Network Working Group F. Templin, Ed.
Internet-Draft The Boeing Company
Updates: rfc4193, rfc4291, rfc4443, A. Whyman
rfc8201 (if approved) MWA Ltd c/o Inmarsat Global Ltd
Intended status: Standards Track June 2, 2020
Expires: December 4, 2020
Transmission of IPv6 Packets over Overlay Multilink Network (OMNI)
Interfaces
draft-templin-6man-omni-interface-24
Abstract
Mobile nodes (e.g., aircraft of various configurations, terrestrial
vehicles, seagoing vessels, enterprise wireless devices, etc.)
communicate with networked correspondents over multiple access
network data links and configure mobile routers to connect end user
networks. A multilink interface specification is therefore needed
for coordination with the network-based mobility service. This
document specifies the transmission of IPv6 packets over Overlay
Multilink Network (OMNI) Interfaces.
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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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 4, 2020.
Copyright Notice
Copyright (c) 2020 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 7
5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 10
5.1. Fragmentation Security Implications . . . . . . . . . . . 12
6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 13
8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 14
9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 15
9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 16
9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1.3. ifIndex-tuple (Type 1) . . . . . . . . . . . . . . . 17
9.1.4. ifIndex-tuple (Type 2) . . . . . . . . . . . . . . . 20
9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 20
9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 21
9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 21
9.1.8. Geo Coordiantes . . . . . . . . . . . . . . . . . . . 21
10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 22
11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 22
11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 23
12. Router Discovery and Prefix Registration . . . . . . . . . . 23
12.1. Multihop Router Discovery . . . . . . . . . . . . . . . 26
13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 27
14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 28
15. Detecting and Responding to MSE Failures . . . . . . . . . . 28
16. Transition Considerations . . . . . . . . . . . . . . . . . . 29
17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 29
18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 30
19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
20. Security Considerations . . . . . . . . . . . . . . . . . . . 31
21. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 32
22. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
22.1. Normative References . . . . . . . . . . . . . . . . . . 32
22.2. Informative References . . . . . . . . . . . . . . . . . 34
Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference
Encoding . . . . . . . . . . . . . . . . . . . . . . 38
Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 39
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Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 40
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
1. Introduction
Mobile Nodes (MNs) (e.g., aircraft of various configurations,
terrestrial vehicles, seagoing vessels, enterprise wireless devices,
etc.) often have multiple data links for communicating with networked
correspondents. These data links may have diverse performance, cost
and availability properties that can change dynamically according to
mobility patterns, flight phases, proximity to infrastructure, etc.
MNs coordinate their data links in a discipline known as "multilink",
in which a single virtual interface is configured over the underlying
data links.
The MN configures a virtual interface (termed the "Overlay Multilink
Network (OMNI) interface") as a thin layer over the underlying Access
Network (ANET) interfaces. The OMNI 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 interfaces appear as link layer communication
channels in the architecture. The OMNI interface connects to a
virtual overlay service known as the "OMNI link". The OMNI link
spans one or more Internetworks that may include private-use
infrastructures and/or the global public Internet itself.
Each MN receives a Mobile Network Prefix (MNP) for numbering
downstream-attached End User Networks (EUNs) independently of the
access network data links selected for data transport. The MN
performs router discovery over the OMNI interface (i.e., similar to
IPv6 customer edge routers [RFC7084]) and acts as a mobile router on
behalf of its EUNs. The router discovery process is iterated over
each of the OMNI interface's underlying interfaces in order to
register per-link parameters (see Section 12).
The OMNI interface provides a multilink nexus for exchanging inbound
and outbound traffic via the correct underlying interface(s). The
IPv6 layer sees the OMNI interface as a point of connection to the
OMNI link. Each OMNI link has one or more associated Mobility
Service Prefixes (MSPs) from which OMNI link MNPs are derived. If
there are multiple OMNI links, the IPv6 layer will see multiple OMNI
interfaces.
MNs may connect to multiple distinct OMNI links by configuring
multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI
interface is configured over a set of underlying interfaces and
provides a nexus for Safety-Based Multilink (SBM) operation. The IP
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layer selects an OMNI interface based on SBM routing considerations,
then the selected interface applies Performance-Based Multilink (PBM)
to select the correct underlying interface. Applications can apply
Segment Routing [RFC8402] to select independent SBM topologies for
fault tolerance.
The OMNI interface interacts with a network-based Mobility Service
(MS) through IPv6 Neighbor Discovery (ND) control message exchanges
[RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that
track MN movements and represent their MNPs in a global routing or
mapping system.
This document specifies the transmission of IPv6 packets [RFC8200]
and MN/MS control messaging over OMNI interfaces.
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.
Also, the Protocol Constants defined in Section 10 of [RFC4861] are
used in their same format and meaning in this document. The terms
"All-Routers multicast", "All-Nodes multicast" and "Subnet-Router
anycast" are the same as defined in [RFC4291] (with Link-Local scope
assumed).
The following terms are defined within the scope of this document:
Mobile Node (MN)
an end system with a mobile router having multiple distinct
upstream data link connections that are grouped together in one or
more logical units. The MN's data link connection parameters can
change over time due to, e.g., node mobility, link quality, etc.
The MN further connects a downstream-attached End User Network
(EUN). The term MN used here is distinct from uses in other
documents, and does not imply a particular mobility protocol.
End User Network (EUN)
a simple or complex downstream-attached mobile network that
travels with the MN as a single logical unit. The IPv6 addresses
assigned to EUN devices remain stable even if the MN's upstream
data link connections change.
Mobility Service (MS)
a mobile routing service that tracks MN movements and ensures that
MNs remain continuously reachable even across mobility events.
Specific MS details are out of scope for this document.
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Mobility Service Endpoint (MSE)
an entity in the MS (either singular or aggregate) that
coordinates the mobility events of one or more MN.
Mobility Service Prefix (MSP)
an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the
rest of the Internetwork by the MS, and from which more-specific
Mobile Network Prefixes (MNPs) are derived.
Mobile Network Prefix (MNP)
a longer IPv6 prefix taken from an MSP (e.g.,
2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate
the MNP to devices located in EUNs.
Access Network (ANET)
a data link service network (e.g., an aviation radio access
network, satellite service provider network, cellular operator
network, wifi network, etc.) that connects MNs. Physical and/or
data link level security between the MN and ANET are assumed.
Access Router (AR)
a first-hop router in the ANET for connecting MNs to
correspondents in outside Internetworks.
ANET interface
a MN'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 MNs and INET
correspondents. Examples include private enterprise networks,
ground domain aviation service networks and the global public
Internet itself.
INET interface
a node's attachment to a link in an INET.
OMNI link
a virtual overlay configured over one or more INETs and their
connected ANETs. An OMNI link can comprise multiple INET 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.
OMNI interface
a node's attachment to an OMNI link, and configured over one or
more underlying ANET/INET interfaces.
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OMNI link local address (LLA)
an IPv6 link-local address constructed as specified in Section 7,
and assigned to an OMNI interface.
OMNI Option
an IPv6 Neighbor Discovery option providing multilink parameters
for the OMNI interface as specified in Section 9.
Multilink
an OMNI interface's manner of managing diverse underlying data
link interfaces as a single logical unit. The OMNI interface
provides a single unified interface to upper layers, while
underlying data link selections are performed on a per-packet
basis considering factors such as DSCP, flow label, application
policy, signal quality, cost, etc. Multilinking decisions are
coordinated in both the outbound (i.e. MN to correspondent) and
inbound (i.e., correspondent to MN) directions.
L2
The second layer in the OSI network model. Also known as "layer-
2", "link-layer", "sub-IP layer", "data link layer", etc.
L3
The third layer in the OSI network model. Also known as "layer-
3", "network-layer", "IPv6 layer", etc.
underlying interface
an ANET/INET interface over which an OMNI interface is configured.
The OMNI interface is seen as a L3 interface by the IP layer, and
each underlying interface is seen as a L2 interface by the OMNI
interface.
Mobility Service Identification (MSID)
Each MSE and AR is assigned a unique 32-bit Identification (MSID)
as specified in Section 7.
Safety-Based Multilink (SBM)
A means for ensuring fault tolerance through redundancy by
connecting multiple independent OMNI interfaces to independent
routing topologies (i.e., multiple independent OMNI links).
