Network Working Group F. Templin, Ed.
Internet-Draft Boeing Research & Technology
Intended status: Standards Track A. Whyman
Expires: February 22, 2020 MWA Ltd c/o Inmarsat Global Ltd
August 21, 2019
Transmission of IPv6 Packets over Aeronautical ("aero") Interfaces
draft-templin-atn-aero-interface-06.txt
Abstract
Mobile nodes (e.g., aircraft of various configurations) communicate
with networked correspondents over multiple access network data links
and configure mobile routers to connect their on-board networks.
Mobile nodes connect to access networks using either the classic or
mobility service-enabled link model. This document specifies the
transmission of IPv6 packets over aeronautical ("aero") interfaces.
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). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on February 22, 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
(https://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 Section 4.e of
Templin & Whyman Expires February 22, 2020 [Page 1]
Internet-Draft IPv6 over AERO Interfaces August 2019
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Aeronautical ("aero") Interface Model . . . . . . . . . . . . 4
5. Maximum Transmission Unit . . . . . . . . . . . . . . . . . . 6
6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Link-Local Addresses . . . . . . . . . . . . . . . . . . . . 6
8. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 8
9. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 11
10. Address Mapping for IPv6 Neighbor Discovery Messages . . . . 11
11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 12
11.1. Multiple Aero Interfaces . . . . . . . . . . . . . . . . 12
12. Router Discovery and Prefix Registration . . . . . . . . . . 13
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
14. Security Considerations . . . . . . . . . . . . . . . . . . . 16
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
16.1. Normative References . . . . . . . . . . . . . . . . . . 17
16.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. Aero Registration Option Extensions for Special-
Purpose Links . . . . . . . . . . . . . . . . . . . 19
Appendix B. Prefix Length Considerations . . . . . . . . . . . . 20
Appendix C. VDL Mode 2 Considerations . . . . . . . . . . . . . 20
Appendix D. RS/RA Messaging as the Single Standard API . . . . . 22
Appendix E. Change Log . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
Mobile Nodes (MNs) such as aircraft of various configurations may
have multiple data links for communicating with networked
correspondents. These data links often have differing performance,
cost and availability characteristics that can change dynamically
according to mobility patterns, flight phases, proximity to
infrastructure, etc.
Each MN receives an IPv6 Mobile Network Prefix (MNP) that can be used
by on-board networks independently of the access network data links
selected for data transport. The MN performs router discovery the
same as for customer edge routers [RFC7084], and acts as a mobile
router on behalf of its on-board networks. The MN connects to access
networks using either the classic [RFC4861] or Mobility Service (MS)-
enabled link model.
Templin & Whyman Expires February 22, 2020 [Page 2]
Internet-Draft IPv6 over AERO Interfaces August 2019
In the classic model, all IPv6 Neighbor Discovery (IPv6 ND) messaging
is directly over native access network interfaces managed according
to the weak end system model. The MN discovers neighbors on the link
through link-scoped multicast and/or unicast transmissions that map
to their corresponding link layer addresses per standard address
resolution / mapping procedures. The MN then coordinates with
mobility agents located in the larger Internetwork beyond the first-
hop access links by employing an on-board mobility function. This
arrangement requires the MN to engage in active mobility messaging on
its own behalf and with no assistance from the access network.
In the MS-enabled model, a virtual interface (termed the "aero
interface") is configured as a thin layer over the underlying access
network interfaces. The aero interface is therefore the only
interface abstraction exposed to the IPv6 layer and behaves according
to the Non-Broadcast, Multiple Access (NBMA) interface principle,
while underlying access network interfaces appear as link layer
communication channels in the architecture. The aero interface
connects to a virtual overlay cloud service known as the "aero link".
Each aero link has one or more associated Mobility Service Prefixes
(MSPs) that identify the link. An MSP is an aggregated IPv6 prefix
from which aero link MNPs are derived. If the MN connects to
multiple aero links, then it configures a separate aero interface for
each link.
The aero interface interacts with the ground-domain MS through IPv6
ND control message exchanges [RFC4861]. The MS tracks MN movements
and represents their MNPs in a global routing or mapping system.
The aero interface provides a traffic engineering nexus for guiding
inbound and outbound traffic to the correct underlying interface(s).
The IPv6 layer sees the aero interface as a point of connection to
the aero link; if there are multiple aero links (i.e., multiple
MS's), the IPv6 layer will see multiple aero interfaces.
This document specifies the transmission of IPv6 packets [RFC8200]
and MN/MS control messaging over aeronautical ("aero") interfaces in
the MS-enabled link model, and also includes all necessary details
for MN operation in the classic link model.
2. Terminology
The terminology in the normative references applies; especially, the
terms "link" and "interface" are the same as defined in the IPv6
[RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications.
The following terms are defined within the scope of this document:
Templin & Whyman Expires February 22, 2020 [Page 3]
Internet-Draft IPv6 over AERO Interfaces August 2019
Access Network (ANET)
a data link service network (e.g., an aviation radio access
network, satellite service provider network, cellular operator
network, etc.) protected by physical and/or link layer security.
