Network Working Group F. Templin, Ed.
Internet-Draft The Boeing Company
Intended status: Standards Track A. Whyman
Expires: October 15, 2020 MWA Ltd c/o Inmarsat Global Ltd
April 13, 2020
Transmission of IPv6 Packets over Overlay Multilink Network (OMNI)
Interfaces
draft-templin-6man-omni-interface-14
Abstract
Mobile nodes (e.g., aircraft of various configurations, terrestrial
vehicles, seagoing vessels, mobile enterprise 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
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on October 15, 2020.
Copyright Notice
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document authors. All rights reserved.
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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 . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 6
5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 10
6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 11
7. Link-Local Addresses . . . . . . . . . . . . . . . . . . . . 11
8. The SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 13
9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 14
9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1.3. ifIndex-tuple (Type 1) . . . . . . . . . . . . . . . 16
9.1.4. ifIndex-tuple (Type 2) . . . . . . . . . . . . . . . 18
9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 19
9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 19
10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 20
11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 20
11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 20
12. Router Discovery and Prefix Registration . . . . . . . . . . 21
13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 24
14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 24
15. Detecting and Responding to MSE Failures . . . . . . . . . . 25
16. Transition Considerations . . . . . . . . . . . . . . . . . . 25
17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 26
18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
19. Security Considerations . . . . . . . . . . . . . . . . . . . 27
20. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27
21. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
21.1. Normative References . . . . . . . . . . . . . . . . . . 28
21.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference
Encoding . . . . . . . . . . . . . . . . . . . . . . 32
Appendix B. Prefix Length Considerations . . . . . . . . . . . . 34
Appendix C. VDL Mode 2 Considerations . . . . . . . . . . . . . 35
Appendix D. MN / AR Isolation Through L2 Address Mapping . . . . 36
Appendix E. Change Log . . . . . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
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1. Introduction
Mobile Nodes (MNs) (e.g., aircraft of various configurations,
terrestrial vehicles, seagoing vessels, mobile enterprise 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 a worldwide Internetwork 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.
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.
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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 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 multiple distinct upstream data link
connections that are managed together as a single logical unit.
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.
Mobility Service Endpoint (MSE)
an entity in the MS (either singluar 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)
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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.
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
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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.
Spanning Partitioned Administrative Networks (SPAN)
A means for bridging disjoint INET partitions as segments of a
unified OMNI link the same as for a bridged campus LAN. The SPAN
is a mid-layer IPv6 encapsulation service that supports a unified
OMNI link view for all segments.
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.
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The OMNI interface architectural layering model is the same as in
[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
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.
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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.
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.
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5. Maximum Transmission Unit (MTU) and Fragmentation
All IPv6 interfaces are REQUIRED to configure a minimum Maximum
Transmission Unit (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 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 IP
packets up to 9180 bytes while generating IPv6 Path MTU Discovery
(PMTUD) Packet Too Big (PTB) messages [RFC8201] as necessary (see
below).
OMNI interfaces employ mid-layer IPv6 encapsulation and
fragmentation/reassembly per [RFC2473] (also known as "SPAN
encapsulation" - see Section 8) to accommodate the 9180 byte MTU.
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 SPAN encapsulation and fragmentation/
reassembly as follows:
o When an OMNI interface sends a packet toward a final destination
via an ANET peer, it sends without SPAN encapsulation if the
packet is no larger than the underlying interface MTU. Otherwise,
it encapsulates the packet in a SPAN header with source address
set to the node's own SPAN address and destination set to the SPAN
address of the ANET peer. 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 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
without SPAN encapsulation if the destination is reached via an
INET address within the same SPAN segment. Otherwise, it
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encapsulates the packet in a SPAN header with source address set
to the node's SPAN address and destination set to the SPAN address
of the next hop OMNI node toward 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 is 1280 bytes and the smallest fragment
is no smaller than 640 bytes. The OMNI interface then sends the
fragments to the SPAN destination, which reassembles before
forwarding toward the final destination.
