    Internet Research Task Force (IRTF)                          RJ Atkinson
    Request for Comments: 6745                                    Consultant
    Category: Experimental                                         SN Bhatti
    ISSN: 2070-1721                                            U. St Andrews
                                                               November 2012

                      ICMP Locator Update Message for the
             Identifier-Locator Network Protocol for IPv4 (ILNPv4)

    Abstract

       This note defines an experimental ICMP message type for IPv4 used
       with the Identifier-Locator Network Protocol (ILNP).  ILNP is an
       experimental, evolutionary enhancement to IP.  The ICMP message
       defined herein is used to dynamically update Identifier/Locator
       bindings for an existing ILNP session.  This is a product of the IRTF
       Routing Research Group.

    Status of This Memo

       This document is not an Internet Standards Track specification; it is
       published for examination, experimental implementation, and
       evaluation.

       This document defines an Experimental Protocol for the Internet
       community.  This document is a product of the Internet Research Task
       Force (IRTF).  The IRTF publishes the results of Internet-related
       research and development activities.  These results might not be
       suitable for deployment.  This RFC represents the individual
       opinion(s) of one or more members of the Routing Research Group of
       the Internet Research Task Force (IRTF).  Documents approved for
       publication by the IRSG are not a candidate for any level of Internet
       Standard; see Section 2 of RFC 5741.

       Information about the current status of this document, any errata,
       and how to provide feedback on it may be obtained at
       http://www.rfc-editor.org/info/rfc6745.

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    Copyright Notice

       Copyright (c) 2012 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
       (http://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.

       This document may not be modified, and derivative works of it may not
       be created, except to format it for publication as an RFC or to
       translate it into languages other than English.

    Table of Contents

       1. Introduction ....................................................2
          1.1. Document Roadmap ...........................................3
          1.2. ICMPv4 Locator Update ......................................4
          1.3. Terminology ................................................5
       2. ICMP Locator Update Message for ILNPv4 ..........................5
       3. Transport Protocol Effects ......................................8
       4. Implementation Considerations ...................................8
       5. Backwards Compatibility .........................................9
       6. Security Considerations .........................................9
       7. IANA Considerations ............................................10
       8. References .....................................................10
          8.1. Normative References ......................................10
          8.2. Informative References ....................................11
       9. Acknowledgements ...............................................11

    1.  Introduction

       This document is part of the ILNP document set, which has had
       extensive review within the IRTF Routing RG.  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 controversial.

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       At present, the Internet research and development community is
       exploring various approaches to evolving the Internet Architecture to
       solve a variety of issues including, but not limited to, scalability
       of inter-domain routing [RFC4984].  A wide range of other issues
       (e.g., site multihoming, node multihoming, site/subnet mobility, node
       mobility) are also active concerns at present.  Several different
       classes of evolution are being considered by the Internet research
       and development community.  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.

       The Identifier-Locator Network Protocol (ILNP) is a proposal for
       evolving the Internet Architecture.  It differs from the current
       Internet Architecture primarily by deprecating the concept of an IP
       Address and instead defining two new objects, each having crisp
       syntax and semantics.  The first new object is the Locator, a
       topology-dependent name for a subnetwork.  The other new object is
       the Identifier, which provides a topology-independent name for a
       node.

    1.1.  Document Roadmap

       This document describes a new ICMPv4 Locator Update message used by
       an ILNP node to inform its correspondent nodes of any changes to its
       set of valid Locators.

       The ILNP architecture can have more than one engineering
       instantiation.  For example, one can imagine a "clean-slate"
       engineering design based on the ILNP architecture.  In separate
       documents, we describe two specific engineering instances of ILNP.
       The term "ILNPv6" refers precisely to an instance of ILNP that is
       based upon, and is backwards compatible with, IPv6.  The term
       "ILNPv4" refers precisely to an instance of ILNP that is based upon,
       and backwards compatible with, IPv4.

       Many engineering aspects common to both ILNPv4 and ILNPv6 are
       described in [RFC6741].  A full engineering specification for either
       ILNPv6 or ILNPv4 is beyond the scope of this document.

       Readers are referred to other related ILNP documents for details not
       described here:

       a) [RFC6740] is the main architectural description of ILNP, including
          the concept of operations.