Performance Based Multilink (PBM)
A means for selecting underlying interface(s) for packet
trasnmission and reception within a single OMNI interface.
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3. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
An implementation is not required to internally use the architectural
constructs described here so long as its external behavior is
consistent with that described in this document.
4. Overlay Multilink Network (OMNI) Interface Model
An OMNI interface is a MN virtual interface configured over one or
more underlying interfaces, which may be physical (e.g., an
aeronautical radio link) or virtual (e.g., an Internet or higher-
layer "tunnel"). The MN receives a MNP from the MS, and coordinates
with the MS through IPv6 ND message exchanges. The MN uses the MNP
to construct a unique OMNI LLA through the algorithmic derivation
specified in Section 7 and assigns the LLA to the OMNI interface.
The OMNI interface architectural layering model is the same as in
[RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer
therefore sees the OMNI interface as a single L3 interface with
multiple underlying interfaces that appear as L2 communication
channels in the architecture.
+----------------------------+
| Upper Layer Protocol |
Session-to-IP +---->| |
Address Binding | +----------------------------+
+---->| IP (L3) |
IP Address +---->| |
Binding | +----------------------------+
+---->| OMNI Interface |
Logical-to- +---->| (OMNI LLA) |
Physical | +----------------------------+
Interface +---->| L2 | L2 | | L2 |
Binding |(IF#1)|(IF#2)| ..... |(IF#n)|
+------+------+ +------+
| L1 | L1 | | L1 |
| | | | |
+------+------+ +------+
Figure 1: OMNI Interface Architectural Layering Model
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The OMNI virtual interface model gives rise to a number of
opportunities:
o since OMNI LLAs are uniquely derived from an MNP, no Duplicate
Address Detection (DAD) or Muticast Listener Discovery (MLD)
messaging is necessary.
o ANET interfaces do not require any L3 addresses (i.e., not even
link-local) in environments where communications are coordinated
entirely over the OMNI interface. (An alternative would be to
also assign the same OMNI LLA to all ANET interfaces.)
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 multilink operation (including QoS based link
selection, packet replication, load balancing, etc.) at L2 while
still permitting L3 traffic shaping based on, e.g., DSCP, flow
label, etc.
o L3 sees the OMNI interface as a point of connection to the OMNI
link; if there are multiple OMNI links (i.e., multiple MS's), L3
will see multiple OMNI interfaces.
o Multiple independent OMNI interfaces can be used for increased
fault tolerance through Safety-Based Multilink (SBM), with
Performance-Based Multilink (PBM) applied within each interface.
Other opportunities are discussed in [RFC7847].
Figure 2 depicts the architectural model for a MN connecting to the
MS via multiple independent ANETs. When an underlying interface
becomes active, the MN's OMNI interface sends native (i.e.,
unencapsulated) IPv6 ND messages via the underlying interface. IPv6
ND messages traverse the ground domain ANETs until they reach an
Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a
Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and
returns an IPv6 ND message response to the MN. IPv6 ND messages
traverse the ANET at layer 2; hence, the Hop Limit is not
decremented.
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+--------------+
| MN |
+--------------+
|OMNI interface|
+----+----+----+
+--------|IF#1|IF#2|IF#n|------ +
/ +----+----+----+ \
/ | \
/ <---- Native | IP ----> \
v v v
(:::)-. (:::)-. (:::)-.
.-(::ANET:::) .-(::ANET:::) .-(::ANET:::)
`-(::::)-' `-(::::)-' `-(::::)-'
+----+ +----+ +----+
... |AR#1| .......... |AR#2| ......... |AR#n| ...
. +-|--+ +-|--+ +-|--+ .
. | | |
. v v v .
. <----- Encapsulation -----> .
. .
. +-----+ (:::)-. .
. |MSE#2| .-(::::::::) +-----+ .
. +-----+ .-(::: INET :::)-. |MSE#m| .
. (::::: Routing ::::) +-----+ .
. `-(::: System :::)-' .
. +-----+ `-(:::::::-' .
. |MSE#1| +-----+ +-----+ .
. +-----+ |MSE#3| |MSE#4| .
. +-----+ +-----+ .
. .
. .
. <----- Worldwide Connected Internetwork ----> .
...........................................................
Figure 2: MN/MS Coordination via Multiple ANETs
After the initial IPv6 ND message exchange, the MN can send and
receive unencapsulated IPv6 data packets over the OMNI interface.
OMNI interface multilink services will forward the packets via ARs in
the correct underlying ANETs. The AR encapsulates the packets
according to the capabilities provided by the MS and forwards them to
the next hop within the worldwide connected Internetwork via optimal
routes.
OMNI links span one or more underlying Internetwork via a mid-layer
overlay encapsulation based on [RFC2473] and using [RFC4193]
addressing. Each OMNI link corresponds to a different overlay
(differentiated by an address codepoint) which may be carried over a
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completely separate underlying topology. Each MN can facilitate SBM
by connecting to multiple OMNI links using a distinct OMNI interface
for each link.
5. Maximum Transmission Unit (MTU) and Fragmentation
The OMNI interface observes the link nature of tunnels, including the
Maximum Transmission Unit (MTU) and the role of fragmentation and
reassembly[I-D.ietf-intarea-tunnels]. The OMNI interface is
configured over one or more underlying interfaces that may have
diverse MTUs.
IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of
1280 bytes [RFC8200]. The network therefore MUST forward packets of
at least 1280 bytes without generating an IPv6 Path MTU Discovery
(PMTUD) Packet Too Big (PTB) message [RFC8201]. The minimum MTU for
IPv4 underlying interfaces is only 68 bytes [RFC1122], meaning that a
packet smaller than the IPv6 minimum MTU may require fragmentation
when IPv4 encapsulation is used. Therefore, the Don't Fragment (DF)
bit in the IPv4 encapsulation header MUST be set to 0
The OMNI interface configures an MTU of 9180 bytes [RFC2492]; the
size is therefore not a reflection of the underlying interface MTUs,
but rather determines the largest packet the OMNI interface can
forward or reassemble. The OMNI interface therefore accommodates
packets as large as the OMNI interface MTU while generating IPv6 Path
MTU Discovery (PMTUD) Packet Too Big (PTB) messages [RFC8201] as
necessary (see below). For IPv4 packets with DF=0, the IP layer
performs IPv4 fragmentation if necessary to admit the fragments into
the OMNI interface. The interface may then internally apply further
IPv4 fragmentation prior to encapsulation to ensure that the IPv4
fragments are delivered to the final destination.
OMNI interfaces internally employ OMNI link encapsulation and
fragmentation/reassembly per [RFC2473]. The encapsulation inserts a
mid-layer IPv6 header between the inner IP packet and any outer IP
encapsulation headers. The OMNI interface returns internally-
generated PTB messages for packets admitted into the interface that
it deems too large (e.g., according to link performance
characteristics, reassembly cost, etc.) while either dropping or
forwarding the packet as necessary. The OMNI interface performs
PMTUD even if the destination appears to be on the same link since an
OMNI link node on the path may return a PTB. This ensures that the
path MTU is adaptive and reflects the current path used for a given
data flow.
OMNI interfaces perform encapsulation and fragmentation/reassembly as
follows:
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o When an OMNI interface sends a packet toward a final destination
via an ANET peer, it sends without OMNI link encapsulation if the
packet is no larger than the underlying interface MTU. Otherwise,
it inserts an IPv6 header with source address set to the node's
own OMNI Unique Local Address (ULA) (see: Section 8) and
destination set to the OMNI ULA of the ANET peer. The OMNI
interface then uses IPv6 fragmentation to break the packet into a
minimum number of non-overlapping fragments, where the largest
fragment size is determined by the underlying interface MTU and
the smallest fragment is no smaller than 640 bytes. The OMNI
interface then sends the fragments to the ANET peer, which
reassembles before forwarding toward the final destination.
o When an OMNI interface sends a packet toward a final destination
via an INET interface, it sends packets no larger than 1280 bytes
(including any INET encapsulation headers) without inserting a
mid-layer IPv6 header if the destination is reached via an INET
address within the same OMNI link segment. Otherwise, it inserts
an IPv6 header with source address set to the node's OMNI ULA,
destination set to the ULA of the next hop OMNI node toward the
final destination and (if necessary) with a Segment Routing Header
with the remaining Segment IDs on the path to the final
destination. The OMNI interface then uses IPv6 fragmentation to
break the encapsulated packet into a minimum number of non-
overlapping fragments, where the largest fragment size (including
both the OMNI mid-layer IPv6 and outer-layer INET encapsulations)
is 1280 bytes and the smallest fragment is no smaller than 640
bytes. The OMNI interface then encapsulates the fragments in any
INET headers and sends them to the OMNI link neighbor, which
reassembles before forwarding toward the final destination.