Each ANET connects to outside Internetworks via border security
devices such as proxys, firewalls, packet filtering gateways, etc.
ANET interface
a node's attachment to a link in an ANET.
Internetwork (INET)
a connected network region with a coherent IP addressing plan that
provides transit forwarding services for ANET mobile nodes and
INET correspondents. Examples include private enterprise
networks, aviation networks and the global public Internet itself.
INET interface
a node's attachment to a link in an INET.
aero link
a virtual overlay cloud service configured over one or more INETs
and their connected ANETs. An aero link may comprise multiple
segments joined by bridges the same as for any link; the
addressing plans in each segment may be mutually exclusive and
managed by different administrative entities.
aero interface
a node's attachment to an aero link, and configured over one or
more underlying ANET/INET interfaces.
aero address
an IPv6 link-local address constructed as specified in Section 7,
and assigned to an aero interface.
3. Requirements
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]. Lower case
uses of these words are not to be interpreted as carrying RFC2119
significance.
4. Aeronautical ("aero") Interface Model
An aero interface is a MN virtual interface configured over one or
more ANET interfaces, which may be physical (e.g., an aeronautical
radio link) or virtual (e.g., an Internet or higher-layer "tunnel").
The MN coordinates with the MS through IPv6 ND message exchanges.
Templin & Whyman Expires February 22, 2020 [Page 4]
Internet-Draft IPv6 over AERO Interfaces August 2019
The aero interface architectural layering model is the same as in
[RFC7847], and augmented as shown in Figure 1. The IPv6 layer
therefore sees the aero interface as a single network layer interface
with multiple underlying ANET interfaces that appear as link layer
communication channels in the architecture.
+----------------------------+
| TCP/UDP |
Session-to-IP +---->| |
Address Binding | +----------------------------+
+---->| IPv6 |
IP Address +---->| |
Binding | +----------------------------+
+---->| aero Interface |
Logical-to- +---->| (aero address) |
Physical | +----------------------------+
Interface +---->| L2 | L2 | | L2 |
Binding |(IF#1)|(IF#2)| ..... |(IF#n)|
+------+------+ +------+
| L1 | L1 | | L1 |
| | | | |
+------+------+ +------+
Figure 1: Aero Interface Architectural Layering Model
The aero virtual interface model gives rise to a number of
opportunities:
o since aero interface link-local addresses are uniquely derived
from an MNP (see: Section 7, no Duplicate Address Detection (DAD)
messaging is necessary over the aero interface.
o ANET interfaces can remain unnumbered in environments where
communications are coordinated entirely over the aero interface.
o as ANET interface properties change (e.g., link quality, cost,
availability, etc.), any active ANET interface can be used to
update the profiles of multiple additional ANET interfaces in a
single message. This allows for timely adaptation and service
continuity under dynamically changing conditions.
o coordinating ANET interfaces in this way allows them to be
represented in a unified MS profile with provisions for mobility
and multilink operations.
o exposing a single virtual interface abstraction to the IPv6 layer
allows for traffic engineering (including QoS based link
selection, packet replication, load balancing, etc.) at the link
Templin & Whyman Expires February 22, 2020 [Page 5]
Internet-Draft IPv6 over AERO Interfaces August 2019
layer while still permitting queuing at the IPv6 layer based on,
e.g., traffic class, flow label, etc.
o the IPv6 layer sees the aero interface as a point of connection to
the aero link; if there are multiple aero links (i.e., multiple
MS's), the IPv6 layer will see multiple aero interfaces.
Other opportunities are discussed in [RFC7847].
5. Maximum Transmission Unit
All IPv6 interfaces MUST configure an MTU of at least 1280 bytes
[RFC8200], while the aero interface configures an MTU based on the
largest MTU among all underlying ANET interfaces.
The aero interface returns internally-generated IPv6 Path MTU
Discovery (PMTUD) Packet Too Big (PTB) messages [RFC8201] for packets
admitted into the aero interface that are too large for the outbound
underlying ANET interface. Similarly, the aero interface performs
PMTUD even if the destination appears to be on the same link since a
proxy on the path could return a PTB message. PMTUD therefore
ensures that the aero interface MTU is adaptive and reflects the
current path used for a given data flow.
Applications that cannot tolerate loss due to MTU restrictions should
refrain from sending packets larger than 1280 bytes, since dynamic
path changes can reduce the path MTU at any time.
6. Frame Format
The aero interface transmits IPv6 packets according to the native
frame format of each underlying ANET interface. For example, for
Ethernet-compatible interfaces the frame format is specified in
[RFC2464], for aeronautical radio interfaces the frame format is
specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical
Manual), for tunnels over IPv6 the frame format is exactly as
specified in [RFC2473], etc.
