[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06

Network Working Group                                    F. Templin, Ed.
Internet-Draft                              Boeing Research & Technology
Intended status: Standards Track                               A. Whyman
Expires: December 30, 2019               MWA Ltd c/o Inmarsat Global Ltd
                                                           June 28, 2019


   Transmission of IPv6 Packets over Aeronautical ("aero") Interfaces
                draft-templin-atn-aero-interface-03.txt

Abstract

   Mobile nodes (e.g., aircraft of various configurations) communicate
   with networked correspondents over multiple access network data links
   and configure mobile routers to connect their on-board networks.
   Mobile nodes configure a virtual interface (termed the "aero
   interface") as a thin layer over their underlying data link
   interfaces.  This document specifies the transmission of IPv6 packets
   over aeronautical ("aero") interfaces.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 30, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



Templin & Whyman        Expires December 30, 2019               [Page 1]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Aeronautical ("aero") Interface Model . . . . . . . . . . . .   4
   5.  Maximum Transmission Unit . . . . . . . . . . . . . . . . . .   6
   6.  Frame Format  . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Link-Local Addresses  . . . . . . . . . . . . . . . . . . . .   6
   8.  Address Mapping - Unicast . . . . . . . . . . . . . . . . . .   7
   9.  Address Mapping - Multicast . . . . . . . . . . . . . . . . .   9
   10. Conceptual Sending Algorithm  . . . . . . . . . . . . . . . .  10
     10.1.  Multiple Aero Interfaces . . . . . . . . . . . . . . . .  10
   11. Router and Prefix Discovery . . . . . . . . . . . . . . . . .  11
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   14. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     15.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Aero Option Extensions for Special-Purpose Links . .  16
   Appendix B.  Prefix Length Considerations . . . . . . . . . . . .  17
   Appendix C.  Change Log . . . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   Mobile Nodes (MNs) such as aircraft of various configurations may
   have multiple data links for communicating with networked
   correspondents.  These data links often have differing performance,
   cost and availability characteristics that can change dynamically
   according to mobility patterns, flight phases, proximity to
   infrastructure, etc.

   Each MN receives an IPv6 Mobile Network Prefix (MNP) that can be used
   by on-board networks regardless of the access network data links
   selected for data transport.  The MN performs router discovery the
   same as for customer edge routers [RFC7084], and acts as a mobile
   router on behalf of its on-board networks.  A virtual interface
   (termed the "aero interface") is configured as a thin layer over the
   underlying access network interfaces.

   The aero interface is therefore the only interface abstraction
   exposed to the IPv6 layer and behaves according to the Non-Broadcast,



Templin & Whyman        Expires December 30, 2019               [Page 2]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   Multiple Access (NBMA) interface principle, while underlying access
   network interfaces appear as link layer communication channels in the
   architecture.  The aero interface connects to a virtual overlay cloud
   service known as the "aero link".

   Each aero link has one or more associated Mobility Service Prefixes
   (MSPs) that identify the link.  An MSP is an aggregated IPv6 prefix
   from which aero link MNPs are derived.  If the MN connects to
   multiple aero links, then it configures a separate aero interface for
   each link.

   The aero interface interacts with the ground domain Mobility Service
   (MS) through control message exchanges based on IPv6 Neighbor
   Discovery [RFC4861].  The MS tracks MN movements and represents their
   MNPs in a global routing or mapping system.

   The aero interface provides a traffic engineering nexus for guiding
   inbound and outbound traffic to the correct underlying interface(s).
   The IPv6 layer sees the aero interface as a point of connection to
   the aero link; if there are multiple aero links (i.e., multiple
   MS's), the IPv6 layer will see multiple aero interfaces.

   This document specifies the transmission of IPv6 packets [RFC8200]
   and MN/MS control messaging over aeronautical ("aero") interfaces.

2.  Terminology

   The terminology in the normative references applies; especially, the
   terms "link" and "interface" are the same as defined in the IPv6
   [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications.

   The following terms are defined within the scope of this document:

   Access Network (ANET)
      a data link service network (e.g., an aviation radio access
      network, satellite service provider network, cellular operator
      network, etc.) protected by physical and/or link layer security.
      Each ANET connects to outside Internetworks via border security
      devices such as proxys, firewalls, packet filtering gateways, etc.