OMNI interfaces unconditionally drop all OMNI link fragments smaller
than 640 bytes. In order to set the correct context for reassembly,
the OMNI interface that inserts the IPv6 header MUST also be the one
that inserts the IPv6 Fragment Header Identification value. While
not strictly required, sending all fragments of the same fragmented
mid-layer packet consecutively over the same underlying interface
with minimal inter-fragment delay can in some cases increase the
likelihood of successful reassembly.
Note that the OMNI interface can forward large packets via
encapsulation and fragmentation while at the same time returning
"advisory" PTB messages (subject to rate limiting). The receiving
node that performs reassembly can also send advisory PTB messages if
reassembly conditions become unfavorable. The OMNI interface can
therefore continuously forward large packets without loss while
returning advisory PTB messages recommending a smaller size.
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OMNI interfaces that send advisory PTB messages set the ICMPv6
message header Code field to the value 1. Receiving nodes that
recognize the code reduce their estimate of the path MTU the same as
for ordinary "diagnistic" PTBs but do not regard the message as a
loss indication. Nodes that do not recognize the code treat the
message the same as a diagnostic PTB, but should heed the advice in
[RFC8201] regarding retransmissions. This document therefore updates
[RFC4443] and [RFC8201].
5.1. Fragmentation Security Implications
As discussed in Section 3.7 of [I-D.ietf-intarea-frag-fragile], there
are four basic threats concerning IPv6 fragmentation; each of which
is addressed by a suitable mitigation as follows:
1. Overlapping fragment attacks - reassembly of overlapping
fragments is forbidden by [RFC8200]; therefore, this threat does
not apply to OMNI interfaces.
2. Resource exhaustion attacks - this threat is mitigated by
providing a sufficiently large OMNI interface reassembly cache
and instituting "fast discard" of incomplete reassemblies that
may be part of a buffer exhaustion attack. The reassembly cache
should be sufficiently large so that a sustained attack does not
cause excessive loss of good reassemblies but not so large that
(timer-based) data structure management becomes computationally
expensive.
3. Attacks based on predictable fragment identification values -
this threat is mitigated by selecting a suitably random ID value
per [RFC7739].
4. Evasion of Network Intrusion Detection Systems (NIDS) - this
threat is mitigated by disallowing "tiny fragments" per the OMNI
interface fragmentation procedures specified above.
Additionally, IPv4 fragmentation includes a 16-bit Identification (IP
ID) field with only 65535 unique values, meaning that for even
moderately high data rates the field could wrap and apply to new
packets while the fragments of old packets using the same ID are
still alive in the network [RFC4963]. Since IPv6 provides a 32-bit
Identification value, however, this is not a concern for IPv6
fragmentation.
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6. Frame Format
The OMNI interface transmits IPv6 packets according to the native
frame format of each underlying 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 specified in
[RFC2473], etc.
7. Link-Local Addresses (LLAs)
OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI
LLAs") as follows:
o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP
within the least-significant 112 bits of the IPv6 link-local
prefix fe80::/16. For example, for the MNP
2001:db8:1000:2000::/56 the corresponding LLA is
fe80:2001:db8:1000:2000::. This updates the IPv6 link-local
address format specified in Section 2.5.6 of [RFC4291] by defining
a use for bits 11 - 63.
o IPv4-compatible MN OMNI LLAs are constructed as
fe80::ffff:[v4addr], i.e., the most significant 16 bits of the
prefix fe80::/16, followed by 64 '0' bits, followed by 16 '1'
bits, followed by a 32bit IPv4 address. For example, the
IPv4-Compatible MN OMNI LLA for 192.0.2.1 is fe80::ffff:192.0.2.1
(also written as fe80::ffff:c000:0201).
o MS OMNI LLAs are assigned to ARs and MSEs from the range
fe80::/96, and MUST be managed for uniqueness. The lower 32 bits
of the LLA includes a unique integer "MSID" value between
0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3,
etc., fe80::feff:ffff. The MSID 0x00000000 corresponds to the
link-local Subnet-Router anycast address (fe80::) [RFC4291]. The
MSID range 0xff000000 through 0xffffffff is reserved for future
use.
o The OMNI LLA range fe80::/32 is used as the service prefix for the
address format specified in Section 4 of [RFC4380] (see Section 17
for further discussion).
Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no
MNPs can be allocated from that block ensuring that there is no
possibility for overlap between the above OMNI LLA constructs.
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Since MN OMNI LLAs are based on the distribution of administratively
assured unique MNPs, and since MS OMNI LLAs are guaranteed unique
through administrative assignment, OMNI interfaces set the
autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862].
8. Unique-Local Addresses (ULAs)
OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs")
[RFC4193] as the source and destination addresses in OMNI link IPv6
encapsulation headers. This document updates [RFC4193] by reserving
the ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs.
Each OMNI link instance is identified by bits 10-15 of the OMNI
service prefix fc80::/10. For example, OMNI ULAs associated with
instance 0 are configured from the prefix fc80::/16, instance 1 from
fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs are
configured in one-to-one correspondence with OMNI LLAs through
stateless prefix translation. For example, for OMNI link instance
fc80::/16:
o the OMNI ULA corresponding to fe80:2001:db8:1:2:: is simply
fc80:2001:db8:1:2::
o the OMNI ULA corresponding to fe80::ffff:192.0.2.1 is simply
fc80::ffff:192.0.2.1
o the OMNI ULA corresponding to fe80::1000 is simply fc80::1000
o the OMNI ULA corresponding to fe80:: is simply fc80::
Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI
link instance, e.g., the OMNI interface connected to instance 3
assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI
interfaces advertise the OMNI service prefix (e.g., fc83::/16) into
the local routing system so that applications can direct traffic
according to SBM requirements.
The OMNI ULA presents an IPv6 address format that is routable within
the OMNI link routing system and can be used to convey link-scoped
messages across multiple hops using IPv6 encapsulation [RFC2473].
The OMNI link extends across one or more underling Internetworks to
include all ARs and MSEs. All MNs are also considered to be
connected to the OMNI link, however OMNI link encapsulation is
omitted over ANET links when possible to conserve bandwidth (see:
Section 11).
The OMNI link can be subdivided into "segments" that often correspond
to different administrative domains or physical partitions. OMNI
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nodes can use IPv6 Segment Routing [RFC8402] when necessary to
support efficient packet forwarding to destinations located in other
OMNI link segments. A full discussion of Segment Routing over the
OMNI link appears in [I-D.templin-intarea-6706bis].
9. Address Mapping - Unicast
OMNI interfaces maintain a neighbor cache for tracking per-neighbor
state and use the link-local address format specified in Section 7.
IPv6 Neighbor Discovery (ND) [RFC4861] messages on MN OMNI interfaces
observe the native Source/Target Link-Layer Address Option (S/TLLAO)
formats of the underlying 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 OMNI interface would therefore appear to have multiple L2
connections, and may include information for multiple underlying
interfaces in a single IPv6 ND message exchange.
OMNI interfaces use an IPv6 ND option called the "OMNI option"
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 | Prefix Length |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Sub-Options ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: OMNI Option Format
In this format:
o Type is set to TBD.
o Length is set to the number of 8 octet blocks in the option.
o Prefix Length is set according to the IPv6 source address type.
For MN OMNI LLAs, the value is set to the length of the embedded
MNP. For IPv4-compatible MN OMNI LLAs, the value is set to 96
plus the length of the embedded IPv4 prefix. For MS OMNI LLAs,
the value is set to 128.
