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Internet Draft                                               RJ Atkinson
draft-rja-ilnp-icmp-11.txt                                    Consultant
Category: Experimental                                      27 July 2011
Expires: 27 JAN 2012

                      ICMP Locator Update message

Status of this Memo

   Distribution of this memo is unlimited.

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors. All rights reserved.

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   Internet-Drafts are working documents of the Internet
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   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."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   This document is not on the IETF standards-track and does not
   specify any level of standard.  This document merely provides
   information for the Internet community.

   This document has had extensive review within the IRTF Routing
   Research Group, and is part of the ILNP document set.  ILNP is
   one of the recommendations made by the RG Chairs.  Separately,
   various refereed research papers on ILNP have also been published
   during this decade.  So the ideas contained herein have had much
   broader review than the IRTF Routing RG.  The views in this
   document were considered controversial by the Routing RG,
   but the RG reached a consensus that the document still should be
   published.  The Routing RG has had remarkably little consensus
   on anything, so virtually all Routing RG outputs are considered


   This note specifies an experimental ICMPv6 message type used
   with the Identifier-Locator Network Protocol (ILNP).  This
   message is used to dynamically update Identifier/Locator
   bindings for an existing ILNP session.  This is a product
   of the  IRTF Routing RG.

Table of Contents

    1. Introduction ...........................................2
    2. Syntax..................................................3
    3. Transport Protocol Effects..............................5
    4. Implementation Considerations...........................5
    5. Backwards Compatibility.................................6
    6. Security Considerations ................................6
    7. IANA Considerations ....................................7
    8. References .............................................7

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1. Introduction

   At present, the research and development community are examining
   various alternatives for evolving the Internet Architecture.  Several
   different classes of evolution are being considered.  One class is
   often called "Map and Encapsulate", where traffic would be mapped and
   then tunnelled through the inter-domain core of the Internet.
   Another class being considered is sometimes known as
   "Identifier/Locator Split".  This document relates to a proposal that
   is in the latter class of evolutionary approaches.  In particular,
   the Identifier-Locator Network Protocol being described in this
   document and related Internet-Drafts is an evolution of IPv6. [ILNP-
   Intro] [ILNP-Nonce] [ILNP-DNS] [RFC 2460]

   The new ICMPv6 Locator Update message described in this document
   enables an ILNP-capable node to update its correspondents about the
   currently valid set of Locators valid to use in reaching the node
   sending this message.

   This new ICMPv6 message MUST NOT be used for IP sessions operating in
   classic IPv6 mode. This ICMPv6 message MUST ONLY be used for IP
   sessions that are operating in Identifier/Locator Split mode.
   Authentication is always required, as described in the Security
   Considerations section later in this note.

   Some might consider any and all use of ICMP to be undesirable.  In
   that context, please note that while this specification uses ICMP,
   there is no architectural difference between using ICMP and using
   some different framing, for example UDP.

1.1 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119. [RFC 2119]

2. Syntax

   Example ICMP message body for case where only 1 Locator value is
   being indicated:

   |  ICMP Type  |  ICMP Code    |        Checksum            |
   | Num of Locs |     RESERVED  |        Preference          |
   /                        Locator                           /

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   Example ICMP message body for case where 2 Locator
   values are being indicated:

   |  ICMP Type  |  ICMP Code    |        Checksum            |
   | Num of Locs |     RESERVED  |        Preference          |
   /                        Locator                           /
   |        RESERVED             |        Preference          |
   /                        Locator                           /

   For cases where more than 2 Locator values are being indicated,
   the "RESERVED", "Preference", and "Locator" fields are appended
   as appropriate to carry the intended number of Locator fields.

   ICMP Type:         This 8-bit field is set to the value XXX
                      to indicate that this is a Locator Update

   ICMP Code:         This 8-bit field indicates which kind of
                      ICMP Locator Update this is.  At present,
                      the only valid value is 0, which means
                      that this message contains all currently
                      valid Locator values for the sending node.

   Checksum:          This contains the ICMPv6 Checksum value
                      for this packet.

   Num of Locs:       This field contains the number of 64-bit
                      Locators that follow the RESERVED field.
                      This field must not contain the number zero,
                      as each ILNP node needs to be reachable via
                      at least 1 Locator value.  Multi-homed nodes
                      will have at least 2 Locator values.

   Reserved:          These fields MUST be sent as zero.
                      At this time, recipients should ignore the
                      contents of these field, as these bits are
                      reserved for future use.  (Implementers
                should understand that these fields might
                be used in the future.)

   Locator:           This 64-bit field contains a valid Locator

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                      that can be used to reach the sending node.
                      A variable number of Locator fields are
                      concatenated one after another.  These are
                      listed in priority order, with the first
                      Locator field containing the most preferred
                      Locator value.

   Preference:        A 16-bit unsigned integer which specifies
                the preference given to this Locator among
                other Locators in the same ICMP message.
                Lower Preference values are preferred
                over higher Preference values.

   NOTE: In order to prevent session stealing by an off-path
   adversary, all ICMP Locator Update packets MUST also contain
   an ILNP Nonce Destination Option with valid authentication
   information for the session associated with the ICMP Locator
   Update packet.  The ILNP Nonce Destination Option is required
   in all cases, even if some other authentication mechanism
   (e.g. IP Authentication Header) is also in use.[RFC 4302]

3.  Transport Protocol Effects

   This message has no impact on any transport protocol.

