Transmission of IPv6 Packets
over Overlay Multilink Network (OMNI) InterfacesThe Boeing CompanyP.O. Box 3707SeattleWA98124USAfltemplin@acm.orgMWA Ltd c/o Inmarsat Global Ltd99 City RoadLondonEC1Y 1AXEnglandtony.whyman@mccallumwhyman.comI-DInternet-DraftMobile 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.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 ) 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 ).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
. 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 and MN/MS control messaging over OMNI interfaces.The terminology in the normative references applies; especially, the
terms "link" and "interface" are the same as defined in the IPv6 and IPv6 Neighbor Discovery (ND) specifications. Also, the Protocol Constants defined
in Section 10 of 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 (with Link-Local scope assumed).The following terms are defined within the scope of this
document: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.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.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.an entity in
the MS (either singluar or aggregate) that coordinates the mobility
events of one or more MN.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.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.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.a first-hop router in the
ANET for connecting MNs to correspondents in outside
Internetworks.a MN's attachment to a link in
an ANET.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.a node's attachment to a link
in an INET.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.a node's attachment to an OMNI
link, and configured over one or more underlying ANET/INET
interfaces.an IPv6
link-local address constructed as specified in , and assigned to an OMNI interface.an IPv6 Neighbor Discovery option
providing multilink parameters for the OMNI interface as specified
in .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.The second layer in the OSI network model.
Also known as "layer-2", "link-layer", "sub-IP layer", "data link
layer", etc.The third layer in the OSI network model.
Also known as "layer-3", "network-layer", "IPv6 layer", etc.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.Each
MSE and AR is assigned a unique 32-bit Identification (MSID) as
specified in .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.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
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.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 and assigns the LLA to the OMNI interface.The OMNI interface architectural layering model is the same as in
, and augmented as shown in . 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.| |
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 |
| | | | |
+------+------+ +------+
]]>The OMNI virtual interface model gives rise to a number of
opportunities:since OMNI LLAs are uniquely derived from an MNP, no Duplicate
Address Detection (DAD) or Muticast Listener Discovery (MLD)
messaging is necessary.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.)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.coordinating ANET interfaces in this way allows them to be
represented in a unified MS profile with provisions for mobility and
multilink operations.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.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 . 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. \
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 ----> .
...........................................................
]]>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.All IPv6 interfaces are REQUIRED to configure a minimum Maximum
Transmission Unit (MTU) of 1280 bytes . The
network therefore MUST forward packets of at least 1280 bytes without
generating an IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB)
message .The OMNI interface configures an MTU of 9180 bytes ; 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 employs mid-layer IPv6 encapsulation and
fragmentation/reassembly per if necssary to
accommodate large packets. The interface returns internally-generated
PTB messages for packets admitted into the interface that it deems too
large for outbound underlying interfaces (e.g., according to underlying
interface performance characteristics, cost, MTU, etc). For all other
packets, the OMNI interface performs PMTUD even if the destination
appears to be on the same link since an OMNI link node on the path could
return a PTB message. This ensures that the path MTU is adaptive and
reflects the current path used for a given data flow.For underlying interfaces that have sufficiently large MTUs, the MN's
OMNI interface sends packets according to the ANET interface L2 frame
format without fragmentation. For all other cases, the OMNI interface
encapsulates the packet in a mid-layer IPv6 header with source address
set to the MN's SPAN address and destination set to the SPAN address
corresponding to the packet's destination (see: ). The OMNI interface then uses IPv6
fragmentation to break the encapsulated packet into a minimum number of
non-overlapping fragments, where the smallest fragment generated MUST be
no smaller than 640 bytes. For ANET interfaces that connect via ARs, the
largest fragment size is determined by the ANET interface MTU, while for
other underllying interface types the largest fragment size MUST be 1280
bytes. (Note that the outbound fragments can further be spread across
multiple underlying interfaces, since they will be reassembled by the
OMNI interface closest to the final destination.)When an AR receives a fragmented or whole packet from the INET
destined to an ANET MN, it first determines whether to forward or drop
and return a PTB. If the AR deems the packet to be of acceptable size,
it first re-adjusts fragment sizes (if necessary) then forwards the
packet/fragments to the MN. If the packet is no larger than the ANET
MTU, the AR forwards according to the ANET L2 frame format. If the
packet is larger than the ANET MTU, the AR instead uses IPv6
encapsulation and fragmentation as above. The MN then reassembles and
discards the encapsulation header, then forwards the whole packet to the
final destination.In order to avoid a "tiny fragment" attack, AERO nodes
unconditionally drop all fragments smaller than 640 bytes. In order to
set the correct context for reassembly, the AERO node that inserts a
SPAN header MUST also be the node that inserts the IPv6 Fragment Header