7. Link-Local Addresses
A MN "aero address" is an IPv6 link-local address with an interface
identifier based on its assigned MNP. MN aero addresses begin with
the prefix fe80::/64 followed by a 64-bit prefix taken from the MNP
(see: Appendix B). For example, for the MNP:
2001:db8:1000:2000::/56
the corresponding aero addresses are:
Templin & Whyman Expires February 22, 2020 [Page 6]
Internet-Draft IPv6 over AERO Interfaces August 2019
fe80::2001:db8:1000:2000
fe80::2001:db8:1000:2001
fe80::2001:db8:1000:2002
... etc. ...
fe80::2001:db8:1000:20ff
When the MN configures aero addresses from its MNP, it assigns them
to each ANET interface (and also to the aero interface in the MS-
enabled model). The lowest-numbered aero address serves as the
"base" address (for example, for the MNP 2001:db8:1000:2000::/56 the
base aero address is fe80::2001:db8:1000:2000). The MN uses the base
aero address for IPv6 ND messaging, but accepts packets destined to
all aero addresses equally (i.e., the same as for any multi-addressed
IPv6 interface).
In the MS-enabled link model, MS endpoint (MSE) aero addresses are
allocated from the range fe80::/96, and MUST be managed for
uniqueness by the collective aero link administrative authorities.
The lower 32 bits of the address includes a unique integer value,
e.g., fe80::1, fe80::2, fe80::3, etc. The address fe80::ffff:ffff is
reserved and the address fe80:: is the IPv6 link-local Subnet Router
Anycast address [RFC4291]; hence, these values are not available for
general assignment.
In the classic link model, ANET link devices number their interfaces
from the range fe80::/96 the same as above except that these
addresses need not be managed for uniqueness outside of the local
ANET link. It is therefore possible that different ANET links could
reuse numbers from the fe80::/96 space since the addresses are link-
scope only.
In a mixed model, both the classic and MS-enabled numbering schemes
can be used without conflict within the same ANET, as the two
services would be conducted as ships in the night. A mix of MNs
operating according to classic and MS-enabled models could then
operate within the same ANETs without interference.
Since MN aero addresses are guaranteed unique by the nature of the
unique MNP delegation, aero interfaces set the autoconfiguration
variable DupAddrDetectTransmits to 0 [RFC4862].
Templin & Whyman Expires February 22, 2020 [Page 7]
Internet-Draft IPv6 over AERO Interfaces August 2019
8. Address Mapping - Unicast
Aero interfaces maintain a neighbor cache for tracking per-neighbor
state the same as for any IPv6 interface and use the link-local
address format specified in Section 7. IPv6 Neighbor Discovery (ND)
[RFC4861] messages on aero interfaces use the native Source/Target
Link-Layer Address Option (S/TLLAO) formats of the underlying ANET
interfaces (e.g., for Ethernet the S/TLLAO is specified in
[RFC2464]).
MNs such as aircraft typically have many wireless data link types
(e.g. satellite-based, cellular, terrestrial, air-to-air directional,
etc.) with diverse performance, cost and availability properties.
The aero interface would therefore appear to have multiple link layer
connections, and may include information for multiple ANET interfaces
in a single message exchange.
Aero interfaces use a new IPv6 ND options called the "Aero
Registration (AR)" option. MNs that wish to invoke the MS include
the AR option in Router Solicitation (RS) and/or unsolicited Neighbor
Advertisement (uNA) messages to request registration/deregistration,
and the MS includes the AR option in Router Advertisement (RA)
messages to acknowledge the MN's registration/deregistration.
AR options in a MN's RS/uNA messages are formatted as shown in
Figure 2:
Templin & Whyman Expires February 22, 2020 [Page 8]
Internet-Draft IPv6 over AERO Interfaces August 2019
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Prefix Length |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ifIndex [1] |P00|P01|P02|P03|P04|P05|P06|P07|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P56|P57|P58|P59|P60|P61|P62|P63| ifIndex [2] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... | ifIndex [N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Trailing zero padding (0 - 6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Aero Registration (AR) Option Format in RS/uNA Messages
In this format:
o Type is set to TBD.
Templin & Whyman Expires February 22, 2020 [Page 9]
Internet-Draft IPv6 over AERO Interfaces August 2019
o Length is set to the number of 8 octet blocks in the option (with
trailing zero padding added if necessary to produce an integral
number of 8 octet blocks).
o Prefix Length is set to the length of the MNP embedded in the MN's
aero address.
o R (the "Register" bit) is set to '1' to sustain the MNP
registration or set to '0' to request de-registration.
o Reserved is set to the value '0' on transmission.
o Nonce is set to a (pseudo)-random 32-bit value selected by the MN,
and used to correlate received confirmations.
o A list of N (ifIndex[i], P[i])-tuples are included as follows:
* ifIndex[i] [RFC2863] is set to a 16-bit integer value
corresponding to a specific underlying ANET interface. The
first ifIndex MUST correspond to the ANET interface over which
the message is sent. Once the MN has assigned an ifIndex to an
ANET interface, the assignment MUST remain unchanged until the
MN disables the interface. MNs MUST number each ifIndex with a
value between '1' and '0xffff'.
* P[i] is a per-ifIndex set of Preferences that correspond to the
64 Differentiated Service Code Point (DSCP) values [RFC2474]
pertaining to the ANET interface. Each (P00 - P63) field is
set to the value '0' ("disabled"), '1' ("low"), '2' ("medium")
or '3' ("high") to indicate a QoS preference level for ANET
interface selection purposes.