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o R (the "Register/Release" bit) is set to 1/0 to request the
message recipient to register/release a MN's MNP. The OMNI option
may additionally include MSIDs for the recipient to contact to
also register/release the MNP.
o Reserved is set to the value '0' on transmission and ignored on
reception.
o Sub-Options is a Variable-length field, of length such that the
complete OMNI Option is an integer multiple of 8 octets long.
Contains one or more options, as described in Section 9.1.
9.1. Sub-Options
The OMNI option includes zero or more Sub-Options, some of which may
appear multiple times in the same message. Each consecutive Sub-
Option is concatenated immediately after its predecessor. All Sub-
Options except Pad1 (see below) are type-length-value (TLV) encoded
in the following format:
0 1 2
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Sub-Type | Sub-length | Sub-Option Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 4: Sub-Option Format
o Sub-Type is a 1-byte field that encodes the Sub-Option type. Sub-
Options defined in this document are:
Option Name Sub-Type
Pad1 0
PadN 1
ifIndex-tuple (Type 1) 2
ifIndex-tuple (Type 2) 3
MS-Register 4
MS-Release 5
Network Access Identifier 6
Geo Coordinates 7
Figure 5
Sub-Types 253 and 254 are reserved for experimentation, as
recommended in [RFC3692].
o Sub-Length is a 1-byte field that encodes the length of the Sub-
Option Data, in bytes
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o Sub-Option Data is a byte string with format determined by Sub-
Type
During processing, unrecognized Sub-Options are ignored and the next
Sub-Option processed until the end of the OMNI option.
The following Sub-Option types and formats are defined in this
document:
9.1.1. Pad1
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Sub-Type=0 |
+-+-+-+-+-+-+-+-+
Figure 6: Pad1
o Sub-Type is set to 0.
o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option"
consists of a single zero octet).
9.1.2. PadN
0 1 2
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Sub-Type=1 |Sub-length=N-2 | N-2 padding bytes ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 7: PadN
o Sub-Type is set to 1.
o Sub-Length is set to N-2 being the number of padding bytes that
follow.
o Sub-Option Data consists of N-2 zero-valued octets.
9.1.3. ifIndex-tuple (Type 1)
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=2 | Sub-length=4+N| ifIndex | ifType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link |S|I|RSV| Bitmap(0)=0xff|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| Bitmap(1)=0xff|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P32|P33|P34|P35|P36|P37|P38|P39| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 8: ifIndex-tuple (Type 1)
o Sub-Type is set to 2.
o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that
follow).
o Sub-Option Data contains an "ifIndex-tuple" (Type 1) encoded as
follows (note that the first four bytes must be present):
* ifIndex is set to an 8-bit integer value corresponding to a
specific underlying interface. OMNI options MAY include
multiple ifIndex-tuples, and MUST number each with an ifIndex
value between '1' and '255' that represents a MN-specific 8-bit
mapping for the actual ifIndex value assigned to the underlying
interface by network management [RFC2863] (the ifIndex value
'0' is reserved for use by the MS). Multiple ifIndex-tuples
with the same ifIndex value MAY appear in the same OMNI option.
* ifType is set to an 8-bit integer value corresponding to the
underlying interface identified by ifIndex. The value
represents an OMNI interface-specific 8-bit mapping for the
actual IANA ifType value registered in the 'IANAifType-MIB'
registry [http://www.iana.org].
* Provider ID is set to an OMNI interface-specific 8-bit ID value
for the network service provider associated with this ifIndex.
* Link encodes a 4-bit link metric. The value '0' means the link
is DOWN, and the remaining values mean the link is UP with
metric ranging from '1' ("lowest") to '15' ("highest").
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* S is set to '1' if this ifIndex-tuple corresponds to the
underlying interface that is the source of the ND message. Set
to '0' otherwise.
* I is set to '0' ("Simplex") if the index for each singleton
Bitmap byte in the Sub-Option Data is inferred from its
sequential position (i.e., 0, 1, 2, ...), or set to '1'
("Indexed") if each Bitmap is preceded by an Index byte.
Figure 8 shows the simplex case for I set to '0'. For I set to
'1', each Bitmap is instead preceded by an Index byte that
encodes a value "i" = (0 - 255) as the index for its companion
Bitmap as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Index=i | Bitmap(i) |P[*] values ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 9
* RSV is set to the value 0 on transmission and ignored on
reception.
* The remainder of the Sub-Option Data contains N = (0 - 251)
bytes of traffic classifier preferences consisting of a first
(indexed) Bitmap (i.e., "Bitmap(i)") followed by 0-8 1-byte
blocks of 2-bit P[*] values, followed by a second Bitmap (i),
followed by 0-8 blocks of P[*] values, etc. Reading from bit 0
to bit 7, the bits of each Bitmap(i) that are set to '1''
indicate the P[*] blocks from the range P[(i*32)] through
P[(i*32) + 31] that follow; if any Bitmap(i) bits are '0', then
the corresponding P[*] block is instead omitted. For example,
if Bitmap(0) contains 0xff then the block with P[00]-P[03],
followed by the block with P[04]-P[07], etc., and ending with
the block with P[28]-P[31] are included (as shown in Figure 8).
The next Bitmap(i) is then consulted with its bits indicating
which P[*] blocks follow, etc. out to the end of the Sub-
Option. The first 16 P[*] blocks correspond to the 64
Differentiated Service Code Point (DSCP) values P[00] - P[63]
[RFC2474]. Any additional P[*] blocks that follow correspond
to "pseudo-DSCP" traffic classifier values P[64], P[65], P[66],
etc. See Appendix A for further discussion and examples.
* Each 2-bit P[*] field is set to the value '0' ("disabled"), '1'
("low"), '2' ("medium") or '3' ("high") to indicate a QoS
preference level for underlying interface selection purposes.
Not all P[*] values need to be included in all OMNI option
instances of a given ifIndex-tuple. Any P[*] values
represented in an earlier OMNI option but omitted in the
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current OMNI option remain unchanged. Any P[*] values not yet
represented in any OMNI option default to "medium".
9.1.4. ifIndex-tuple (Type 2)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=3 | Sub-length=4+N| ifIndex | ifType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link |S|Resvd| ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ ~
~ RFC 6088 Format Traffic Selector ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: ifIndex-tuple (Type 2)
o Sub-Type is set to 3.
o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that
follow).
o Sub-Option Data contains an "ifIndex-tuple" (Type 2) encoded as
follows (note that the first four bytes must be present):
* ifIndex, ifType, Provider ID, Link and S are set exactly as for
Type 1 ifIndex-tuples as specified in Section 9.1.3.
* the remainder of the Sub-Option body encodes a variable-length
traffic selector formatted per [RFC6088], beginning with the
"TS Format" field.
9.1.5. MS-Register
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=4 | Sub-length=4 | MSID (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID (bits 16 - 32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: MS-Register Sub-option
o Sub-Type is set to 4.
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o Sub-Length is set to 4.
o MSID contains the 32 bit ID of an MSE or AR, in network byte
order. OMNI options contain zero or more MS-Register sub-options.
9.1.6. MS-Release
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=5 | Sub-length=4 | MSID (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID (bits 16 - 32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: MS-Release Sub-option
o Sub-Type is set to 5.
o Sub-Length is set to 4.
o MSIID contains the 32 bit ID of an MS or AR, in network byte
order. OMNI options contain zero or more MS-Release sub-options.
9.1.7. Network Access Identifier (NAI)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 13: Network Access Identifier (NAI) Sub-option
o Sub-Type is set to 6.
o Sub-Length is set to N.
o Network Access Identifier (NAI) is coded per [RFC7542], and is up
to 253 bytes in length.
9.1.8. Geo Coordiantes
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=7 | Sub-length=N | Geo Coordinates
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 14: Geo Coordinates Sub-option
o Sub-Type is set to 7.
o Sub-Length is set to N.
o A set of Geo Coordinates up to 253 bytes in length (format TBD).
Includes Latitude/Longitude at a minimum; may also include
additional attributes such as altitude, heading, speed, etc.).
10. Address Mapping - Multicast
The multicast address mapping of the native underlying interface
applies. The mobile router on board the MN also serves as an IGMP/
MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while
using the L2 address of the AR as the L2 address for all multicast
packets.