In order to avoid a "tiny fragment" attack, OMNI interfaces
unconditionally drop all SPAN fragments smaller than 640 bytes. In
order to set the correct context for reassembly, the OMNI interface
that inserts a SPAN header MUST also be the one that inserts the IPv6
Fragment Header Identification value. Although all fragmnets of the
same fragmented SPAN packet are typically sent via the same
underlying interface, this is not strictly required since all
fragments will arrive at the OMNI interface that performs reassembly
even if they travel over different paths.
Note that the OMNI interface can forward large packets via
encapsulation and fragmentation while at the same time returning
advisory PTB messages, e.g., subject to rate limiting. The receiving
node that performs reassembly can also send advisory PTB messages if
reassembly conditions become unfavorable. The AERO interface can
therefore continuously forward large packets without loss while
returning advisory messages recommending a smaller size. Advisory
PTB messages are differentiated from PTB messages that report loss by
setting the Code field in the ICMPv6 message header to the value 1.
This document therefore updates [RFC4443] and [RFC8201].
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
OMNI interfaces assign IPv6 Link-Local Addresses (i.e., "OMNI LLAs")
using the following constructs:
o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP
within the least-significant 112 bits of the the IPv6 link-local
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prefix fe80::/16. For example, for the MNP
2001:db8:1000:2000::/56 the corresponding LLA is
fe80:2001:db8:1000:2000::/72. See: [RFC4291], Section 2.5.6) for
a discussion of IPv6 link-local addresses, for which this document
presents an OMNI interface-specific adaptation. See Appendix B
for further discussion on prefix lengths.
o IPv4-compatible MN OMNI LLAs are assigned 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. (Note that distinct OMNI link segments can avoid overlap by
assigning MS OMNI LLAs from unique fe80::/96 sub-prefixes. For
example, a first segment could assign from fe80::1000/116, a
second from fe80::2000/116, a third from fe80::3000/116, etc.
o The OMNI LLA range fe80::/32 is used as the Teredo service prefix
for OMNI interfaces according to the format 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.
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. The SPAN
OMNI links employ an overlay network instance called "The SPAN"
(Spanning Partitioned Administrative Networks) that supports
forwarding of encapsulated link-scoped messages over a private IPv6
routing instance that spans the entire link without decrementing the
(link-local) Hop Limit. The OMNI link reserves the Unique Local
Address (ULA) prefix fd80::/16 [RFC4193] used for mapping OMNI LLAs
to routable SPAN addresses.
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SPAN addresses are configured in one-to-one correspondence with MN/MS
OMNI LLAs by simply zeroing bit 7 of the LLA. For example:
o the SPAN address corresponding to fe80:2001:db8:1:2:: is simply
fd80:2001:db8:1:2::
o the SPAN address corresponding to fe80::ffff:192.0.2.1 is simply
fd80::ffff:192.0.2.1
o the SPAN address corresponding to fe80::1000 is simply fd80::1000
The SPAN address 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 SPAN extends over the entire OMNI link to include the
MNs, but SPAN encapsulation is omitted over ANET links when possible
to conserve bandwidth (see: Section 11).
A full discussion of the SPAN 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:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
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 8.1.
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:
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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
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
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.
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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)
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
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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").
* 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''
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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 showin 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]. If additional P[*] blocks follow, their values
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 ommitted in the
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):
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* 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.
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.
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10. Address Mapping - Multicast
The multicast address mapping of the native underlying interface
applies. The mobile router on board the aircraft also serves as an
IGMP/MLD Proxy for its EUNs and/or hosted applications per [RFC4605]
while using the L2 address of the router as the L2 address for all
multicast packets.
11. Conceptual Sending Algorithm
The MN's IPv6 layer selects the outbound OMNI interface according to
standard IPv6 requirements when forwarding data packets from local or
EUN applications to external correspondents. The 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 multilink parameters 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 SPAN encapsulation if the packet does
not require fragmentation and the neighbor can determine the SPAN
addresses through other means (e.g., the packet's OMNI LLAs, neighbor
cache information, etc.). Otherwise, the OMNI interface inserts a
SPAN header and performs fragmentation if necessary.