AR options in the MS RA replies are formatted as shown in Figure 3:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = 2 | Prefix Length |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Aero Registration (AR) Option Format in RA messages
Templin & Whyman Expires February 22, 2020 [Page 10]
Internet-Draft IPv6 over AERO Interfaces August 2019
In this format:
o Type is set to TBD.
o Length is set to the constant value '2' (i.e., 2 units of 8
octets).
o Prefix Length is set to the length included in the AR option of
the RS message that triggered the RA response.
o R is set to '1' to confirm registration or set to '0' to release/
decline registration.
o Reserved is set to the value '0' on transmission.
o Nonce echoes the 32 bit value received in the AR option of the
corresponding RS message.
o Prefix Lifetime is set to the time in seconds that the MSE will
maintain the Prefix registration.
9. Address Mapping - Multicast
The multicast address mapping of the native underlying ANET interface
applies. The mobile router on board the aircraft also serves as an
IGMP/MLD Proxy for its EUNs and/or hosted applications per [RFC4605]
while using the link layer address of the router as the link layer
address for all multicast packets.
10. Address Mapping for IPv6 Neighbor Discovery Messages
Per [RFC4861], IPv6 ND messages may be sent to either a multicast or
unicast link-scoped IPv6 destination address. For aero interfaces in
the MS-enabled model, however, IPv6 ND messaging must be coordinated
between the MN and MS only without invoking other nodes on the ANET.
For this reason, ANET links maintain one or more unicast link-layer
address ("MSADDR") for the purpose of supporting MN/MS IPv6 ND
messaging. For Ethernet-compatible ANETs, this specification
reserves one Ethernet unicast address 00-00-5E-00-52-14. For non-
Ethernet statically-addressed ANETs, MSADDR is reserved per the
assigned numbers authority for the ANET addressing space. On still
other links, one or more MSADDR is discovered through dynamic link-
layer beacons received from ANET access routers.
MNs operating according to the MS-enabled model map all IPv6 ND
messages they send (i.e., both multicast and unicast) to an MSADDR
instead of to an ordinary unicast or multicast link-layer address.
Templin & Whyman Expires February 22, 2020 [Page 11]
Internet-Draft IPv6 over AERO Interfaces August 2019
In this way, all of the MN's IPv6 ND messages will be received by MS
devices that are configured to accept packets destined to MSADDR
(i.e., a point-to-point neighbor model). Note that multiple MS
devices on the link could be configured to accept packets destined to
MSADDR, e.g., as a basis for virtual router redundancy.
Therefore, ANET access routers MUST accept and process packets
destined to MSADDR, while all other devices MUST NOT process packets
destined to MSADDR. This model has a well-established operational
experience in Proxy Mobile IPv6 (PMIP) [RFC5213][RFC6543].
11. Conceptual Sending Algorithm
The MN's IPv6 layer selects the outbound aero interface according to
standard IPv6 requirements. The aero interface maintains default
routes and neighbor cache entries for MSEs, and may also include
additional neighbor cache entries created through other means (e.g.,
Address Resolution, static configuration, etc.).
When the MN sends an NS message for Address Resolution, the aero
interface forwards the message to an MSE (see: Section 12) which acts
as a link-layer forwarding agent according to the NBMA link model.
The resulting NA message will provide link-layer address information
for the neighbor. When Neighbor Unreachability Detection is used,
the NS/NA exchange confirms reachability the same as for any IPv6
interface.
After a packet enters the aero interface, an outbound ANET interface
is selected based on traffic engineering information such as DSCP,
application port number, cost, performance, etc. Aero interface
traffic engineering could also be configured to perform replication
across multiple ANET interfaces for increased reliability at the
expense of packet duplication.
When a target neighbor has multiple link-layer addresses (each with a
different traffic engineering profile), the aero interface selects
ANET interfaces and neighbor link-layer addresses according to both
its own outbound preferences and the inbound preferences of the
target neighbor.
11.1. Multiple Aero Interfaces
MNs may associate with multiple MS instances concurrently. Each MS
instance represents a distinct aero link distinguished by its
associated MSPs. The MN configures a separate aero interface for
each link so that multiple interfaces (e.g., aero0, aero1, aero2,
etc.) are exposed to the IPv6 layer.
Templin & Whyman Expires February 22, 2020 [Page 12]
Internet-Draft IPv6 over AERO Interfaces August 2019
Depending on local policy and configuration, an MN may choose between
alternative active aero interfaces using a packet's DSCP, routing
information or static configuration. In particular, the MN can add
the MSPs received in Prefix Information Options (PIOs) [RFC4861]
[RFC8028] as guidance for aero interface selection based on per-
packet source addresses.
Each aero interface can be configured over the same or different sets
of ANET interfaces. Each ANET distinguishes between the different
aero links based on the MSPs represented in per-packet IPv6
addresses.
Multiple distinct aero links can therefore be used to support fault
tolerance, load balancing, reliability, etc. The architectural model
parallels Layer 2 Virtual Local Area Networks (VLANs), where the MSPs
serve as (virtual) VLAN tags.