The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to
coordinate with the AR, and ANET L2 elements use MLD snooping
[RFC4541].
11. Conceptual Sending Algorithm
The MN's IPv6 layer selects the outbound OMNI interface according to
SBM considerations when forwarding data packets from local or EUN
applications to external correspondents. Each OMNI interface
maintains a neighbor cache the same as for any IPv6 interface, but
with additional state for multilink coordination.
After a packet enters the OMNI interface, an outbound underlying
interface is selected based on PBM traffic selectors such as DSCP,
application port number, cost, performance, message size, etc. OMNI
interface multilink selections could also be configured to perform
replication across multiple underlying interfaces for increased
reliability at the expense of packet duplication.
When an OMNI interface sends a packet over a selected outbound
underlying interface, it omits OMNI link encapsulation if the packet
does not require fragmentation and the neighbor can determine the
OMNI ULAs through other means (e.g., the packet's destination,
neighbor cache information, etc.). Otherwise, the OMNI interface
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inserts an IPv6 header with the OMNI ULAs and performs fragmentation
if necessary. The OMNI interface also performs enacpsulation when
the nearest AR is located multiple hops away as discussed in
Section 12.1.
OMNI interface multilink service designers MUST observe the BCP
guidance in Section 15 [RFC3819] in terms of implications for
reordering when packets from the same flow may be spread across
multiple underlying interfaces having diverse properties.
11.1. Multiple OMNI Interfaces
MNs may connect to multiple independent OMNI links concurrently in
support of SBM. Each OMNI interface is distinguished by its Anycast
OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a
separate OMNI interface for each link so that multiple interfaces
(e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A
different Anycast OMNI ULA is assigned to each interface, and the MN
injects the service prefixes for the OMNI link instances into the EUN
routing system.
Applications in EUNs can use Segment Routing to select the desired
OMNI interface based on SBM considerations. The Anycast OMNI ULA is
written into the IPv6 destination address, and the actual destination
(along with any additional intermediate hops) is written into the
Segment Routing Header. Standard IP routing directs the packets to
the MN's mobile router entity, and the Anycast OMNI ULA identifies
the OMNI interface to be used for transmission to the next hop. When
the MN receives the message, it replaces the IPv6 destination address
with the next hop found in the routing header and transmits the
message over the OMNI interface identified by the Anycast OMNI ULA.
Multiple distinct OMNI links can therefore be used to support fault
tolerance, load balancing, reliability, etc. The architectural model
is similar to Layer 2 Virtual Local Area Networks (VLANs).
12. Router Discovery and Prefix Registration
MNs interface with the MS by sending RS messages with OMNI options
under the assumption that a single AR on the ANET will process the
message and respond. This places a requirement on each ANET, which
may be enforced by physical/logical partitioning, L2 AR beaconing,
etc. The manner in which the ANET ensures single AR coordination is
link-specific and outside the scope of this document.
For each underlying interface, the MN sends an RS message with an
OMNI option with prefix registration information, ifIndex-tuples, MS-
Register/Release suboptions containing MSIDs, and with destination
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address set to link-scoped All-Routers multicast (ff02::2) [RFC4291].
Example MSID discovery methods are given in [RFC5214], including data
link login parameters, name service lookups, static configuration,
etc. Alternatively, MNs can discover individual MSIDs by sending an
initial RS with MS-Register MSID set to 0x00000000.
MNs configure OMNI interfaces that observe the properties discussed
in the previous section. The OMNI 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 OMNI 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 OMNI interface also transitions to UP. When all
underlying interfaces transition to DOWN, the OMNI interface also
transitions to DOWN.
When an OMNI interface transitions to UP, the MN sends RS messages to
register its MNP and an initial set of underlying interfaces that are
also UP. The MN sends additional RS messages to refresh lifetimes
and to register/deregister underlying interfaces as they transition
to UP or DOWN. The MN sends initial RS messages over an UP
underlying interface with its OMNI LLA as the source and with
destination set to All-Routers multicast. The RS messages include an
OMNI option per Section 9 with valid prefix registration information,
ifIndex-tuples appropriate for underlying interfaces and MS-Register/
Release sub-options.
ARs process IPv6 ND messages with OMNI options and act as a proxy for
MSEs. ARs receive RS messages and create a neighbor cache entry for
the MN, then coordinate with any named MSIDs in a manner outside the
scope of this document. The AR returns an RA message with
destination address set to the MN OMNI LLA (i.e., unicast), with
source address set to its MS OMNI LLA, with the P(roxy) bit set in
the RA flags [RFC4389][RFC5175], with an OMNI option with valid
prefix registration information, ifIndex-tuples, MS-Register/Release
sub-options, and with any information for the link that would
normally be delivered in a solicited RA message. ARs return RA
messages with configuration information in response to a MN's RS
messages. The AR sets the RA Cur Hop Limit, M and O flags, Router
Lifetime, Reachable Time and Retrans Timer values, and includes any
necessary options such as:
o PIOs with (A; L=0) that include MSPs for the link [RFC8028].
o RIOs [RFC4191] with more-specific routes.
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o an MTU option that specifies the maximum acceptable packet size
for this ANET interface.
The AR coordinates with each Register/Release MSID then sends an
immediate unicast RA response without delay; therefore, the IPv6 ND
MAX_RA_DELAY_TIME and MIN_DELAY_BETWEEN_RAS constants for multicast
RAs do not apply. The AR MAY send periodic and/or event-driven
unsolicited RA messages according to the standard [RFC4861].
When the MSE processes the OMNI information, it first validates the
prefix registration information. The MSE then injects/withdraws the
MNP in the routing/mapping system and caches/discards the new Prefix
Length, MNP and ifIndex-tuples. The MSE then informs the AR of
registration success/failure, and the AR adds the MSE to the list of
Register/Release MSIDs to return in an RA message OMNI option per
Section 9.
When the MN receives the RA message, it creates an OMNI interface
neighbor cache entry with the AR's address as an L2 address and
records the MSIDs that have confirmed MNP registration via this AR.
If the MN connects to multiple ANETs, it establishes additional AR L2
addresses (i.e., as a Multilink neighbor). The MN then manages its
underlying interfaces according to their states as follows:
o When an underlying interface transitions to UP, the MN sends an RS
over the underlying interface with an OMNI option with R set to 1.
The OMNI option contains at least one ifIndex-tuple with values
specific to this underlying interface, and may contain additional
ifIndex-tuples specific to this and/or other underlying
interfaces. The option also includes any Register/Release MSIDs.
o When an underlying interface transitions to DOWN, the MN sends an
RS or unsolicited NA message over any UP underlying interface with
an OMNI option containing an ifIndex-tuple for the DOWN underlying
interface with Link set to '0'. The MN sends an RS when an
acknowledgement is required, or an unsolicited NA when reliability
is not thought to be a concern (e.g., if redundant transmissions
are sent on multiple underlying interfaces).
o When the Router Lifetime for a specific AR nears expiration, the
MN sends an RS over the underlying interface to receive a fresh
RA. If no RA is received, the MN marks the underlying interface
as DOWN.
o When a MN wishes to release from one or more current MSIDs, it
sends an RS or unsolicited NA message over any UP underlying
interfaces with an OMNI option with a Release MSID. Each MSID
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then withdraws the MNP from the routing/mapping system and informs
the AR that the release was successful.
o When all of a MNs underlying interfaces have transitioned to DOWN
(or if the prefix registration lifetime expires), any associated
MSEs withdraw the MNP the same as if they had received a message
with a release indication.
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 a an UP
underlying interface, the MN declares this underlying interface as
DOWN.
The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface.
Therefore, when the IPv6 layer sends an RS message the OMNI interface
returns an internally-generated RA message as though the message
originated from an IPv6 router. The internally-generated RA message
contains configuration information that is consistent with the
information received from the RAs generated by the MS. Whether the
OMNI 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 proactively.
Note: The Router Lifetime value in RA messages indicates the time
before which the MN must send another RS message over this underlying
interface (e.g., 600 seconds), however that timescale may be
significantly longer than the lifetime the MS has committed to retain
the prefix registration (e.g., REACHABLETIME seconds). ARs are
therefore responsible for keeping MS state alive on a shorter
timescale than the MN is required to do on its own behalf.