   ANET interface
      a node's attachment to a link in an ANET.

   Internetwork (INET)
      a connected network region with a coherent IP addressing plan that
      provides transit forwarding services for ANET mobile nodes and
      INET correspondents.  Examples include private enterprise
      networks, aviation networks and the global public Internet itself.



Templin & Whyman        Expires December 30, 2019               [Page 3]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   INET interface
      a node's attachment to a link in an INET.

   aero link
      a virtual overlay cloud service configured over one or more INETs
      and their connected ANETs.  An aero link may comprise multiple
      segments joined by bridges the same as for any link; the
      addressing plans in each segment may be mutually exclusive and
      managed by different administrative entities.

   aero interface
      a node's attachment to an aero link, and configured over one or
      more underlying ANET/INET interfaces.

   aero address
      an IPv6 link-local address constructed as specified in Section 7,
      and assigned to an aero interface.

3.  Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].  Lower case
   uses of these words are not to be interpreted as carrying RFC2119
   significance.

4.  Aeronautical ("aero") Interface Model

   An aero interface is a Mobile Node (MN) virtual interface configured
   over one or more ANET interfaces, which may be physical (e.g., an
   aeronautical radio link) or virtual (e.g., an Internet or higher-
   layer "tunnel").  The MN coordinates with the aero link Mobility
   Service (MS) through Router Solicitation (RS) / Router Advertisement
   (RA) and Neighbor Solicitation (NS) / Neighbor Advertisement (NA)
   message exchanges.

   The aero interface architectural layering model is the same as in
   [RFC7847], and augmented as shown in Figure 1.  The IPv6 layer
   therefore sees the aero interface as a single network layer interface
   with multiple underlying ANET interfaces that appear as link layer
   communication channels in the architecture.










Templin & Whyman        Expires December 30, 2019               [Page 4]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


                                     +----------------------------+
                                     |          TCP/UDP           |
              Session-to-IP    +---->|                            |
              Address Binding  |     +----------------------------+
                               +---->|            IPv6            |
              IP Address       +---->|                            |
              Binding          |     +----------------------------+
                               +---->|       aero Interface       |
              Logical-to-      +---->|       (aero address)       |
              Physical         |     +----------------------------+
              Interface        +---->|  L2  |  L2  |       |  L2  |
              Binding                |(IF#1)|(IF#2)| ..... |(IF#n)|
                                     +------+------+       +------+
                                     |  L1  |  L1  |       |  L1  |
                                     |      |      |       |      |
                                     +------+------+       +------+

           Figure 1: Aero Interface Architectural Layering Model

   The aero virtual interface model gives rise to a number of
   opportunities:

   o  since aero interface link-local addresses are uniquely derived
      from an MNP (see: Section 7, no Duplicate Address Detection (DAD)
      messaging is necessary over the aero interface.

   o  ANET interfaces can remain unnumbered in environments where
      communications are coordinated entirely over the aero interface.

   o  as ANET interface properties change (e.g., link quality, cost,
      availability, etc.), any active ANET interface can be used to
      update the profiles of multiple additional ANET interfaces in a
      single RS/RA message exchange.  This allows for timely adaptation
      and service continuity under dynamically changing conditions.

   o  coordinating ANET interfaces in this way allows them to be
      represented in a unified MS profile with provisions for mobility
      and multilink operations.

   o  exposing a single virtual interface abstraction to the IPv6 layer
      allows for traffic engineering (including QoS based link
      selection, packet replication, load balancing, etc.) at the link
      layer while still permitting queuing at the IPv6 layer based on,
      e.g., traffic class, flow label, etc.

   o  the IPv6 layer sees the aero interface as a point of connection to
      the aero link; if there are multiple aero links (i.e., multiple
      MS's), the IPv6 layer will see multiple aero interfaces.



Templin & Whyman        Expires December 30, 2019               [Page 5]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   Other opportunities are discussed in [RFC7847].

5.  Maximum Transmission Unit

   The aero interface and all underlying ANET interfaces MUST configure
   an MTU of at least 1280 bytes [RFC8200].  The aero interface SHOULD
   configure an MTU based on the largest MTU among all ANET interfaces.
   If the aero interface receives an RA message with an MTU option, it
   configures this new value regardless of any ANET interface MTUs.