12. Router Discovery and Prefix Registration
ANET access routers accept IPv6 ND messages destined to the link-
local Subnet Router Anycast Address (fe80::), all-routers multicast
and any unicast link-local IPv6 addresses they are configured to
listen to. ANET access routers that support the classic link model
configure link-local addresses that are guaranteed not to conflict
with MN link-local addresses as discussed in Section 7. ANET access
routers that support the MS-enabled model configure the link-layer
address MSADDR (see: Section 10) and act as proxies for all MSEs from
the range fe80::1 through fe80::ffff:fffe.
MNs that support the classic model perform ordinary RS/RA exchanges
over each ANET the same as for ordinary IPv6 links. ANET access
routers send RAs with an IPv6 link-local source address from the
range fe80::1 through fe80::ffff:fffe that is guaranteed not to
conflict with the MN's aero address nor the address of any other
routers on the link. The RA messages include normal configuration
options including prefix information, MTU, etc. The MNs are then
responsible for coordinating their ANET interfaces on their own
behalf and for coordinating with any INET-based mobility agents. No
further support from the ANET is needed.
MNs that support the MS-enabled model interface with the MS by
sending RS messages with AR options. For each ANET interface, the MN
sends initial RS messages with AR options with link-layer address set
to MSADDR and with network-layer address set to either a specific MSE
address or to all-routers multicast. The ANET access router receives
the RS messages and contacts the corresponding MSE (when the
destination is all-routers multicast, the access router itself
selects an MSE). When the MSE responds, the ANET access router
Templin & Whyman Expires February 22, 2020 [Page 13]
Internet-Draft IPv6 over AERO Interfaces August 2019
returns RA messages with AR options and with any information for the
link that would normally be delivered in a solicited RA message.
Note that some ANET access routers that listen on MSADDR may not be
configured to recognize and/or process AR options. Those access
routers must still obey the requirements of [RFC4861] that state:
"Future versions of this protocol may define new option types.
Receivers MUST silently ignore any options they do not recognize
and continue processing the message."
In that case, the access router processes the RS message and returns
an RA message according to the classic link model including any
configuration options but without including an AR option. Upon
receiving the RA message, the MN must manage this ANET interface
according to the classic link model and must not configure it as an
underlying interface of the aero interface.
MNs configure aero interfaces that observe the properties discussed
in the previous section. The aero interface and its underlying
interfaces are said to be in either the "UP" or "DOWN" state
according to administrative actions in conjunction with the interface
connectivity status. An aero interface transitions to UP or DOWN
through administrative action and/or through state transitions of the
underlying interfaces. When a first underlying interface transitions
to UP, the aero interface also transitions to UP. When all
underlying interfaces transition to DOWN, the aero interface also
transitions to DOWN.
When an aero interface transitions to UP, the MN sends initial RS
messages to register its MNP and an initial set of underlying ANET
interfaces that are also UP. The MN sends additional RS messages to
refresh lifetimes and to register/deregister underlying ANET
interfaces as they transition to UP or DOWN.
MS-enabled ANET access routers coordinate with the MSE and send RA
messages with configuration information in response to a MN's RS
messages. The RA includes a Router Lifetime value and PIOs with (A;
L=0) that include MSPs for the link. The configuration information
may also include Route Information Options (RIO) options [RFC4191]
with more-specific routes, and an MTU option that specifies the
maximum acceptable packet size for the link. The ANET access router
sends immediate unicast RA responses without delay; therefore, the
'MAX_RA_DELAY_TIME' and 'MIN_DELAY_BETWEEN_RAS' constants for
multicast RAs do not apply. The ANET access router MAY send periodic
and/or event-driven unsolicited RA messages, but is not required to
do so for unicast advertisements [RFC4861].
Templin & Whyman Expires February 22, 2020 [Page 14]
Internet-Draft IPv6 over AERO Interfaces August 2019
The MN sends RS messages from within the aero interface while using
an UP underlying ANET interface as the outbound interface. Each RS
message is formatted as though it originated from the IPv6 layer, but
the process is coordinated wholly from within the aero interface and
is therefore opaque to the IPv6 layer. The MN sends initial RS
messages over an UP underlying interface with its aero address as the
source and the address of an MSE as the destination. The RS messages
include AR options with a valid Prefix Length as well as ifIndex and
P(i) values appropriate for underlying ANET interfaces. The MS-
enabled ANET access router processes RS message and forwards the
information in the AR option to the MSE.
When the MSE processes the AR information, if the prefix registration
was accepted the MSE injects the MNP into the routing/mapping system
then caches the new Prefix Length, MNP, ifIndex and P(i) values. The
MSE then returns a non-zero Prefix Lifetime if the prefix assertion
was acceptable; otherwise, with a zero Prefix Lifetime. The ANET
access router then returns an RA message with an AR option to the MN.
When the MN receives the RA message, it creates a default route with
next hop address set to the MSE found in the RA source address and
with link-layer address set to MSADDR. The ANET access router will
then forward packets acting as a proxy between the MN and the actual
MSE.