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 associate with multiple MS instances concurrently. Each MS
instance represents a distinct OMNI link distinguished by its
associated MSPs. 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.
Depending on local policy and configuration, an MN may choose between
alternative active OMNI interfaces using a packet's DSCP, routing
information or static configuration. Interface selection based on
per-packet source addresses is also enabled when the MSPs for each
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OMNI interface are known (e.g., discovered through Prefix Information
Options (PIOs) and/or Route Information Options (RIOs)).
Each OMNI interface can be configured over the same or different sets
of underlying interfaces. Each ANET distinguishes between the
different OMNI links based on the MSPs represented in per-packet IPv6
addresses.
Multiple distinct OMNI links can therefore be used to support fault
tolerance, load balancing, reliability, etc. The architectural model
parallels Layer 2 Virtual Local Area Networks (VLANs), where the MSPs
serve as (virtual) VLAN tags.
12. Router Discovery and Prefix Registration
MNs interface with the MS by sending RS messages with OMNI options
under the assumption that a single AR on the ANET will proocess 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
address set to 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 indiviual 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
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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], 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.
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:
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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
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.
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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.
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 verifys that the MN is authorized
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.
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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 the MN via the ANET interface with an
OMNI 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
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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 D. 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 that connect to the open Internet via INET interfaces
can apply symmetric security services such as VPNs to establish
secured tunnels to MSEs. In environments where an explicit VPN may
be too restrictive, OMNI interfaces can instead ensure neighbor cache
integrity using SEcure Neighbor Discovery (SEND) [RFC3971] and
Cryptographically Generated Addresses (CGAs) [RFC3972].
When SEND/CGA are used, the IPv6 ND control plane messages used to
establish neighbor cache state are authenticated while data plane
messages are delivered the same as for ordinary best-effort Internet
traffic. Instead, data plane communications via OMNI interfaces that
connect over the open Internet without an explicit VPN must emply
transport- or higher-layer security to ensure integrity and/or
confidentiality.
In addition to secured OMNI interface RS/RA exchanges, SEND/CGA
supports safe address resolution and neighbor unreachability
detection as discused in Asymmetric Extended Route Optimization
(AERO) [I-D.templin-intarea-6706bis]. This allows for efficient
multilink operations over the open Internet with assured neighbor
cache integrity.
OMNI interfaces in the open Internet are often located behind Network
Address Translators (NATs). The OMNI interface accommodates NAT
traversal using the OMNI LLA prefix fe80::/32 for Teredo IPv6
addresses formatted as discussed in Section 4 of [RFC4380]. Further
specifications for NAT traversal are discussed in
[I-D.templin-intarea-6706bis][RFC6081][RFC4380].
18. 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].
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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]
6-252 Unassigned
253-254 Experimental [RFCXXXX]
255 Reserved [RFCXXXX]
Figure 13: OMNI Option Sub-Type Values
19. 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 synchronized
transaction confirmation is needed.
OMNI interfaces configured over secured underlying ANET interfaces
inherit the physical and/or link-layer security aspects of the
connected ANETs. OMNI interfaces configured over open Internet
interfaces must use symmetric securing services such as VPNs or
asymmetric services such as SEND/CGA [RFC3971][RFC3972].
Security considerations for specific access network interface types
are covered under the corresponding IP-over-(foo) specification
(e.g., [RFC2464], [RFC2492], etc.).
20. 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.
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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.
21. References
21.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[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>.
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[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>.
[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>.
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[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>.
21.2. Informative References
[I-D.templin-intarea-6706bis]
Templin, F., "Asymmetric Extended Route Optimization
(AERO)", draft-templin-intarea-6706bis-41 (work in
progress), April 2020.
[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
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[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>.