Identification value.Note also 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 OMNI interface can
therefore continuously forward large packets without loss while
returning advisory messages recommending a smaller size.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 , 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 , etc.OMNI interfaces assign IPv6 Link-Local Addresses (i.e., "OMNI LLAs")
using the following constructs: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
prefix fe80::/16. For example, for the MNP 2001:db8:1000:2000::/56
the corresponding LLA is fe80:2001:db8:1000:2000::/72. See: , Section 2.5.6) for a discussion of IPv6
link-local addresses, for which this document presents an OMNI
interface-specific adaptation. See for
further discussion on prefix lengths.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).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::) . The
MSID range 0xff00000000 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.)Since the prefix 0000::/8 is "Reserved by the IETF" , 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 .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 used for mapping OMNI
LLAs to routable SPAN addresses.SPAN addresses are configured in one-to-one correspondence with MN/MS
OMNI LLAs by simply zeroing bit 7 of the LLA. For example:the SPAN address corresponding to fe80:2001:db8:1:2:: is simply
fd80:2001:db8:1:2::the SPAN address corresponding to fe80::ffff:192.0.2.1 is simply
fd80::ffff:192.0.2.1the SPAN address corresponding to fe80::1000 is simply
fd80::1000The 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 . A full discussion of the SPAN appears in .OMNI interfaces maintain a neighbor cache for tracking per-neighbor
state and use the link-local address format specified in . IPv6 Neighbor Discovery (ND) 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
).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 :In this format:Type is set to TBD.Length is set to the number of 8 octet blocks in the option.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.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.Reserved is set to the value '0' on transmission and ignored on
reception.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.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: Sub-Type is a 1-byte field that encodes the Sub-Option type.
Sub-Options defined in this document are:Sub-Types 253 and 254 are reserved for experimentation,
as recommended in].Sub-Length is a 1-byte field that encodes the length of the
Sub-Option Data, in bytesSub-Option Data is a byte string with format determined by
Sub-TypeDuring 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:Sub-Type is set to 0.No Sub-Length or Sub-Option Data follows (i.e., the
"Sub-Option" consists of a single zero octet).Sub-Type is set to 1.Sub-Length is set to N-2 being the number of padding bytes
that follow.Sub-Option Data consists of N-2 zero-valued octets.Sub-Type is set to 2.Sub-Length is set to 4+N (the number of Sub-Option Data bytes
that follow).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
(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.
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: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 showin in ). 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] .
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".Sub-Type is set to 3.Sub-Length is set to 4+N (the number of Sub-Option Data bytes
that follow).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 .the remainder of the Sub-Option body encodes a
variable-length traffic selector formatted per , beginning with the "TS Format"
field.Sub-Type is set to 4.Sub-Length is set to 4.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.Sub-Type is set to 5.Sub-Length is set to 4.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.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 while using the L2 address of the router as the L2
address for all multicast packets.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.OMNI interface multilink service designers MUST observe the BCP
guidance in Section 15 in terms of implications
for reordering when packets from the same flow may be spread across
multiple underlying interfaces having diverse properties.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
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.MNs interface with the MS by sending RS messages with OMNI options
that include MSIDs. For each underlying interface, the MN sends an RS
message with an OMNI option with (R,A) flags, wth MS-Register/Release
suboptions, and with destination address set to All-Routers multicast
(ff02::2) . Example MSID discovery methods are
given in , 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, or associate with all MSEs by sending an RS with
MS-Register MSID set to 0xffffffff.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 with a valid Prefix Length, (R, A) flags,
ifIndex-tuples appropriate for underlying interfaces and with
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 , with an OMNI option with (R, A) flags, ifIndex
tuples and 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:PIOs with (A; L=0) that include MSPs for the link .RIOs with more-specific routes.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 .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 .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: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.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).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.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.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 finer-grained timescale than
the MN is required to do on its own behalf.ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP)
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.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) 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) .The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated
by small delays . 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.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 . 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 . This arrangement imparts a
(virtual) point-to-point link model over the (physical) multiple access
link.OMNI interfaces that connect to the open Internet via native and/or
NATed underlying 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) and Cryptographically Generated Addresses (CGAs)
.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) . This allows for efficient