The MN then manages its underlying ANET interfaces according to their
states as follows:
o When an underlying ANET interface transitions to UP, the MN sends
an RS over the ANET interface with an AR option. The AR option
contains a first ifIndex-tuple with values appropriate for this
ANET interface, and may contain additional ifIndex-tuples
appropriate for other ANET interfaces.
o When an underlying ANET interface transitions to DOWN, the MN
sends an RS/uNA message over any UP ANET interface with an AR
option containing an ifIndex-tuple for the DOWN ANET interface
with all P(i) values set to '0'. The MN sends an RS when an
acknowledgement is required, or an uNA when reliability is not
thought to be a concern (e.g., if redundant transmissions are sent
on multiple ANET interfaces).
o When a MN wishes to release from the current MSE, it sends an RS
message over any UP ANET interface with an AR option with R set to
0. The corresponding MSE then withdraws the MNP from the routing/
mapping system and returns an RA message with an AR option with
Prefix Lifetime set to 0.
Templin & Whyman Expires February 22, 2020 [Page 15]
Internet-Draft IPv6 over AERO Interfaces August 2019
o When all of a MNs underlying interfaces have transitioned to DOWN,
the MSE withdraws the MNP the same as if it had received a message
with an AR option with R set to 0.
The MN is responsible for retrying each RS exchange up to
MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL
seconds until an RA is received. If no RA is received over multiple
UP ANET interfaces, the MN declares this MSE unreachable and tries a
different MSE.
The IPv6 layer sees the aero interface as an ordinary IPv6 interface.
Therefore, when the IPv6 layer sends an RS message the aero interface
returns an internally-generated RA message as though the message
originated from an IPv6 router. The internally-generated RA message
contains configuration information (such as Router Lifetime, MTU,
etc.) that is consistent with the information received from the RAs
generated by the MS.
Whether the aero interface IPv6 ND messaging process is initiated
from the receipt of an RS message from the IPv6 layer is an
implementation matter. Some implementations may elect to defer the
IPv6 ND messaging process until an RS is received from the IPv6
layer, while others may elect to initiate the process independently
of any IPv6 layer messaging.
13. IANA Considerations
The IANA is instructed to allocate an official Type number from the
IPv6 Neighbor Discovery Option Formats registry for the Aero
Registration (AR) option. Implementations set Type to 253 as an
interim value [RFC4727].
The IANA is instructed to allocate one Ethernet unicast address,
00-00-5E-00-52-14 [RFC5214] in the registry "IANA Ethernet Address
Block - Unicast Use".
14. Security Considerations
Security considerations are the same as defined for the specific
access network interface types, and readers are referred to the
appropriate interface specifications.
IPv6 and IPv6 ND security considerations also apply, and are
specified in the normative references.
Templin & Whyman Expires February 22, 2020 [Page 16]
Internet-Draft IPv6 over AERO Interfaces August 2019
15. Acknowledgements
This document was prepared per the consensus decision at the 8th
Conference of the International Civil Aviation Organization (ICAO)
Working Group-I Mobility Subgroup on March 22, 2019. Attendees and
contributors included: Guray Acar, Danny Bharj, Francois D'Humieres,
Pavel Drasil, Nikos Fistas, Giovanni Garofolo, Vaughn Maiolla, Tom
McParland, Victor Moreno, Madhu Niraula, Brent Phillips, Liviu
Popescu, Jacky Pouzet, Aloke Roy, Greg Saccone, Robert Segers,
Stephane Tamalet, Fred Templin, Bela Varkonyi, Tony Whyman, and
Dongsong Zeng.
The following individuals are acknowledged for their useful comments:
Pavel Drasil, Zdenek Jaron, Michael Matyas, Madhu Niraula, Greg
Saccone.
.
16. References
16.1. Normative References
[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>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
November 2005, <https://www.rfc-editor.org/info/rfc4191>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
ICMPv6, UDP, and TCP Headers", RFC 4727,
DOI 10.17487/RFC4727, November 2006,
<https://www.rfc-editor.org/info/rfc4727>.
Templin & Whyman Expires February 22, 2020 [Page 17]
Internet-Draft IPv6 over AERO Interfaces August 2019
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.
[RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by
Hosts in a Multi-Prefix Network", RFC 8028,
DOI 10.17487/RFC8028, November 2016,
<https://www.rfc-editor.org/info/rfc8028>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>.
16.2. Informative References
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<https://www.rfc-editor.org/info/rfc2464>.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <https://www.rfc-editor.org/info/rfc2473>.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
<https://www.rfc-editor.org/info/rfc2863>.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605,
August 2006, <https://www.rfc-editor.org/info/rfc4605>.
Templin & Whyman Expires February 22, 2020 [Page 18]
Internet-Draft IPv6 over AERO Interfaces August 2019
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008,
<https://www.rfc-editor.org/info/rfc5213>.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
DOI 10.17487/RFC5214, March 2008,
<https://www.rfc-editor.org/info/rfc5214>.
[RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for
Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May
2012, <https://www.rfc-editor.org/info/rfc6543>.
[RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
Requirements for IPv6 Customer Edge Routers", RFC 7084,
DOI 10.17487/RFC7084, November 2013,
<https://www.rfc-editor.org/info/rfc7084>.
[RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S.,
Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit
Boundary in IPv6 Addressing", RFC 7421,
DOI 10.17487/RFC7421, January 2015,
<https://www.rfc-editor.org/info/rfc7421>.
[RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface
Support for IP Hosts with Multi-Access Support", RFC 7847,
DOI 10.17487/RFC7847, May 2016,
<https://www.rfc-editor.org/info/rfc7847>.
Appendix A. Aero Registration Option Extensions for Special-Purpose
Links
Adaptation of the aero interface to the Aeronautical
Telecommunications Network with Internet Protocol Services (ATN/IPS)
includes link selection preferences based on transport port numbers
in addition to the existing DSCP-based preferences. ATN/IPS nodes
maintain a map of transport port numbers to 64 possible preference
fields, e.g., TCP port 22 maps to preference field 8, TCP port 443
maps to preference field 20, UDP port 8060 maps to preference field
34, etc. The extended aero registration option format for ATN/IPS is
shown in Figure 4, where the 'Q(i)' fields provide link preferences
for the corresponding transport port number.
Templin & Whyman Expires February 22, 2020 [Page 19]
Internet-Draft IPv6 over AERO Interfaces August 2019
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Prefix Length |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ifIndex [1] |P00|P01|P02|P03|P04|P05|P06|P07|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P56|P57|P58|P59|P60|P61|P62|P63|Q00|Q01|Q02|Q03|Q04|Q05|Q06|Q07|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Q08|Q09|Q10|Q11|Q12|Q13|Q14|Q15|Q16|Q17|Q18|Q19|Q20|Q21|Q22|Q23|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Q24|Q25|Q26|Q27|Q28|Q29|Q30|Q31|Q32|Q33|Q34|Q35|Q36|Q37|Q38|Q39|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Q40|Q41|Q42|Q43|Q44|Q45|Q46|Q47|Q48|Q49|Q50|Q51|Q52|Q53|Q54|Q55|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Q56|Q57|Q58|Q59|Q60|Q61|Q62|Q63| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: ATN/IPS Extended Aero Option Format
Appendix B. Prefix Length Considerations
The IPv6 addressing architecture [RFC4291] reserves the prefix ::/8;
this assures that MNPs will not begin with ::32 so that MN and MS
aero addresses cannot overlap. Additionally, this specification
currently observes the 64-bit boundary in IPv6 addresses [RFC7421].
MN aero addresses insert the most-significant 64 MNP bits into the
least-significant 64 bits of the prefix fe80::/64, however [RFC4291]
defines the link-local prefix as fe80::/10 meaning "fe80" followed by
54 unused bits followed by the least-significant 64 bits of the
address. Future versions of this specification may adapt the 54
unused bits for extended coding of MNP prefixes of /65 or longer (up
to /118).
Appendix C. VDL Mode 2 Considerations
ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2"
(VDLM2) that specifies an essential radio frequency data link service
for aircraft and ground stations in worldwide civil aviation air
Templin & Whyman Expires February 22, 2020 [Page 20]
Internet-Draft IPv6 over AERO Interfaces August 2019
traffic management. The VDLM2 link type is "multicast capable"
[RFC4861], but with considerable differences from common multicast
links such as Ethernet and IEEE 802.11.
First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of
magnitude less than most modern wireless networking gear. Second,
due to the low available link bandwidth only VDLM2 ground stations
(i.e., and not aircraft) are permitted to send broadcasts, and even
so only as compact layer 2 "beacons". Third, aircraft employ the
services of ground stations by performing unicast RS/RA exchanges
upon receipt of beacons instead of listening for multicast RA
messages and/or sending multicast RS messages.
This beacon-oriented unicast RS/RA approach is necessary to conserve
the already-scarce available link bandwidth. Moreover, since the
numbers of beaconing ground stations operating within a given spatial
range must be kept as sparse as possible, it would not be feasible to
have different classes of ground stations within the same region
speaking different protocols. It is therefore highly desirable that
all ground stations speak a common language of RS/RA as specified in
this document.
An aircraft that encounters a beaconing ground station can elect to
solicit either the classic or MS-enabled link models discussed in
Section 12. If the aircraft employs the classic link model, it sends
an RS message with no AR option. The ground station will return an
RA message with no AR option along with any configuration options for
the link (e.g., prefix information, MTU, etc.). If the aircraft
wishes to engage the MS-enabled model, it instead sends an RS message
with an AR option.
Upon receipt of an RS message with an AR option, the ground station
proceeds according to the MS-enabled model if it is configured to do
so. If the ground station does not recognize the AR option (or, if
it is not configured for MS-enabled operation) it instead ignores the
option and processes the rest of the RS message per [RFC4861].
This flexibility notwithstanding, VDLM2 ground stations must be
consistent in terms of the service they offer. In particular, while
it is permissible for a ground station to simultaneously offer
different link models to different aircraft, it should not switch
between the classic and MS-enabled operating models for ongoing RS/RA
exchanges with the same aircraft.