   The aero interface returns internally-generated ICMPv6 "Packet Too
   Big" messages for packets that are no larger than the aero interface
   MTU but too large to traverse the selected underlying ANET interface.
   This ensures that the MTU is adaptive and reflects the ANET interface
   used for a given data flow.

6.  Frame Format

   The aero interface transmits IPv6 packets according to the native
   frame format of each underlying ANET interface.  For example, for an
   Ethernet interface the frame format is exactly as specified in
   [RFC2464], for tunnels over IPv6 the frame format is exactly as
   specified in [RFC2473], etc.

7.  Link-Local Addresses

   A MN "aero address" is an IPv6 link-local address with an interface
   identifier based on its assigned MNP.  MN aero addresses begin with
   the prefix fe80::/64 followed by a 64-bit prefix taken from the MNP
   (see: Appendix B).  For example, for the MNP:

      2001:db8:1000:2000::/56

   the corresponding aero addresses are:

      fe80::2001:db8:1000:2000

      fe80::2001:db8:1000:2001

      fe80::2001:db8:1000:2002

      ... etc. ...

      fe80::2001:db8:1000:20ff

   When the MN configures aero addresses from its MNP, it assigns them
   to the aero interface.  The lowest-numbered aero address serves as
   the "base" address (for example, for the MNP 2001:db8:1000:2000::/56



Templin & Whyman        Expires December 30, 2019               [Page 6]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   the base aero address is fe80::2001:db8:1000:2000).  The MN uses the
   base aero address for IPv6 ND messaging, but accepts packets destined
   to all aero addresses equally (i.e., the same as for any multi-
   addressed IPv6 interface).

   MS aero addresses are allocated from the range fe80::/96, and MUST be
   managed for uniqueness by the collective aero link administrative
   authorities.  Each address represents a distinct service endpoint in
   the MS.  The lower 32 bits of the address includes a unique integer
   value, e.g., fe80::1, fe80::2, fe80::3, etc.  The address fe80:: is
   reserved as the IPv6 link-local Subnet Router Anycast address
   [RFC4291], and the address fe80::ffff:ffff is reserved as the
   unspecified aero address; hence, these values are not available for
   general assignment.

   Since MN aero addresses are guaranteed unique by the nature of the
   unique MNP delegation, aero interfaces set the autoconfiguration
   variable DupAddrDetectTransmits to 0 [RFC4862].

8.  Address Mapping - Unicast

   Each aero interface maintains a neighbor cache for tracking per-
   neighbor state the same as for any IPv6 interface.  The aero
   interface uses standard IPv6 Neighbor Discovery (ND) messaging
   [RFC4861].

   IPv6 ND messages on aero interfaces use the native Source/Target
   Link-Layer Address Option (S/TLLAO) formats of the underlying ANET
   interfaces (e.g., for Ethernet the S/TLLAO is specified in
   [RFC2464]).

   Aero interfaces also use the link-local address format specified in
   Section 7, and aero interface IPv6 ND messages include aero options
   formatted as shown in Figure 2:

















Templin & Whyman        Expires December 30, 2019               [Page 7]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      Type     |   Length = 5  | Prefix Length |S|R|D| Reserved|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            ifindex            |           Reserved            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                                                               +
       |                                                               |
       +                  Mobile Network Prefix (MNP)                  +
       |                                                               |
       +                                                               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 2: Aero Option Format

   In this format:

   o  Type is set to TBD (to be assigned by IANA).

   o  Length is set to the constant value '5' (i.e., 5 units of 8
      octets).

   o  Prefix Length is set to the length of the prefix found in the
      Mobile Network Prefix (MNP) field.  For RS messages, the MS
      validates the MNP assertion, then announces the MNP in the routing
      system and returns an RA with Router Lifetime set to the MNP
      assertion lifetime.

   o  S (the 'Source' bit) is set to '1' in the aero options of an ND
      message that correspond to the ANET interface over which the ND
      message is sent, and set to '0' in all other aero options.

   o  R (the "Release" bit) is set to '1' in the aero option of an RS
      message sent for the purpose of withdrawing from the MS;
      otherwise, set to '0'.  The MS withdraws the MNP, then returns an
      RA with Router Lifetime set to '0'.