Note: On multicast-capable underlying interfaces, MNs should send
periodic unsolicited multicast NA messages and ARs should send
periodic unsolicited multicast RA messages as "beacons" that can be
heard by other nodes on the link. If a node fails to receive a
beacon after a timeout value specific to the link, it can initiate a
unicast exchange to test reachability.
12.1. Multihop Router Discovery
On some ANET types (e.g., omni-directional ad-hoc wireless) a MN may
be located multiple hops away from a node which has connectivity to
the nearest AR. Forwarding through these multiple hops would be
conducted through the application of a Mobile Ad-hoc Network (MANET)
routing protocol operating across the ANET interfaces.
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A MN located potentially multiple ANET hops away from the nearst AR
prepares an RS message as normal then encapsulates the message in an
IPv6 header with source address set to the ULA corresponding to the
RS LLA source address, and with destination set to site-scoped All-
Routers multicast (ff05::2)[RFC4291]. The MN then sends the
encapsulated RS message via the ANET interface, where it will be
received by zero or more nearby intermediate MNs.
When an intermediate MN that particpates in the MANET routing
protocol receives the encapsulated RS, it forwards the message
according to its (ULA-based) MANET routing tables. This process
repeats iteratively until the RS message is received by an ultimate
MN that is within communications range of an AR, which forwards the
message to the AR.
When the AR receives the RS message, it coordinates with the MS the
same as if the message were received as an ordinary link-local RS,
since the inner Hop Limit will not have been decremented by the MANET
multihop forwarding process. The AR then prepares an RA message with
source address set to its own LLA and destination address set to the
LLA of the original MN, then encapsulates the message in an IPv6
header with source and destination set to the ULAs corresponding to
the inner header.
The AR then forwards the message to an MN within communications
range, which forwards the message according to its MANET routing
tables to an intermediate MN. The MANET forwarding process continues
repetitively until the message is delivered to the original MN, which
decapsulates the message and performs autoconfiguration the same as
if it had received the RA directly from an AR.
Note: An alternate approach to encapsulation of IPv6 ND messages for
multihop forwarding would be to statelessly translate the IPv6 LLAs
into ULAs and forward the messages without encapsulation. This would
violate the [RFC4861] requirement that certain IPv6 ND messages must
use link-local addresses and must not be accepted if received with
Hop Limit less than 255. This document therefore advocates
encapsulation since the overhead is nominal considering the
infrequent nature and small size of IPv6 ND messages. Future
documents may consider encapsulation avoidance through translation
while updating [RFC4861].
13. Secure Redirection
If the ANET link model is multiple access, the AR is responsible for
assuring that address duplication cannot corrupt the neighbor caches
of other nodes on the link. When the MN sends an RS message on a
multiple access ANET link, the AR verifies that the MN is authorized
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to use the address and returns an RA with a non-zero Router Lifetime
only if the MN is authorized.
After verifying MN authorization and returning an RA, the AR MAY
return IPv6 ND Redirect messages to direct MNs located on the same
ANET link to exchange packets directly without transiting the AR. In
that case, the MNs can exchange packets according to their unicast L2
addresses discovered from the Redirect message instead of using the
dogleg path through the AR. In some ANET links, however, such direct
communications may be undesirable and continued use of the dogleg
path through the AR may provide better performance. In that case,
the AR can refrain from sending Redirects, and/or MNs can ignore
them.
14. AR and MSE Resilience
ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP)
[RFC5798] configurations so that service continuity is maintained
even if one or more ARs fail. Using VRRP, the MN is unaware which of
the (redundant) ARs is currently providing service, and any service
discontinuity will be limited to the failover time supported by VRRP.
Widely deployed public domain implementations of VRRP are available.
MSEs SHOULD use high availability clustering services so that
multiple redundant systems can provide coordinated response to
failures. As with VRRP, widely deployed public domain
implementations of high availability clustering services are
available. Note that special-purpose and expensive dedicated
hardware is not necessary, and public domain implementations can be
used even between lightweight virtual machines in cloud deployments.
15. Detecting and Responding to MSE Failures
In environments where fast recovery from MSE failure is required, ARs
SHOULD use proactive Neighbor Unreachability Detection (NUD) in a
manner that parallels Bidirectional Forwarding Detection (BFD)
[RFC5880] to track MSE reachability. ARs can then quickly detect and
react to failures so that cached information is re-established
through alternate paths. Proactive NUD control messaging is carried
only over well-connected ground domain networks (i.e., and not low-
end ANET links such as aeronautical radios) and can therefore be
tuned for rapid response.
ARs perform proactive NUD for MSEs for which there are currently
active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs
of the outage by sending multicast RA messages on the ANET interface.
The AR sends RA messages to MNs via the ANET interface with an OMNI
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option with a Release ID for the failed MSE, and with destination
address set to All-Nodes multicast (ff02::1) [RFC4291].
The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated
by small delays [RFC4861]. Any MNs on the ANET interface that have
been using the (now defunct) MSE will receive the RA messages and
associate with a new MSE.
16. Transition Considerations
When a MN connects to an ANET link for the first time, it sends an RS
message with an OMNI option. If the first hop AR recognizes the
option, it returns an RA with its MS OMNI LLA as the source, the MN
OMNI LLA as the destination, the P(roxy) bit set in the RA flags and
with an OMNI option included. The MN then engages the AR according
to the OMNI link model specified above. If the first hop AR is a
legacy IPv6 router, however, it instead returns an RA message with no
OMNI option and with a non-OMNI unicast source LLA as specified in
[RFC4861]. In that case, the MN engages the ANET according to the
legacy IPv6 link model and without the OMNI extensions specified in
this document.
If the ANET link model is multiple access, there must be assurance
that address duplication cannot corrupt the neighbor caches of other
nodes on the link. When the MN sends an RS message on a multiple
access ANET link with an OMNI LLA source address and an OMNI option,
ARs that recognize the option ensure that the MN is authorized to use
the address and return an RA with a non-zero Router Lifetime only if
the MN is authorized. ARs that do not recognize the option instead
return an RA that makes no statement about the MN's authorization to
use the source address. In that case, the MN should perform
Duplicate Address Detection to ensure that it does not interfere with
other nodes on the link.
An alternative approach for multiple access ANET links to ensure
isolation for MN / AR communications is through L2 address mappings
as discussed in Appendix C. This arrangement imparts a (virtual)
point-to-point link model over the (physical) multiple access link.
17. OMNI Interfaces on the Open Internet
OMNI interfaces configured over INET interfaces that connect to the
open Internet can apply symmetric security services such as VPNs or
establish a direct link through some other means. In environments
where an explicit VPN or direct link may be impractical, OMNI
interfaces can instead use Teredo UDP/IP encapsulation
[RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and
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Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] can
also be used if additional authentication is necessary.)
The IPv6 ND control plane messages used to establish neighbor cache
state must be authenticated while data plane messages are delivered
the same as for ordinary best-effort Internet traffic with basic
source address-based data origin verification. Data plane
communications via OMNI interfaces that connect over the open
Internet without an explicit VPN should therefore employ transport-
or higher-layer security to ensure integrity and/or confidentiality.
OMNI interfaces in the open Internet are often located behind Network
Address Translators (NATs). The OMNI interface accommodates NAT
traversal using UDP/IP encapsulation and the mechanisms discussed in
[RFC6081][RFC4380][I-D.templin-intarea-6706bis].
18. Time-Varying MNPs
In some use cases, it is desirable, beneficial and efficient for the
MN to receive a constant MNP that travels with the MN wherever it
moves. For example, this would allow air traffic controllers to
easily track aircraft, etc. In other cases, however (e.g.,
intelligent transportation systems), the MN may be willing to
sacrifice a modicum of efficiency in order to have time-varying MNPs
that can be changed every so often to defeat adversarial tracking.
Prefix delegation services such as those discussed in
[I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis]
allow OMNI MNs that desire time-varying MNPs to obtain short-lived
prefixes. In that case, the identity of the MN can be used as a
prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier
(DUID) [RFC8415]). The MN would then be obligated to renumber its
internal networks whenever its MNP (and therefore also its OMNI
address) changes. This should not present a challenge for MNs with
automated network renumbering services, however presents limits for
the durations of ongoing sessions that would prefer to use a constant
address.