   The message may affect where packets for a given transport
   session are sent, but one of the design objectives for the
   I/L Split Mode (i.e. ILNP) is to decouple transport-protocols
   from network-layer changes.

4. Implementation Considerations

   Implementers may use any internal implementation they wish,
   provided that the external appearance is the same as this
   implementation approach.

   To support the Identifier/Locator Split operating mode, and
   retain the incremental deployability and backwards compatibility
   needed, the network layer needs a mode bit in the Transport Control
   Block (or its equivalent) to track which IP sessions are using
   the classic IPv6 mode and which IP sessions are using the
   Identifier/Locator Split mode.

   Further, when in the Identifier/Locator Split mode, nodes will
   need to retain a Correspondent Cache in the network layer that
   contains for each correspondent node:

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        - Source Identifier(s) in use
        - Source Locator(s) in use
        - Destination Identifier(s) in use
        - Destination Locator(s) in use
        - Session Nonce value from Local Node to Correspondent Node
        - Session Nonce value from Correspondent Node
             to Local Node

   Please also read the discussion of this Correspondent Cache in
   the companion document [ILNP-Intro].

   A node sending an ICMP Locator Update message will include all
   currently valid Locator values in that message.  A node receiving
   a valid ICMP Locator Update message MUST replace the previously
   current set of Locator values for that correspondent node in the
   ILNP Correspondent Cache with the newly received set of Locator

   Every implementation needs to support a large number of Locator
   values being sent or received in a single ICMP Locator Update
   message, because a multi-homed node or multi-homed site might
   have a large number of upstream links to different service
   providers, each with its own Locator value.

5.  Backwards Compatibility

   For all sessions operating in Identifier/Locator Split mode,
   inside each node the high-order 64-bits ("Locator") are always
   set to zero before the packet is sent upwards to the transport
   protocol.  So any changes in Locator values used on the wire
   will be invisible to the transport protocol.  In this mode,
   transport-layer checksums (e.g.  TCP pseudo-header checksum)
   will be calculated with both Source Locator and Destination
   Locator fields set to all zero.

   For recipient nodes or sessions operating in the classic
   IPv6 mode or otherwise not in the Identifier/Locator Split
   mode, the ICMP Locator Update packet MUST be discarded
   by the recipient without being processed.

6. Security Considerations

   The ICMP Locator Update message MUST ONLY be used for IP sessions
   operating in the Identifier/Locator Split mode.

   The experimental Nonce Destination Option [ILNP-Nonce] MUST be

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   present in packets containing an ICMPv6 Locator Update message.
   Further, the received Nonce Destination Option must contain the
   correct nonce value for the packet to be accepted by the
   recipient and then passed to the ICMPv6 protocol for
   processing. If either of these requirements are not met,
   the received packet MUST be discarded as not authentic,
   and a security event SHOULD be logged by the system receiving
   the non-authentic packet.

   For sessions operating in higher risk environments, the use
   of the IP Authentication Header *in addition* to the
   experimental Nonce Destination Option is recommended.
   Use of the IP Authentication Header to protect a packet
   does NOT permit the packet to be sent without the Nonce
   Destination Option.

   A broader discussion of ILNP Security Considerations is
   found in [ILNP-Intro], and is incorporated here by reference.

   Implementations need to support the case where a single
   ICMP Locator Update message contains a large number of
   Locator and Preference values and ought not develop a
   security fault (e.g. stack overflow) due to a received
   message containing more Locator values than expected.

7. IANA Considerations

   IANA is requested to assign a value, replacing the XXX,
   to the ICMP Type listed in Section 2, following the procedures
   in [RFC 4443].

   There are no other IANA actions for this document.

8.  References

8.1.  Normative References

   [RFC 2119]   Bradner, S., "Key words for use in RFCs to
                Indicate Requirement Levels", BCP 14, RFC 2119,
                March 1997.

   [RFC 2460]   S. Deering & R. Hinden, "Internet Protocol
                Version 6 Specification", RFC-2460,
                December 1998.

   [RFC 4302]   S. Kent, "IP Authentication Header", RFC 4302,
             December 2005.

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   [RFC 4443]   A. Conta, S. Deering, and M. Gupta (Ed.),
                "Internet Control Message Protocol (ICMPv6)
                for the Internet Protocol Version 6 (IPv6)
                Specification", RFC 4443, March 2006.

8.2.  Informative References

   [ILNP-Intro] Atkinson, R, "ILNP Concept of Operations",
                draft-rja-ilnp-intro-10.txt, February 2011.

   [ILNP-DNS]   Atkinson, R, "DNS Resource Records for ILNP",
                draft-rja-ilnp-dns-10.txt, February 2011.

   [ILNP-Nonce] Atkinson, R, "Nonce Destination Option",
                draft-rja-ilnp-nonce-10.txt, February 2011.


   Steve Blake, Mohamed Boucadair, Saleem Bhatti, Steve Hailes,
   Joel Halpern, Mark Handley, Volker Hilt, Tony Li, and Yakov
   Rehkter (in alphabetical order) provided review and feedback
   on earlier versions of this document.  Steve Blake provided
   an especially thorough review of the ILNP document set.

Author's Address

   RJ Atkinson
   McLean, VA
   22102 USA

   Email: rja.lists@gmail.com

   Expires: 7 AUG 2011

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