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       b) [RFC6741] describes engineering and implementation considerations
          that are common to both ILNPv4 and ILNPv6.

       c) [RFC6742] defines additional DNS resource records that support
          ILNP.

       d) [RFC6743] defines a new ICMPv6 Locator Update message used by an
          ILNP node to inform its correspondent nodes of any changes to its
          set of valid Locators.

       e) [RFC6744] defines a new IPv6 Nonce Destination Option used by
          ILNPv6 nodes (1) to indicate to ILNP correspondent nodes (by
          inclusion within the initial packets of an ILNP session) that the
          node is operating in the ILNP mode and (2) to prevent off-path
          attacks against ILNP ICMP messages.  This Nonce is used, for
          example, with all ILNP ICMPv6 Locator Update messages that are
          exchanged among ILNP correspondent nodes.

       f) [RFC6746] defines a new IPv4 Nonce Option used by ILNPv4 nodes to
          carry a security nonce to prevent off-path attacks against ILNP
          ICMP messages, and it also defines a new IPv4 Identifier Option
          used by ILNPv4 nodes.

       g) [RFC6747] describes extensions to Address Resolution Protocol
          (ARP) for use with ILNPv4.

       h) [RFC6748] describes optional engineering and deployment functions
          for ILNP.  These are not required for the operation or use of ILNP
          and are provided as additional options.

    1.2.  ICMPv4 Locator Update

       As described in [RFC6740] and [RFC6741], an ILNP for IPv4 (ILNPv4)
       node might need to inform correspondent ILNPv4 nodes of changes to
       the set of valid Locator values.  The new ICMPv4 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 [RFC2460]
       [RFC4443].

       This new ICMPv4 message MUST ONLY be used for ILNPv4 sessions.
       Authentication is always required, as described in the Security
       Considerations section later in this document.

       Some might consider any and all use of ICMP to be undesirable.

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       In that context, please note that while this specification uses ICMP,
       on grounds that this is a control message, there is no architectural
       difference between using ICMP and using some different framing, for
       example UDP.

    1.3.  Terminology

       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].

    2.  ICMP Locator Update Message for ILNPv4

       The ICMP for IPv4 message described in this section has ICMP Type 253
       (as defined for experimental use in Section 8 of [RFC4727]) and is
       used ONLY with a current ILNPv4 session.  This message enables an
       ILNPv4 node to advertise changes to the active Locator set for the
       ILNPv4 node that originates this message to its unicast ILNP
       correspondent nodes.  It also enables those correspondents to
       acknowledge receipt of the advertisement.

       This particular ICMP for IPv4 message MUST ONLY be used with ILNPv4
       sessions.  The Checksum field for this message is calculated
       identically as for any other IPv4 ICMP message.

       ICMP Locator Update message

           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      |     Code      |           Checksum            |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |  Num of Locs  |   Operation   |           RESERVED            |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          /                       Locator [1]                             /
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Preference [1]         |           Lifetime [1]        |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          /                       Locator [2]                             /
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Preference [2]         |           Lifetime [2]        |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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          ICMP Fields:

             Type                  253
                                   This type value is taken from Section 8
                                   of [RFC4727] and is allocated for
                                   experimental use.

             Code                  0

             Checksum              The  16-bit one's complement of the
                                   one's complement sum of the ICMP
                                   message, starting with the ICMP Type.
                                   For computing the checksum, the
                                   Checksum field is set to 0.

             Num of Locs           The number of 32-bit Locator values
                                   that are advertised in this message.

             Locator[i],           The 32-bit Locator values currently
              i = 1..Num of Locs   valid for the sending ILNPv4 node.

             Preference[i],        The preferability of each Locator[i],
              i = 1..Num of Locs   relative to other valid Locator[i]
                                   values.  The Preference numbers here
                                   are identical, both in syntax and
                                   semantics, to the Preference values
                                   for L32 records that are specified by
                                   [RFC6742].

             Lifetime[i]           The maximum number of seconds that this
              i = 1..Num of Locs   particular Locator may be considered
                                   valid.  Normally, this is identical
                                   to the DNS lifetime of the
                                   corresponding L32 record, if one
                                   exists.

              Operation            The value in this field indicates
                                   whether this is a Locator Update
                                   Advertisement (0x01) or a Locator
                                   Update Acknowledgement (0x02).