19. IANA Considerations
The IANA is instructed to allocate an official Type number TBD from
the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI
option. Implementations set Type to 253 as an interim value
[RFC4727].
The IANA is instructed to assign a new Code value "1" in the "ICMPv6
Code Fields: Type 2 - Packet Too Big" registry. The registry should
read as follows:
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Code Name Reference
--- ---- ---------
0 Diagnostic Packet Too Big [RFC4443]
1 Advisory Packet Too Big [RFCXXXX]
Figure 15: OMNI Option Sub-Type Values
The IANA is instructed to allocate one Ethernet unicast address TBD2
(suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet
Address Block - Unicast Use".
The OMNI option also defines an 8-bit Sub-Type field, for which IANA
is instructed to create and maintain a new registry entitled "OMNI
option Sub-Type values". Initial values for the OMNI option Sub-Type
values registry are given below; future assignments are to be made
through Expert Review [RFC8126].
Value Sub-Type name Reference
----- ------------- ----------
0 Pad1 [RFCXXXX]
1 PadN [RFCXXXX]
2 ifIndex-tuple (Type 1) [RFCXXXX]
3 ifIndex-tuple (Type 2) [RFCXXXX]
4 MS-Register [RFCXXXX]
5 MS-Release [RFCXXXX]
6 Network Acceess Identifier [RFCXXXX]
7 Geo Coordinates [RFCXXXX]
8-252 Unassigned
253-254 Experimental [RFCXXXX]
255 Reserved [RFCXXXX]
Figure 16: OMNI Option Sub-Type Values
20. Security Considerations
Security considerations for IPv6 [RFC8200] and IPv6 Neighbor
Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD
include Nonce and Timestamp options [RFC3971] when transaction
confirmation and/or time synchronization is needed.
OMNI interfaces configured over secured ANET interfaces inherit the
physical and/or link-layer security properties of the connected
ANETs. OMNI interfaces configured over open INET interfaces can use
symmetric securing services such as VPNs or can by some other means
establish a direct link. When a VPN or direct link may be
impractical, however, an asymmetric security service such as SEcure
Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated
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Addresses (CGAs) [RFC3972] and/or the Teredo Authentication option
[RFC4380] may be necessary.
While the OMNI link protects control plane messaging as discussed
above, applications should still employ transport- or higher-layer
security services to protect the data plane.
Security considerations for specific access network interface types
are covered under the corresponding IP-over-(foo) specification
(e.g., [RFC2464], [RFC2492], etc.).
Security considerations for IPv6 fragmentation and reassembly are
discussed in Section 5.1.
21. Acknowledgements
The first version of this document was prepared per the consensus
decision at the 7th Conference of the International Civil Aviation
Organization (ICAO) Working Group-I Mobility Subgroup on March 22,
2019. Consensus to take the document forward to the IETF was reached
at the 9th Conference of the Mobility Subgroup on November 22, 2019.
Attendees and contributors included: Guray Acar, Danny Bharj,
Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo,
Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu
Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg
Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane
Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman,
Fryderyk Wrobel and Dongsong Zeng.
The following individuals are acknowledged for their useful comments:
Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric
Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized
for their many helpful ideas and suggestions.
This work is aligned with the NASA Safe Autonomous Systems Operation
(SASO) program under NASA contract number NNA16BD84C.
This work is aligned with the FAA as per the SE2025 contract number
DTFAWA-15-D-00030.
22. References
22.1. 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>.
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[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>.
[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971,
DOI 10.17487/RFC3971, March 2005,
<https://www.rfc-editor.org/info/rfc3971>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[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>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.
[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>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[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>.
[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>.
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[RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont,
"Traffic Selectors for Flow Bindings", RFC 6088,
DOI 10.17487/RFC6088, January 2011,
<https://www.rfc-editor.org/info/rfc6088>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
22.2. Informative References
[I-D.ietf-intarea-frag-fragile]
Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O.,
and F. Gont, "IP Fragmentation Considered Fragile", draft-
ietf-intarea-frag-fragile-17 (work in progress), September
2019.
[I-D.ietf-intarea-tunnels]
Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-10 (work in
progress), September 2019.
[I-D.templin-6man-dhcpv6-ndopt]
Templin, F., "A Unified Stateful/Stateless Configuration
Service for IPv6", draft-templin-6man-dhcpv6-ndopt-09
(work in progress), January 2020.
[I-D.templin-intarea-6706bis]
Templin, F., "Asymmetric Extended Route Optimization
(AERO)", draft-templin-intarea-6706bis-52 (work in
progress), May 2020.
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[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over
ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998,
<https://www.rfc-editor.org/info/rfc2225>.
[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>.
[RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM
Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999,
<https://www.rfc-editor.org/info/rfc2492>.
[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>.
[RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692,
DOI 10.17487/RFC3692, January 2004,
<https://www.rfc-editor.org/info/rfc3692>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/info/rfc3810>.
[RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D.,
Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
Wood, "Advice for Internet Subnetwork Designers", BCP 89,
RFC 3819, DOI 10.17487/RFC3819, July 2004,
<https://www.rfc-editor.org/info/rfc3819>.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380,
DOI 10.17487/RFC4380, February 2006,
<https://www.rfc-editor.org/info/rfc4380>.
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[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April
2006, <https://www.rfc-editor.org/info/rfc4389>.
[RFC4541] Christensen, M., Kimball, K., and F. Solensky,
"Considerations for Internet Group Management Protocol
(IGMP) and Multicast Listener Discovery (MLD) Snooping
Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006,
<https://www.rfc-editor.org/info/rfc4541>.
[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>.
[RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly
Errors at High Data Rates", RFC 4963,
DOI 10.17487/RFC4963, July 2007,
<https://www.rfc-editor.org/info/rfc4963>.
[RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router
Advertisement Flags Option", RFC 5175,
DOI 10.17487/RFC5175, March 2008,
<https://www.rfc-editor.org/info/rfc5175>.
[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>.
[RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)",
RFC 5558, DOI 10.17487/RFC5558, February 2010,
<https://www.rfc-editor.org/info/rfc5558>.
[RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP)
Version 3 for IPv4 and IPv6", RFC 5798,
DOI 10.17487/RFC5798, March 2010,
<https://www.rfc-editor.org/info/rfc5798>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
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[RFC6081] Thaler, D., "Teredo Extensions", RFC 6081,
DOI 10.17487/RFC6081, January 2011,
<https://www.rfc-editor.org/info/rfc6081>.
[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>.
[RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542,
DOI 10.17487/RFC7542, May 2015,
<https://www.rfc-editor.org/info/rfc7542>.
[RFC7739] Gont, F., "Security Implications of Predictable Fragment
Identification Values", RFC 7739, DOI 10.17487/RFC7739,
February 2016, <https://www.rfc-editor.org/info/rfc7739>.
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
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[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference Encoding
Adaptation of the OMNI option Type 1 ifIndex-tuple's traffic
classifier Bitmap to specific Internetworks such as the Aeronautical
Telecommunications Network with Internet Protocol Services (ATN/IPS)
may include link selection preferences based on other traffic
classifiers (e.g., transport port numbers, etc.) in addition to the
existing DSCP-based preferences. Nodes on specific Internetworks
maintain a map of traffic classifiers to additional P[*] preference
fields beyond the first 64. For example, TCP port 22 maps to P[67],
TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc.
Implementations use Simplex or Indexed encoding formats for P[*]
encoding in order to encode a given set of traffic classifiers in the
most efficient way. Some use cases may be more efficiently coded
using Simplex form, while others may be more efficient using Indexed.
Once a format is selected for preparation of a single ifIndex-tuple
the same format must be used for the entire Sub-Option. Different
Sub-Options may use different formats.
The following figures show coding examples for various Simplex and
Indexed formats:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=2 | Sub-length=4+N| ifIndex | ifType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link |S|0|RSV| Bitmap(0)=0xff|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| Bitmap(1)=0xff|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap(2)=0xff|P64|P65|P67|P68| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 17: Example 1: Dense Simplex Encoding
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=2 | Sub-length=4+N| ifIndex | ifType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link |S|0|RSV| Bitmap(0)=0x00| Bitmap(1)=0x0f|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Bitmap(10)=0x00| ...