Templin & Whyman        Expires December 30, 2019               [Page 8]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   o  D (the "Disable" bit) is set to '1' in the aero option of an RS
      message for each ifIndex that is to be disabled in the recipient's
      neighbor cache entry; otherwise, set to '0'.  If the message
      contains multiple aero options the D value in each option is
      consulted.

   o  Both 'Reserved' fields are set to the value '0' on transmission.

   o  ifIndex is set to a 16-bit integer value corresponding to a
      specific underlying ANET interface as discussed in [RFC2863].
      Once the MN has assigned an ifIndex to an ANET interface, the
      assignment MUST remain unchanged until the MN disables the
      interface.  MNs MUST number each ifIndex with a value between '1'
      and '0xffff', and RA messages sent by the MS MUST set ifIndex to
      0.

   o  Mobile Network Prefix (MNP) is set to an IPv6 Prefix assigned to
      the MN.  Prefix Length and MNP in an RS message MUST be values
      that the MN is authorized to assert.  Otherwise, the MS ignores
      the RS message and does not enter the MNP into the routing/mapping
      system.

   o  P(i) is a set of Preferences that correspond to the 64
      Differentiated Service Code Point (DSCP) values [RFC2474].  Each
      P(i) is set to the value '0' ("disabled"), '1' ("low"), '2'
      ("medium") or '3' ("high") to indicate a QoS preference level for
      ANET interface selection purposes.

   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.
   From the perspective of ND, the aero interface would therefore appear
   to have multiple link layer addresses.  In that case, ND messages MAY
   include multiple aero options - each with an ifIndex that corresponds
   to a specific ANET interface.

   When an ND message includes aero options, the options corresponding
   to the underlying ANET interface used to transmit the message MUST
   set S to '1'.

9.  Address Mapping - Multicast

   The multicast address mapping of the native underlying ANET interface
   applies, and the ANET interacts with the MS for multicast forwarding
   and group management purposes.

   The mobile router on board the aircraft also serves as an IGMP/MLD
   Proxy for its EUNs and/or hosted applications per [RFC4605] while



Templin & Whyman        Expires December 30, 2019               [Page 9]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   using the link layer address of the router as the link layer address
   for all multicast packets.

10.  Conceptual Sending Algorithm

   The MN's IPv6 layer selects the outbound aero interface according to
   standard IPv6 requirements.  The aero interface maintains a default
   route and a neighbor cache entry for MS endpoints, and may also
   include additional neighbor cache entries created through other means
   (e.g., Address Resolution (AR), static configuration, etc.).

   When the MN sends packets via a MS endpoint, it may receive a
   Redirect message the same as for any IPv6 interface.  When the MN
   uses AR, the aero interface forwards NS messages to an MS endpoint
   (see: Section 11) which acts as a link-layer forwarding agent
   according to the NBMA link model.  The resulting NA message will
   provide link-layer address information for the neighbor.  When
   Neighbor Unreachability Detection (NUD) is used, the NS/NA exchange
   confirms reachability the same as for any IPv6 interface.

   After a packet enters the aero interface, an outbound ANET interface
   is selected based on traffic engineering information such as DSCP,
   application port number, cost, performance, etc.  Aero interface
   traffic engineering could also be configured to perform replication
   across multiple ANET interfaces for increased reliability at the
   expense of packet duplication.

   When a target neighbor has multiple link-layer addresses (each with a
   different traffic engineering profile), the aero interface selects
   ANET interfaces and neighbor link-layer addresses according to both
   its own outbound preferences and the inbound preferences of the
   target neighbor.

10.1.  Multiple Aero Interfaces

   MNs may associate with multiple MS instances concurrently.  Each MS
   instance represents a distinct aero link distinguished by its
   associated MSPs.  The MN configures a separate aero interface for
   each link so that multiple interfaces (e.g., aero0, aero1, aero2,
   etc.) are exposed to the IPv6 layer.

   Depending on local policy and configuration, an MN may choose between
   alternative active aero interfaces using a packet's DSCP, routing
   information or static configuration.  In particular, the MN can add
   the MSPs received in Prefix Information Options (PIOs) [RFC4861]
   [RFC8028] as guidance for aero interface selection based on per-
   packet source addresses .