              RESERVED             A field reserved for possible future
                                   use.  At present, the sender MUST
                                   initialise this field to zero.
                                   Receivers should ignore this field at
                                   present.  The field might be used for
                                   some protocol function in future.

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       NOTE WELL:  The ICMP Type value is allocated for shared
                   experimental use in Section 8 of [RFC4727].
                   It is not uniquely assigned to ILNPv4.  So,
                   implementations need to code particularly
                   defensively as other IPv4 experiments might be
                   using this same ICMP Type value for an
                   entirely different purpose with a different
                   ICMP packet format.

       The Operation field has value 1 (hexadecimal 0x01) for a Locator
       Update Advertisement.  The Operation field has value 2 (hexadecimal
       0x02) for a Locator Update Acknowledgement.  All other values of the
       Operation field are reserved for future use by future revisions of
       this specification.

       A node whose set of valid Locators has changed MUST send Locator
       Update Advertisement messages to each correspondent node for each
       active unicast ILNP session.  For unicast ILNP sessions, the receiver
       of a valid (i.e., authentication checks all passed, advertisement is
       received from a current correspondent node) Locator Update
       Advertisement addressed to the receiver MUST send a Locator Update
       Acknowledgement back to the sender of the Locator Update
       Advertisement.  The Acknowledgement message body is identical to the
       received Advertisement message body, except for the Operation value.

       All ILNPv4 ICMP Locator Update messages MUST contain a valid ILNPv4
       Identifier Option and MUST contain an ILNPv4 Nonce Option.

       ILNPv4 ICMP Locator Update messages also MAY be protected using IP
       Security for ILNP [RFC6741] [RFC4301].  Deployments in high-threat
       environments SHOULD also protect ILNPv4 ICMP Locator Update messages
       using IPsec.  While IPsec Encapsulating Security Payload (ESP) can
       protect a payload, no form of IPsec ESP is able to protect an IPv4
       Option that appears prior to the ESP header.  Note that even when IP
       Security for ILNP is in use, the ILNPv4 Nonce Option still MUST be
       present.  This simplifies protocol processing, and it also means that
       a receiver can perform the inexpensive check of the Nonce value
       before performing any (potentially expensive) cryptographic
       calculation.

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    3.  Transport Protocol Effects

       The ICMP Locator Update message has no impact on any transport
       protocol.

       The ICMP Locator Update message might affect where packets for a
       given transport-layer session are sent, but an ILNP design objective
       is to decouple transport protocols (e.g., TCP, UDP, SCTP) and
       transport-layer sessions 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 ILNPv4, and to 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 IPv4 mode and which IP sessions are
       using ILNPv4 mode.

       Further, when supporting ILNPv4, nodes will need to support a
       Identifier Locator Communication Cache (ILCC) in the network layer as
       described in [RFC6741].

       A node sending an ICMP Locator Update message MUST 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 its own ILCC
       with the newly received set of Locator values.

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

       It should be noted that as the ICMP Type uses an experimental value
       from [RFC4727], care should be taken when using with other protocols
       also using experimental values.

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    5.  Backwards Compatibility

       This IPv4 ICMP message uses the same checksum calculations as any
       other IPv4 ICMP message.

       When ILNPv4 is not in use, the receiving IPv4 mode MUST discard the
       ICMP Locator Update packet without processing the packet.

    6.  Security Considerations

       Security considerations for the overall ILNP Architecture are
       described in [RFC6740].  Additional common security considerations
       are described in [RFC6741].  This section describes security
       considerations specific to ILNPv4 topics discussed in this document.

       The ICMPv4 Locator Update message MUST ONLY be used for ILNPv4
       sessions.

       The ILNPv4 Nonce Option [RFC6746] MUST be present in packets
       containing an ICMPv4 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 ICMPv4
       protocol for processing.  If either of these requirements are not
       met, the received packet MUST be discarded as a forgery, and a
       security event SHOULD be logged by the system receiving the non-
       authentic packet.

       ILNP sessions operating in higher risk environments SHOULD use IP
       Security for ILNP [RFC6741] [RFC4301] *in addition* to the ILNPv4
       Nonce Option.  Use of IP Security for ILNP to protect a packet does
       NOT permit the packet to be sent without the Nonce Option.

       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.

       If the ILNP Nonce value is predictable, then an off-path attacker
       might be able to forge data or control packets.  This risk also is
       mitigated by the existing common practice of IP Source Address
       filtering [RFC2827] [RFC3704].

