========| |======| |======| |======| Router |--->
| R1 | | | | | | | | | | | | | | | | | | R5 |
-------- -- -- | | -- | | -- | | -- --------
(__ -- -- -- __)
(__ __)
(__________________________________)
Figure 4: SR Within an IP Network
7. Control Plane
This document is concerned with forwarding plane issues, and a
description of applicable control plane mechanisms is out of scope.
This section is provided only as a collection of references. No
changes to the control plane mechanisms for MPLS-SR are needed or
proposed.
A routers that is able to support SR can advertise the fact in the
IGP as follows:
o In IS-IS, by using the SR-Capabilities TLV as defined in
[I-D.ietf-isis-segment-routing-extensions]
o In OSPF/OSPFv3 by using the Router Information LSA as defined in
[I-D.ietf-ospf-segment-routing-extensions] and
[I-D.ietf-ospf-ospfv3-segment-routing-extensions].
Nodes can advertise SIDs using the mechanisms defined in
[I-D.ietf-isis-segment-routing-extensions],
[I-D.ietf-ospf-segment-routing-extensions], or
[I-D.ietf-ospf-ospfv3-segment-routing-extensions].
Support for PHP can be indicated in a SID advertisement using flags
in the advertisements as follows:
o For IS-IS, the N (no-PHP) flag in the Prefix-SID sub-TLV indicates
whether PHP is not to be used.
o For OSPF/OSPFv3, the NP (no-PHP) flag in the Prefix SID Sub-TLV
indicates whether PHP is not to be used.
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The requirement to use an explicit null SID if PHP is not in use can
be indicated in SID advertisement using the Explicit-Null Flag
(E-Flag). If set, the penultimate SR transit node replaces the final
SID with a SID containing an Explicit-NULL value (0 for IPv4 and 2
for IPv6) before forwarding the packet.
The method of advertising the tunnel encapsulation capability of a
router using IS-IS or OSPF are specified in
[I-D.ietf-isis-encapsulation-cap] and
[I-D.ietf-ospf-encapsulation-cap] respectively. No changes to those
procedures are needed in support of this work.
8. OAM
OAM at the payload layer follows the normal OAM procedures for the
payload. To the payload the whole SR network looks like a tunnel.
OAM in the IP domain follows the normal IP procedures. This can only
be carried out between on the IP hops between pairs of SR nodes.
OAM between instruction processing entities i.e. at the SR layer uses
the procedures documented for MPLS.
9. Security Considerations
The security consideration of [I-D.ietf-spring-ipv6-use-cases] and
[RFC7510] apply. DTLS [RFC6347] SHOULD be used where security is
needed on an MPLS-SR-over-UDP segment.
It is difficult for an attacker to pass a raw MPLS encoded packet
into a network and operators have considerable experience at
excluding such packets at the network boundaries.
It is easy for an ingress node to detect any attempt to smuggle IP
packet into the network since it would see that the UDP destination
port was set to MPLS. SR packets not having a destination address
terminating in the network would be transparently carried and would
pose no security risk to the network under consideration.
10. IANA Considerations
This document makes no IANA requests.
11. Acknowledgements
This draft was partly inspired by
[I-D.xu-mpls-unified-source-routing-instruction], and we acknowledge
the following authors of version -02 of that draft: Robert Raszuk,
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Uma Chunduri, Luis M. Contreras, Luay Jalil, Hamid Assarpour, Gunter
Van De Velde, Jeff Tantsura, and Shaowen Ma.
Thanks to Joel Halpern, Bruno Decraene, Loa Andersson, Ron Bonica,
Eric Rosen, Robert Raszuk, Wim Henderickx, Jim Guichard, and Gunter
Van De Velde for their insightful comments on this draft.
12. Contributors
o Mach Chen, Huawei Technologies, mach.chen@huawei.com
13. References
13.1. Normative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-12 (work in progress), June 2017.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-10
(work in progress), June 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <https://www.rfc-editor.org/info/rfc5462>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
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[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015, <https://www.rfc-
editor.org/info/rfc7510>.
13.2. Informative References
[I-D.ietf-6man-segment-routing-header]
Previdi, S., Filsfils, C., Raza, K., Leddy, J., Field, B.,
daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d.,
Matsushima, S., Leung, I., Linkova, J., Aries, E., Kosugi,
T., Vyncke, E., Lebrun, D., Steinberg, D., and R. Raszuk,
"IPv6 Segment Routing Header (SRH)", draft-ietf-6man-
segment-routing-header-07 (work in progress), July 2017.
[I-D.ietf-isis-encapsulation-cap]
Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
L., and L. Jalil, "Advertising Tunnelling Capability in
IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in
progress), April 2017.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and j. jefftant@gmail.com,
"IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-13 (work in progress), June
2017.
[I-D.ietf-ospf-encapsulation-cap]
Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L.
Jalil, "Advertising Tunneling Capability in OSPF", draft-
ietf-ospf-encapsulation-cap-06 (work in progress), July
2017.
[I-D.ietf-ospf-ospfv3-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
segment-routing-extensions-09 (work in progress), March
2017.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-19 (work in progress), August 2017.
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[I-D.ietf-spring-ipv6-use-cases]
Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R., and
M. Townsley, "IPv6 SPRING Use Cases", draft-ietf-spring-
ipv6-use-cases-11 (work in progress), June 2017.
[I-D.xu-mpls-unified-source-routing-instruction]
Xu, X., Filsfils, C., Bashandy, A., Raszuk, R., Chunduri,
U., Contreras, L., Jalil, L., Assarpour, H., Velde, G.,
Tantsura, J., Ma, S., and T. Mizrahi, "Unified Source
Routing Instructions using MPLS Label Stack", draft-xu-
mpls-unified-source-routing-instruction-03 (work in
progress), August 2017.
[RFC2992] Hopps, C., "Analysis of an Equal-Cost Multi-Path
Algorithm", RFC 2992, DOI 10.17487/RFC2992, November 2000,
<https://www.rfc-editor.org/info/rfc2992>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005, <https://www.rfc-
editor.org/info/rfc3985>.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
<https://www.rfc-editor.org/info/rfc4023>.
Authors' Addresses
Stewart Bryant (editor)
Huawei
Email: stewart.bryant@gmail.com
Adrian Farrel (editor)
Juniper Networks
Email: afarrel@juniper.net
John Drake
Juniper Networks
Email: jdrake@juniper.net
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Jeff Tantsura
Individual
Email: jefftant.ietf@gmail.com
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