Templin & Whyman        Expires December 30, 2019              [Page 10]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   Each aero interface can be configured over the same or different sets
   of ANET interfaces.  First hop ANET ARs distinguish between the
   different aero links based on the MSPs represented in per-packet IPv6
   addresses.

   Multiple distinct aero links can therefore be used to support fault
   tolerance, load balancing, reliability, etc.  The architectural model
   parallels Layer 2 Virtual Local Area Networks (VLANs), where the MSPs
   serve as (virtual) VLAN tags.

11.  Router and Prefix Discovery

   MNs interact with the MS through mobility extensions on first-hop
   ANET Access Routers (ARs).  MS extensions on ARs MUST examine the RS
   messages received on an ANET interface.  If the RS message includes
   aero options, the MS is invoked and an appropriate RA message is
   generated the same as for an IPv6 router.  If the RS message does not
   include aero options, the AR instead processes the RS message locally
   the same as for an ordinary IPv6 link.

   MNs configure aero interfaces that observe the properties discussed
   in the previous section.  The aero interface and its underlying
   interfaces are said to be in either the "UP" or "DOWN" state
   according to administrative actions in conjunction with the interface
   connectivity status.  An aero interface transitions to UP or DOWN
   through administrative action and/or through state transitions of the
   underlying interfaces.  When a first underlying interface transitions
   to UP, the aero interface also transitions to UP.  When all
   underlying interfaces transition to DOWN, the aero interface also
   transitions to DOWN.

   MNs coordinate with the MS through RS/RA exchanges via their aero
   interfaces.  When an aero interface transitions to UP, the MN sends
   initial RS messages with aero options to assert its MNP and register
   an initial set of underlying ANET interfaces that are also UP.  The
   MN sends additional RS messages to refresh MNP and/or router
   lifetimes, and to register/deregister underlying ANET interfaces as
   they transition to UP or DOWN.

   The MS sends RA messages with configuration information in response
   to a MN's RS message.  The RA includes a Router Lifetime value and
   PIOs with (A; L=0) that include MSPs for the link.  The configuration
   information may also include Route Information Options (RIO) options
   [RFC4191] with more-specific routes, and an MTU option that specifies
   the maximum acceptable packet size for the link.  The MS sends
   immediate unicast RA responses without delay; therefore, the
   'MAX_RA_DELAY_TIME' and 'MIN_DELAY_BETWEEN_RAS' constants for
   multicast RAs do not apply.  The MS MAY send periodic and/or event-



Templin & Whyman        Expires December 30, 2019              [Page 11]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   driven unsolicited RA messages, but is not required to do so for
   unicast advertisements [RFC4861].

   The MN sends RS messages from within the aero interface while using
   an UP underlying ANET interface as the outbound interface.  Each
   message is formatted as an ordinary RS message as though it
   originated from the IPv6 layer, but the process is coordinated wholly
   from within the aero interface and is therefore opaque to the IPv6
   layer.  The MN sends an initial RS message over an UP underlying
   interface with its base aero address as the source address, all-
   routers multicast as the destination address and with an aero option
   with a valid Prefix Length and MNP.  The aero option also sets S to 1
   and contains valid ifIndex and P(i) values appropriate for the
   underlying ANET interface.

   When the MS receives the RS, it accepts the message if the prefix
   assertion was acceptable; otherwise, it drops the message silently.
   If the prefix assertion was accepted, the MS injects the MNP into the
   routing/mapping system then caches the new ifIndex, Prefix Length,
   MNP and P(i) values.  The MS then returns an RA with the aero address
   of an MS endpoint as the source address, the aero address of the MN
   as the destination address and with Router Lifetime set to a non-zero
   value.

   After the MN receives the initial RA confirming the MNP assertion, it
   notes the aero address in the RA as the destination for all
   subsequent RS messages it sends via this MS endpoint.  If the MN
   needs to change to a different MS endpoint, it discovers and uses a
   different MS aero address.