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    7.  IANA Considerations

       This document makes no request of IANA.

       If in the future the IETF decided to standardise ILNPv4, then
       allocation of a unique ICMP Type for the Locator Update as part of
       the IETF standardisation process would be sensible.

    8.  References

    8.1.  Normative References

       [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.

       [RFC2460]   Deering, S. and R. Hinden, "Internet Protocol, Version 6
                   (IPv6) Specification", RFC 2460, December 1998.

       [RFC4443]   Conta, A., Deering, S., and M. Gupta, Ed., "Internet
                   Control Message Protocol (ICMPv6) for the Internet
                   Protocol Version 6 (IPv6) Specification", RFC 4443, March
                   2006.

       [RFC4301]   Kent, S. and K. Seo, "Security Architecture for the
                   Internet Protocol", RFC 4301, December 2005.

       [RFC4727]   Murphy, S., "BGP Security Vulnerabilities Analysis", RFC
                   4272, January 2006.

       [RFC6740]   Atkinson, R. and S. Bhatti, "Identifier-Locator Network
                   Protocol (ILNP) Architectural Description", RFC 6740,
                   November 2012.

       [RFC6747]   Atkinson, R. and S. Bhatti, "Address Resolution Protocol
                   (ARP) Extension for the Identifier-Locator Network
                   Protocol for IPv4 (ILNPv4)", RFC 6747, November 2012.

       [RFC6741]   Atkinson, R. and S. Bhatti, "Identifier-Locator Network
                   Protocol (ILNP) Engineering and Implementation
                   Considerations", RFC 6741, November 2012.

       [RFC6746]   Atkinson, R. and S.Bhatti, "IPv4 Options for the
                   Identifier-Locator Network Protocol (ILNP)", RFC 6746,
                   November 2012.

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    8.2.  Informative References

       [RFC2827]   Ferguson, P. and D. Senie, "Network Ingress Filtering:
                   Defeating Denial of Service Attacks which employ IP
                   Source Address Spoofing", BCP 38, RFC 2827, May 2000.

       [RFC3704]   Baker, F. and P. Savola, "Ingress Filtering for
                   Multihomed Networks", BCP 84, RFC 3704, March 2004.

       [RFC4984]   Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report
                   from the IAB Workshop on Routing and Addressing", RFC
                   4984, September 2007.

       [RFC6742]   Atkinson, R., Bhatti, S. and S. Rose, "DNS Resource
                   Records for the Identifier-Locator Network Protocol
                   (ILNP)", RFC 6742, November 2012.

       [RFC6748]   Atkinson, R. and S. Bhatti, "Optional Advanced Deployment
                   Scenarios for the Identifier-Locator Network Protocol
                   (ILNP)", RFC 6748, November 2012.

       [RFC6743]   Atkinson, R. and S. Bhatti, "ICMPv6 Locator Update
                   Message", RFC 6743, November 2012.

       [RFC6744]   Atkinson, R. and S. Bhatti, "IPv6 Nonce Destination
                   Option for the Identifier-Locator Network Protocol for
                   IPv6 (ILNPv6)", RFC 6744, November 2012.

    9.  Acknowledgements

       Steve Blake, Stephane Bortzmeyer, Mohamed Boucadair, Noel Chiappa,
       Wes George, Steve Hailes, Joel Halpern, Mark Handley, Volker Hilt,
       Paul Jakma, Dae-Young Kim, Tony Li, Yakov Rehkter, Bruce Simpson,
       Robin Whittle, and John Wroclawski (in alphabetical order) provided
       review and feedback on earlier versions of this document.  Steve
       Blake provided an especially thorough review of an early version of
       the entire ILNP document set, which was extremely helpful.  We also
       wish to thank the anonymous reviewers of the various ILNP papers for
       their feedback.

       Roy Arends provided expert guidance on technical and procedural
       aspects of DNS issues.

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    Authors' Addresses

       RJ Atkinson
       Consultant
       San Jose, CA 95125
       USA

       EMail: rja.lists@gmail.com

       SN Bhatti
       School of Computer Science
       University of St Andrews
       North Haugh, St Andrews
       Fife  KY16 9SX
       Scotland, UK

       EMail: saleem@cs.st-andrews.ac.uk

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