multilink operations over the open Internet with assured neighbor cache
integrity.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 .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 .The IANA is instructed to allocate one Ethernet unicast address TBD2
(suggest 00-00-5E-00-52-14 ) in the registry
"IANA Ethernet Address Block - Unicast Use".Security considerations for IPv6 and IPv6
Neighbor Discovery apply. OMNI interface IPv6
ND messages SHOULD include Nonce and Timestamp options 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 .Security considerations for specific access network interface types
are covered under the corresponding IP-over-(foo) specification (e.g.,
, , etc.).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.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:The 64-bit boundary in IPv6 addresses 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. 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 . 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
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.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" , 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].Per , 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: ). 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) .<< RFC Editor - remove prior to publication >>Differences from draft-templin-6man-omni-interface-10 to
draft-templin-6man-omni-interface-11:Removed /64 assumption, resulting in new OMNI address format.Differences from draft-templin-6man-omni-interface-07 to
draft-templin-6man-omni-interface-08:OMNI MNs in the open InternetDifferences from draft-templin-6man-omni-interface-06 to
draft-templin-6man-omni-interface-07:Brought back L2 MSADDR mapping text for MN / AR isolation based
on L2 addressing.Explanded "Transition Considerations".Differences from draft-templin-6man-omni-interface-05 to
draft-templin-6man-omni-interface-06: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: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: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:Removed "Primary" flag and supporting text.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:"All-MSEs" OMNI LLA defined. Also reserverd fe80::ff00:0000/104
for future use (most likely as "pseudo-multicast").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:Minor clarification on Type-2 ifIndex-tuple encoding.Draft filename change (replaces
draft-templin-atn-aero-interface).Differences from draft-templin-atn-aero-interface-20 to
draft-templin-atn-aero-interface-21:OMNI option formatMTUDifferences from draft-templin-atn-aero-interface-19 to
draft-templin-atn-aero-interface-20:MTUDifferences from draft-templin-atn-aero-interface-18 to
draft-templin-atn-aero-interface-19:MTUDifferences from draft-templin-atn-aero-interface-17 to
draft-templin-atn-aero-interface-18:MTU and RA configuration information updated.Differences from draft-templin-atn-aero-interface-16 to
draft-templin-atn-aero-interface-17:New "Primary" flag in OMNI option.Differences from draft-templin-atn-aero-interface-15 to
draft-templin-atn-aero-interface-16:New note on MSE OMNI LLA uniqueness assurance.General cleanup.Differences from draft-templin-atn-aero-interface-14 to
draft-templin-atn-aero-interface-15:General cleanup.Differences from draft-templin-atn-aero-interface-13 to
draft-templin-atn-aero-interface-14:General cleanup.Differences from draft-templin-atn-aero-interface-12 to
draft-templin-atn-aero-interface-13: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:Removed "Request/Response" OMNI option formats. Now, there is
only one OMNI option format that applies to all ND messages.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:Changed name from "aero" to "OMNI"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:Renamed ARO option to AERO optionRe-worked Section 13 text to discuss proactive NUD.Differences from draft-templin-atn-aero-interface-08 to
draft-templin-atn-aero-interface-09:Version and reference updateDifferences from draft-templin-atn-aero-interface-07 to
draft-templin-atn-aero-interface-08:Removed "Classic" and "MS-enabled" link model discussionAdded new figure for MN/AR/MSE model.New Section on "Detecting and responding to MSE failure".Differences from draft-templin-atn-aero-interface-06 to
draft-templin-atn-aero-interface-07:Removed "nonce" field from AR option format. Applications that
require a nonce can include a standard nonce option if they want
to.Various editorial cleanups.Differences from draft-templin-atn-aero-interface-05 to
draft-templin-atn-aero-interface-06:New Appendix C on "VDL Mode 2 Considerations"New Appendix D on "RS/RA Messaging as a Single Standard API"Various significant updates in Section 5, 10 and 12.Differences from draft-templin-atn-aero-interface-04 to
draft-templin-atn-aero-interface-05:Introduced RFC6543 precedent for focusing IPv6 ND messaging to a
reserved unicast link-layer addressIntroduced new IPv6 ND option for Aero RegistrationSpecification of MN-to-MSE message exchanges via the ANET access
router as a proxyIANA 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:Removed MNP from aero option format - we already have RIOs and
PIOs, and so do not need another option type to include a
Prefix.Clarified that the RA message response must include an aero
option to indicate to the MN that the ANET provides a MS.MTU interactions with link adaptation clarified.Differences from draft-templin-atn-aero-interface-02 to
draft-templin-atn-aero-interface-03:Sections re-arranged to match RFC4861 structure.Multiple aero interfacesConceptual sending algorithmDifferences from draft-templin-atn-aero-interface-01 to
draft-templin-atn-aero-interface-02:Removed discussion of encapsulation (out of scope)Simplified MTU sectionChanged to use a new IPv6 ND option (the "aero option") instead
of S/TLLAOExplained the nature of the interaction between the mobility
management service and the air interfaceDifferences from draft-templin-atn-aero-interface-00 to
draft-templin-atn-aero-interface-01:Updates based on list review comments on IETF 'atn' list from
4/29/2019 through 5/7/2019 (issue tracker established)added list of opportunities afforded by the single virtual link
modeladded discussion of encapsulation considerations to Section 6noted that DupAddrDetectTransmits is set to 0removed 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.Significant re-work of "Router Discovery" section.New Appendix B on Prefix Length considerationsFirst draft version (draft-templin-atn-aero-interface-00):Draft based on consensus decision of ICAO Working Group I
Mobility Subgroup March 22, 2019.