   The MN then manages its underlying ANET interfaces according to their
   states as follows:

   o  When an underlying ANET interface transitions to UP, the MN sends
      an RS over the ANET interface with its base aero address as the
      source address, the MS aero address as the destination address,
      and with one or more aero options.  Aero options corresponding to
      the ANET interface set S to 1 and contain valid ifIndex and P(i)
      values appropriate for this ANET interface, while any additional
      aero options set S to 0 and contain valid ifIndex and P(i) values
      appropriate for other ANET interfaces.

   o  When an underlying ANET interface transitions to DOWN, the MN
      sends an RS over any UP ANET interface with an aero option for the
      DOWN ANET interface with D set to 1.  The RS may include
      additional aero options for additional ANET interfaces as above.





Templin & Whyman        Expires December 30, 2019              [Page 12]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   o  When a MN wishes to release from the current MS endpoint, it sends
      an RS message over any UP ANET interface with an aero option with
      R set to 1.  When the MS receives the RS message, it withdraws the
      MNP from the routing/mapping system and returns an RA message with
      Router Lifetime set to 0.

   o  When all of a MNs underlying interfaces have transitioned to DOWN,
      the MS withdraws the MNP the same as if it had received an RS with
      an aero option with R set to 1.

   The MN is responsible for retrying each RS/RA exchange up to
   MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL
   seconds until an RA is received.  If no RA is received over multiple
   UP ANET interfaces, the MN declares this MS endpoint unreachable and
   tries a different MS endpoint.

   The IPv6 layer sees the aero interface as an ordinary IPv6 interface.
   Therefore, when the IPv6 layer sends an RS message the aero interface
   returns an internally-generated RA message as though the message
   originated from an IPv6 router.  The internally-generated RA message
   contains configuration information (such as Router Lifetime, MTU,
   etc.) that is consistent with the information received from the RAs
   generated by the MS.

   Whether the aero interface RS/RA 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 RS/RA process
   until an RS is received from the IPv6 layer, while others may elect
   to initiate the RS/RA process independently of any IPv6 layer
   messaging.

12.  IANA Considerations

   The IANA is instructed to allocate an IPv6 Neighbor Discovery option
   type for the aero option in the IPv6 Neighbor Discovery Option
   Formats registry.

13.  Security Considerations

   Security considerations are the same as defined for the specific
   access network interface types, and readers are referred to the
   appropriate interface specifications.

   IPv6 and IPv6 ND security considerations also apply, and are
   specified in the normative references.






Templin & Whyman        Expires December 30, 2019              [Page 13]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


14.  Acknowledgements

   This document was prepared per the consensus decision at the 8th
   Conference of the International Civil Aviation Organization (ICAO)
   Working Group-I Mobility Subgroup on March 22, 2019.  Attendees and
   contributors included: Guray Acar, Danny Bharj, Francois D'Humieres,
   Pavel Drasil, Nikos Fistas, Giovanni Garofolo, Vaughn Maiolla, Tom
   McParland, Victor Moreno, Madhu Niraula, Brent Phillips, Liviu
   Popescu, Jacky Pouzet, Aloke Roy, Greg Saccone, Robert Segers,
   Stephane Tamalet, Fred Templin, Bela Varkonyi, Tony Whyman, and
   Dongsong Zeng.

   The following individuals are acknowledged for their useful comments:
   Pavel Drasil, Zdenek Jaron.

   .

15.  References

15.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <https://www.rfc-editor.org/info/rfc4191>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

   [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>.







Templin & Whyman        Expires December 30, 2019              [Page 14]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/info/rfc4862>.

   [RFC8028]  Baker, F. and B. Carpenter, "First-Hop Router Selection by
              Hosts in a Multi-Prefix Network", RFC 8028,
              DOI 10.17487/RFC8028, November 2016,
              <https://www.rfc-editor.org/info/rfc8028>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

15.2.  Informative References

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
              <https://www.rfc-editor.org/info/rfc2464>.

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
              December 1998, <https://www.rfc-editor.org/info/rfc2473>.

   [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
              MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
              <https://www.rfc-editor.org/info/rfc2863>.

   [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
              "Internet Group Management Protocol (IGMP) / Multicast
              Listener Discovery (MLD)-Based Multicast Forwarding
              ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605,
              August 2006, <https://www.rfc-editor.org/info/rfc4605>.

   [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>.