Templin & Whyman Expires February 22, 2020 [Page 21]
Internet-Draft IPv6 over AERO Interfaces August 2019
Appendix D. RS/RA Messaging as the Single Standard API
At the ICAO Working Group I Mobility Subgroup meeting in London, July
8-12, 2019 an assertion was made that the MS-enabled link model must
employ a different message type besides RS/RA. This was based on the
pretext that including a new IPv6 ND option in an RS message would
cause routers that do not recognize the option to do "strange
things". However, [RFC4861] assures that no standards-compliant
router would have trouble processing an RS with unrecognized options
due to the following Section 4.1 requirement:
"Future versions of this protocol may define new option types.
Receivers MUST silently ignore any options they do not recognize
and continue processing the message."
Indeed, this same normative requirement appeared in both RFC2461 and
RFC1970 (the predecessors of RFC2460) dating back to August 1996.
Therefore, any router that refused to continue processing an RS
message after encountering a properly-formed but unrecognized option
would not be standards-compliant and should not be used in any
production network capacity.
Assuming for a moment however that a new message type were used to
invoke the MS-enabled link model, this would require two message
exchanges between the MN and ANET access router - a first exchange
with RS/RA with no new IPv6 ND options, and a second exchange with
the new message type. However, on links such as VDLM2 (see:
Appendix C) the addition of a second message exchange would impart
unacceptable delay in closing the link and unacceptable extraneous
message overhead that impacts link capacity for all. This clearly
indicates a need to include all link establishment signaling in a
single message exchange and not multiple.
We therefore see strong motivation for including a new IPv6 ND option
in RS/RA messages instead of creating a new message type, and proof
that doing so will not harm standards-compliant access routers.
Routers that recognize the options can at their discretion either
honor or ignore them, while assuring that the MN will be provided
with either its first choice or second choice link model. However,
service providers that do not offer MN customers their first choice
may risk losing business to others that do.
Appendix E. Change Log
<< RFC Editor - remove prior to publication >>
Differences from draft-templin-atn-aero-interface-05 to draft-
templin-atn-aero-interface-06:
Templin & Whyman Expires February 22, 2020 [Page 22]
Internet-Draft IPv6 over AERO Interfaces August 2019
o New Appendix C on "VDL Mode 2 Considerations"
o New Appendix D on "RS/RA Messaging as a Single Standard API"
o Various significant updates in Section 5, 10 and 12.
Differences from draft-templin-atn-aero-interface-04 to draft-
templin-atn-aero-interface-05:
o Introduced RFC6543 precedent for focusing IPv6 ND messaging to a
reserved unicast link-layer address
o Introduced new IPv6 ND option for Aero Registration
o Specification of MN-to-MSE message exchanges via the ANET access
router as a proxy
o IANA Considerations updated to include registration requests and
set interim RFC4727 option type value.
Differences from draft-templin-atn-aero-interface-03 to draft-
templin-atn-aero-interface-04:
o Removed MNP from aero option format - we already have RIOs and
PIOs, and so do not need another option type to include a Prefix.
o Clarified that the RA message response must include an aero option
to indicate to the MN that the ANET provides a MS.
o MTU interactions with link adaptation clarified.
Differences from draft-templin-atn-aero-interface-02 to draft-
templin-atn-aero-interface-03:
o Sections re-arranged to match RFC4861 structure.
o Multiple aero interfaces
o Conceptual sending algorithm
Differences from draft-templin-atn-aero-interface-01 to draft-
templin-atn-aero-interface-02:
o Removed discussion of encapsulation (out of scope)
o Simplified MTU section
Templin & Whyman Expires February 22, 2020 [Page 23]
Internet-Draft IPv6 over AERO Interfaces August 2019
o Changed to use a new IPv6 ND option (the "aero option") instead of
S/TLLAO
o Explained the nature of the interaction between the mobility
management service and the air interface
Differences from draft-templin-atn-aero-interface-00 to draft-
templin-atn-aero-interface-01:
o Updates based on list review comments on IETF 'atn' list from
4/29/2019 through 5/7/2019 (issue tracker established)
o added list of opportunities afforded by the single virtual link
model
o added discussion of encapsulation considerations to Section 6
o noted that DupAddrDetectTransmits is set to 0
o removed discussion of IPv6 ND options for prefix assertions. The
aero address already includes the MNP, and there are many good
reasons for it to continue to do so. Therefore, also including
the MNP in an IPv6 ND option would be redundant.
o Significant re-work of "Router Discovery" section.
o New Appendix B on Prefix Length considerations
First draft version (draft-templin-atn-aero-interface-00):
o Draft based on consensus decision of ICAO Working Group I Mobility
Subgroup March 22, 2019.
Authors' Addresses
Fred L. Templin (editor)
Boeing Research & Technology
P.O. Box 3707
Seattle, WA 98124
USA
Email: fltemplin@acm.org
Templin & Whyman Expires February 22, 2020 [Page 24]
Internet-Draft IPv6 over AERO Interfaces August 2019
Tony Whyman
MWA Ltd c/o Inmarsat Global Ltd
99 City Road
London EC1Y 1AX
England
Email: tony.whyman@mccallumwhyman.com
Templin & Whyman Expires February 22, 2020 [Page 25]