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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)


 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
 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

Atkinson & Bhatti Experimental [Page 1] RFC 6745 ILNPv4 ICMP November 2012

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
 ( 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.

Atkinson & Bhatti Experimental [Page 2] RFC 6745 ILNPv4 ICMP November 2012

 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

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.

Atkinson & Bhatti Experimental [Page 3] RFC 6745 ILNPv4 ICMP November 2012

 b) [RFC6741] describes engineering and implementation considerations
    that are common to both ILNPv4 and ILNPv6.
 c) [RFC6742] defines additional DNS resource records that support
 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]
 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.

Atkinson & Bhatti Experimental [Page 4] RFC 6745 ILNPv4 ICMP November 2012

 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",
 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]        |

Atkinson & Bhatti Experimental [Page 5] RFC 6745 ILNPv4 ICMP November 2012

    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
       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
        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.

Atkinson & Bhatti Experimental [Page 6] RFC 6745 ILNPv4 ICMP November 2012

 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

Atkinson & Bhatti Experimental [Page 7] RFC 6745 ILNPv4 ICMP November 2012

3. Transport Protocol Effects

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

Atkinson & Bhatti Experimental [Page 8] RFC 6745 ILNPv4 ICMP November 2012

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
 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
 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].

Atkinson & Bhatti Experimental [Page 9] RFC 6745 ILNPv4 ICMP November 2012

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
 [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.

Atkinson & Bhatti Experimental [Page 10] RFC 6745 ILNPv4 ICMP November 2012

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.

Atkinson & Bhatti Experimental [Page 11] RFC 6745 ILNPv4 ICMP November 2012

Authors' Addresses

 RJ Atkinson
 San Jose, CA 95125
 SN Bhatti
 School of Computer Science
 University of St Andrews
 North Haugh, St Andrews
 Fife  KY16 9SX
 Scotland, UK

Atkinson & Bhatti Experimental [Page 12]

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