Templin & Whyman        Expires December 30, 2019              [Page 15]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   [RFC7847]  Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface
              Support for IP Hosts with Multi-Access Support", RFC 7847,
              DOI 10.17487/RFC7847, May 2016,
              <https://www.rfc-editor.org/info/rfc7847>.

Appendix A.  Aero Option Extensions for Special-Purpose Links

   The aero option format specified in Section 8 includes a Length value
   of 5 (i.e., 5 units of 8 octets).  However, special-purpose aero
   links may extend the basic format to include additional fields and a
   Length value larger than 5.

   For example, adaptation of the aero interface to the Aeronautical
   Telecommunications Network with Internet Protocol Services (ATN/IPS)
   includes link selection preferences based on transport port numbers
   in addition to the existing DSCP-based preferences.  ATN/IPS nodes
   maintain a map of transport port numbers to 64 possible preference
   fields, e.g., TCP port 22 maps to preference field 8, TCP port 443
   maps to preference field 20, UDP port 8060 maps to preference field
   34, etc.  The extended aero option format for ATN/IPS is shown in
   Figure 3, where the Length value is 7 and the 'Q(i)' fields provide
   link preferences for the corresponding transport port number.





























Templin & Whyman        Expires December 30, 2019              [Page 16]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      Type     |   Length = 5  | Prefix Length |S|R|D| Reserved|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            ifIndex            |           Reserved            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                                                               +
       |                                                               |
       +                  Mobile Network Prefix (MNP)                  +
       |                                                               |
       +                                                               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Q00|Q01|Q02|Q03|Q04|Q05|Q06|Q07|Q08|Q09|Q10|Q11|Q12|Q13|Q14|Q15|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Q16|Q17|Q18|Q19|Q20|Q21|Q22|Q23|Q24|Q25|Q26|Q27|Q28|Q29|Q30|Q31|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Q32|Q33|Q34|Q35|Q36|Q37|Q38|Q39|Q40|Q41|Q42|Q43|Q44|Q45|Q46|Q47|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Q48|Q49|Q50|Q51|Q52|Q53|Q54|Q55|Q56|Q57|Q58|Q59|Q60|Q61|Q62|Q63|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 3: ATN/IPS Extended Aero Option Format

Appendix B.  Prefix Length Considerations

   The IPv6 addressing architecture [RFC4291] reserves the prefix ::/8;
   this assures that MNPs will not begin with ::32 so that MN and MS
   aero addresses cannot overlap.  Additionally, this specification
   currently observes the 64-bit boundary in IPv6 addresses [RFC7421].

   MN aero addresses insert the most-significant 64 MNP bits into the
   least-significant 64 bits of the prefix fe80::/64, however [RFC4291]
   defines the link-local prefix as fe80::/10 meaning "fe80" followed by
   54 unused bits followed by the least-significant 64 bits of the
   address.  Future versions of this specification may adapt the 54
   unused bits for extended coding of MNP prefixes of /65 or longer (up
   to /118).



Templin & Whyman        Expires December 30, 2019              [Page 17]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


Appendix C.  Change Log

   << RFC Editor - remove prior to publication >>

   Differences from draft-templin-atn-aero-interface-02 to draft-
   templin-atn-aero-interface-03:

   o  Sections re-arranged to match RFC4861 structure.

   o  Multiple aero interfaces

   o  Conceptual sending algorithm

   Differences from draft-templin-atn-aero-interface-01 to draft-
   templin-atn-aero-interface-02:

   o  Removed discussion of encapsulation (out of scope)

   o  Simplified MTU section

   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




Templin & Whyman        Expires December 30, 2019              [Page 18]


Internet-Draft          IPv6 over AERO Interfaces              June 2019


   First draft version (draft-templin-atn-aero-interface-00):

   o  Draft based on consensus decision of ICAO Working Group I Mobility
      Subgroup March 22, 2019.

Authors' Addresses

   Fred L. Templin (editor)
   Boeing Research & Technology
   P.O. Box 3707
   Seattle, WA  98124
   USA

   Email: fltemplin@acm.org


   Tony Whyman
   MWA Ltd c/o Inmarsat Global Ltd
   99 City Road
   London  EC1Y 1AX
   England

   Email: tony.whyman@mccallumwhyman.com




























Templin & Whyman        Expires December 30, 2019              [Page 19]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/