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:
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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)=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 14: Example 1: Dense 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|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 15: Example 2: Sparse 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|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 16: Example 3: Indexed Encoding
Appendix B. Prefix Length Considerations
The 64-bit boundary in IPv6 addresses [RFC7421] would suggest an MN
OMNI LLA that encodes the most-significant 64 MNP bits into the
least-significant 64 bits of the prefix fe80::/64. For example, the
MNP 2001:db8:1000:2000::/56 would be encoded as the OMNI addresss
fe80::2001:db8:1000:2000. However, the address juxtapositioning does
not present a form compatible with natural longest-prefix-match
routing.
[RFC4291] defines the link-local address format as the most
significant 10 bits of the prefix fe80::/10, followed by 54 unused
bits, followed by the least-significant 64 bits of the address. If
the 64-bit boundary is ignored for the purpose of this specification,
then the 54 unused bits can be employed for extended coding of MNPs
longer than /64.
One possible extended coding format would continue to encode MNP bits
0-63 in bits 64-127 of the OMNI LLA, while including MNP bits 64-117
in bits 10-63. For example, the OMNI LLA corresponding to the MNP
2001:db8:1111:2222:3333:4444:5555::/112 would be
fe8c:ccd1:1115:5540:2001:db8:1111:2222/128, and would still be a
valid IPv6 LLA per [RFC4291]. However, the non-sequential bit
ordering would render the prefix partially unreadable and completely
incompatible with longest-prefix-match routing determiniations.
An alternate form of OMNI LLA construction could be employed by
embedding the MNP beginning with the most significant bit immediately
following bit 10 of the prefix fe80::/10. For example, the OMNI LLA
corresponding to the MNP 2001:db8:1111:2222:3333:4444:5555::/112
would be written as fe88:0043:6e04:4448:888c:ccd1:1115:5540/122.
This alternate form would be compatible with longest-prefix-match
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determinations. It has the disadvantages of requiring an unweildy
10-bit right-shift of a 16byte address, as well as presenting a non-
human-readable form.
As a result, the OMNI specification has elected to encode the MNP
canonically beginning at bit 16 of the prefix fe80::/16. For
example, the OMNI LLA corresponding to the MNP
2001:db8:1111:2222:3333:4444:5555::/112 would be written as
fe80:2001:db8:1111:2222:3333:4444:5555/128. This has the advantage
of providing a natural coding scheme compatible with longest-prefix-
match, while presenting a human readalbe form and simple address
configuration through natural 16-bit word shifts. It has the
disadvantage that bits 10-15 of the address are unused; hence, the
longest prefix length that can be encoded is /112.
Appendix C. VDL Mode 2 Considerations
ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2"
(VDLM2) that specifies an essential radio frequency data link service
for aircraft and ground stations in worldwide civil aviation air
traffic management. The VDLM2 link type is "multicast capable"
[RFC4861], but with considerable differences from common multicast
links such as Ethernet and IEEE 802.11.
First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of
magnitude less than most modern wireless networking gear. Second,
due to the low available link bandwidth only VDLM2 ground stations
(i.e., and not aircraft) are permitted to send broadcasts, and even
so only as compact layer 2 "beacons". Third, aircraft employ the
services of ground stations by performing unicast RS/RA exchanges
upon receipt of beacons instead of listening for multicast RA
messages and/or sending multicast RS messages.
This beacon-oriented unicast RS/RA approach is necessary to conserve
the already-scarce available link bandwidth. Moreover, since the
numbers of beaconing ground stations operating within a given spatial
range must be kept as sparse as possible, it would not be feasible to
have different classes of ground stations within the same region
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].
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Appendix D. 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
coordinations 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 18). 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.
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 E. Change Log
<< RFC Editor - remove prior to publication >>
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 udates RFC4443 and RFC8201.
Differences from draft-templin-6man-omni-interface-10 to draft-
templin-6man-omni-interface-11:
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o Removed /64 assumption, resulting in new OMNI address format.
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 Explanded "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 dicussed 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 reserverd 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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