+-+-+-+-+-+-+-+-+-+-+-
Figure 18: Example 2: Sparse Simplex Encoding
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=2 | Sub-length=4+N| ifIndex | ifType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link |S|1|RSV| Index = 0x00 | Bitmap = 0x80 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap = 0x01 |796|797|798|799| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 19: Example 3: Indexed Encoding
Appendix B. 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
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.
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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
observing different protocols. It is therefore highly desirable that
all ground stations observe a common language of RS/RA as specified
in this document.
Note that links of this nature may benefit from compression
techniques that reduce the bandwidth necessary for conveying the same
amount of data. The IETF lpwan working group is considering possible
alternatives: [https://datatracker.ietf.org/wg/lpwan/documents].
Appendix C. MN / AR Isolation Through L2 Address Mapping
Per [RFC4861], IPv6 ND messages may be sent to either a multicast or
unicast link-scoped IPv6 destination address. However, IPv6 ND
messaging should be coordinated between the MN and AR only without
invoking other nodes on the ANET. This implies that MN / AR control
messaging should be isolated and not overheard by other nodes on the
link.
To support MN / AR isolation on some ANET links, ARs can maintain an
OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible
ANETs, this specification reserves one Ethernet unicast address TBD2
(see: Section 19). For non-Ethernet statically-addressed ANETs,
MSADDR is reserved per the assigned numbers authority for the ANET
addressing space. For still other ANETs, MSADDR may be dynamically
discovered through other means, e.g., L2 beacons.
MNs map the L3 addresses of all IPv6 ND messages they send (i.e.,
both multicast and unicast) to MSADDR instead of to an ordinary
unicast or multicast L2 address. In this way, all of the MN's IPv6
ND messages will be received by ARs that are configured to accept
packets destined to MSADDR. Note that multiple ARs on the link could
be configured to accept packets destined to MSADDR, e.g., as a basis
for supporting redundancy.
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Therefore, ARs must accept and process packets destined to MSADDR,
while all other devices must not process packets destined to MSADDR.
This model has well-established operational experience in Proxy
Mobile IPv6 (PMIP) [RFC5213][RFC6543].
Appendix D. Change Log
<< RFC Editor - remove prior to publication >>
Differences from draft-templin-6man-omni-interface-20 to draft-
templin-6man-omni-interface-21:
o Safety-Based Multilink (SBM) and Performance-Based Multilink
(PBM).
Differences from draft-templin-6man-omni-interface-18 to draft-
templin-6man-omni-interface-19:
o SEND/CGA.
Differences from draft-templin-6man-omni-interface-17 to draft-
templin-6man-omni-interface-18:
o Teredo
Differences from draft-templin-6man-omni-interface-14 to draft-
templin-6man-omni-interface-15:
o Prefix length discussions removed.
Differences from draft-templin-6man-omni-interface-12 to draft-
templin-6man-omni-interface-13:
o Teredo
Differences from draft-templin-6man-omni-interface-11 to draft-
templin-6man-omni-interface-12:
o Major simplifications and clarifications on MTU and fragmentation.
o Document now updates RFC4443 and RFC8201.
Differences from draft-templin-6man-omni-interface-10 to draft-
templin-6man-omni-interface-11:
o Removed /64 assumption, resulting in new OMNI address format.
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Differences from draft-templin-6man-omni-interface-07 to draft-
templin-6man-omni-interface-08:
o OMNI MNs in the open Internet
Differences from draft-templin-6man-omni-interface-06 to draft-
templin-6man-omni-interface-07:
o Brought back L2 MSADDR mapping text for MN / AR isolation based on
L2 addressing.
o Expanded "Transition Considerations".
Differences from draft-templin-6man-omni-interface-05 to draft-
templin-6man-omni-interface-06:
o Brought back OMNI option "R" flag, and discussed its use.
Differences from draft-templin-6man-omni-interface-04 to draft-
templin-6man-omni-interface-05:
o Transition considerations, and overhaul of RS/RA addressing with
the inclusion of MSE addresses within the OMNI option instead of
as RS/RA addresses (developed under FAA SE2025 contract number
DTFAWA-15-D-00030).
Differences from draft-templin-6man-omni-interface-02 to draft-
templin-6man-omni-interface-03:
o Added "advisory PTB messages" under FAA SE2025 contract number
DTFAWA-15-D-00030.
Differences from draft-templin-6man-omni-interface-01 to draft-
templin-6man-omni-interface-02:
o Removed "Primary" flag and supporting text.
o Clarified that "Router Lifetime" applies to each ANET interface
independently, and that the union of all ANET interface Router
Lifetimes determines MSE lifetime.
Differences from draft-templin-6man-omni-interface-00 to draft-
templin-6man-omni-interface-01:
o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104
for future use (most likely as "pseudo-multicast").
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o Non-normative discussion of alternate OMNI LLA construction form
made possible if the 64-bit assumption were relaxed.
Differences from draft-templin-atn-aero-interface-21 to draft-
templin-6man-omni-interface-00:
o Minor clarification on Type-2 ifIndex-tuple encoding.
o Draft filename change (replaces draft-templin-atn-aero-interface).
Differences from draft-templin-atn-aero-interface-20 to draft-
templin-atn-aero-interface-21:
o OMNI option format
o MTU
Differences from draft-templin-atn-aero-interface-19 to draft-
templin-atn-aero-interface-20:
o MTU
Differences from draft-templin-atn-aero-interface-18 to draft-
templin-atn-aero-interface-19:
o MTU
Differences from draft-templin-atn-aero-interface-17 to draft-
templin-atn-aero-interface-18:
o MTU and RA configuration information updated.
Differences from draft-templin-atn-aero-interface-16 to draft-
templin-atn-aero-interface-17:
o New "Primary" flag in OMNI option.
Differences from draft-templin-atn-aero-interface-15 to draft-
templin-atn-aero-interface-16:
o New note on MSE OMNI LLA uniqueness assurance.
o General cleanup.
Differences from draft-templin-atn-aero-interface-14 to draft-
templin-atn-aero-interface-15:
o General cleanup.
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Differences from draft-templin-atn-aero-interface-13 to draft-
templin-atn-aero-interface-14:
o General cleanup.
Differences from draft-templin-atn-aero-interface-12 to draft-
templin-atn-aero-interface-13:
o Minor re-work on "Notify-MSE" (changed to Notification ID).
Differences from draft-templin-atn-aero-interface-11 to draft-
templin-atn-aero-interface-12:
o Removed "Request/Response" OMNI option formats. Now, there is
only one OMNI option format that applies to all ND messages.
o Added new OMNI option field and supporting text for "Notify-MSE".
Differences from draft-templin-atn-aero-interface-10 to draft-
templin-atn-aero-interface-11:
o Changed name from "aero" to "OMNI"
o Resolved AD review comments from Eric Vyncke (posted to atn list)
Differences from draft-templin-atn-aero-interface-09 to draft-
templin-atn-aero-interface-10:
o Renamed ARO option to AERO option
o Re-worked Section 13 text to discuss proactive NUD.
Differences from draft-templin-atn-aero-interface-08 to draft-
templin-atn-aero-interface-09:
o Version and reference update
Differences from draft-templin-atn-aero-interface-07 to draft-
templin-atn-aero-interface-08:
o Removed "Classic" and "MS-enabled" link model discussion
o Added new figure for MN/AR/MSE model.
o New Section on "Detecting and responding to MSE failure".
Differences from draft-templin-atn-aero-interface-06 to draft-
templin-atn-aero-interface-07:
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o Removed "nonce" field from AR option format. Applications that
require a nonce can include a standard nonce option if they want
to.
o Various editorial cleanups.
Differences from draft-templin-atn-aero-interface-05 to draft-
templin-atn-aero-interface-06:
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
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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
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
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Fred L. Templin (editor)
The Boeing Company
P.O. Box 3707
Seattle, WA 98124
USA
Email: fltemplin@acm.org
Tony Whyman
MWA Ltd c/o Inmarsat Global Ltd
99 City Road
London EC1Y 1AX
England
Email: tony.whyman@mccallumwhyman.com
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