Address Resolution Protocol (ARP) for the Identifier-Locator Network Protocol for IPv4 (ILNPv4)
RFC 6747

Internet Research Task Force (IRTF)                          RJ Atkinson
Request for Comments: 6747                                    Consultant
Category: Experimental                                         SN Bhatti
ISSN: 2070-1721                                            U. St Andrews
                                                           November 2012

                   Address Resolution Protocol (ARP)
     for the Identifier-Locator Network Protocol for IPv4 (ILNPv4)

Abstract

   This document defines an Address Resolution Protocol (ARP) extension
   to support the Identifier-Locator Network Protocol for IPv4 (ILNPv4).
   ILNP is an experimental, evolutionary enhancement to IP.  This
   document 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/rfc6747.

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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 ....................................................3
      1.1. ILNP Document Roadmap ......................................3
      1.2. Terminology ................................................5
   2. ARP Extensions for ILNPv4 .......................................5
      2.1. ILNPv4 ARP Request Packet Format ...........................5
      2.2. ILNPv4 ARP Reply Packet Format .............................7
      2.3. Operation and Implementation of ARP for ILNPv4 .............8
   3. Security Considerations .........................................9
   4. IANA Considerations .............................................9
   5. References .....................................................10
      5.1. Normative References ......................................10
      5.2. Informative References ....................................11
   6. Acknowledgements ...............................................11

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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.

   At present, the Internet research and development community are
   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.  ILNP Document Roadmap

   This document describes extensions to ARP for use with
   ILNPv4.

   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

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   is based upon, and 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.

      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) [RFC6745] defines 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.

      g) [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 also defines a new IPv4
         Identifier Option used by ILNPv4 nodes.

      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.

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1.2.  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.  ARP Extensions for ILNPv4

   ILNP for IPv4 (ILNPv4) is merely a different instantiation of the
   ILNP architecture, so it retains the crisp distinction between the
   Locator and the Identifier.  As with ILNPv6, only the Locator
   values are used for routing and forwarding ILNPv4 packets
   [RFC6740].  As with ILNP for IPv6 (ILNPv6), when ILNPv4 is used
   for a network-layer session, the upper-layer protocols (e.g.,
   TCP/UDP pseudo-header checksum, IPsec Security Association) bind
   only to the Identifiers, never to the Locators [RFC6741].

   However, just as the packet format for IPv4 is different to IPv6,
   so the engineering details for ILNPv4 are different also.  While
   ILNPv6 is carefully engineered to be fully backwards-compatible
   with IPv6 Neighbor Discovery, ILNPv4 relies upon an extended
   version of the Address Resolution Protocol (ARP) [RFC826], which
   is defined here.  While ILNPv4 could have been engineered to avoid
   changes in ARP, that would have required that the ILNPv4 Locator
   (i.e., L32) have slightly different semantics, which was
   architecturally undesirable.

   The packet formats used are direct extensions of the existing
   widely deployed ARP Request (OP code 1) and ARP Reply (OP code 2)
   packet formats.  This design was chosen for practical engineering
   reasons (i.e., to maximise code reuse), rather than for maximum
   protocol design purity.

   We anticipate that ILNPv6 is much more likely to be widely
   implemented and deployed than ILNPv4.  However, having a clear
   definition of ILNPv4 helps demonstrate the difference between
   architecture and engineering, and also demonstrates that the
   common ILNP architecture can be instantiated in different ways
   with different existing network-layer protocols.

2.1.  ILNPv4 ARP Request Packet Format

   The ILNPv4 ARP Request is an extended version of the widely
   deployed ARP Request (OP code 1).  For experimentation purposes,
   the ILNPv4 ARP Request OP code uses decimal value 24.  It is
   important to note that decimal value 24 is a pre-defined,
   shared-use experimental OP code for ARP [RFC5494], and is not

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   uniquely assigned to ILNPv4 ARP Requests.  The ILNPv4 ARP Request
   extension permits the Node Identifier (NID) values to be carried
   in the ARP message, in addition to the node's 32-bit Locator
   (L32) values [RFC6742].

        0        7        15       23       31
        +--------+--------+--------+--------+
        |       HT        |        PT       |
        +--------+--------+--------+--------+
        |  HAL   |  PAL   |        OP       |
        +--------+--------+--------+--------+
        |         S_HA (bytes 0-3)          |
        +--------+--------+--------+--------+
        | S_HA (bytes 4-5)|S_L32 (bytes 0-1)|
        +--------+--------+--------+--------+
        |S_L32 (bytes 2-3)|S_NID (bytes 0-1)|
        +--------+--------+--------+--------+
        |         S_NID (bytes 2-5)         |
        +--------+--------+--------+--------+
        |S_NID (bytes 6-7)| T_HA (bytes 0-1)|
        +--------+--------+--------+--------+
        |         T_HA (bytes 3-5)          |
        +--------+--------+--------+--------+
        |         T_L32 (bytes 0-3)         |
        +--------+--------+--------+--------+
        |         T_NID (bytes 0-3)         |
        +--------+--------+--------+--------+
        |         T_NID (bytes 4-7)         |
        +--------+--------+--------+--------+

    Figure 2.1: ILNPv4 ARP Request packet format

   In Figure 2.1, the fields are as follows:

     HT      Hardware Type (*)
     PT      Protocol Type (*)
     HAL     Hardware Address Length (*)
     PAL     Protocol Address Length (uses new value 12)
     OP      Operation Code (uses experimental value OP_EXP1=24)
     S_HA    Sender Hardware Address (*)
     S_L32   Sender L32  (* same as Sender IPv4 address for ARP)
     S_NID   Sender Node Identifier (8 bytes)
     T_HA    Target Hardware Address (*)
     T_L32   Target L32  (* same as Target IPv4 address for ARP)
     T_NID   Target Node Identifier (8 bytes)

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   The changed OP code indicates that this is ILNPv4 and not IPv4.  The
   semantics and usage of the ILNPv4 ARP Request are identical to the
   existing ARP Request (OP code 2), except that the ILNPv4 ARP Request
   is sent only by nodes that support ILNPv4.

   The field descriptions marked with "*" should have the same values as
   for ARP as used for IPv4.

2.2.  ILNPv4 ARP Reply Packet Format

   The ILNPv4 ARP Reply is an extended version of the widely deployed
   ARP Reply (OP code 2).  For experimentation purposes, the ILNPv4 ARP
   Request OP code uses decimal value 25.  It is important to note that
   decimal value 25 is a pre-defined, shared-use experimental OP code
   for ARP [RFC5494], and is not uniquely assigned to ILNPv4 ARP
   Requests.  The ILNPv4 ARP Reply extension permits the Node Identifier
   (NID) values to be carried in the ARP message, in addition to the
   node's 32-bit Locator (L32) values [RFC6742].

        0        7        15       23       31
        +--------+--------+--------+--------+
        |       HT        |        PT       |
        +--------+--------+--------+--------+
        |  HAL   |  PAL   |        OP       |
        +--------+--------+--------+--------+
        |         S_HA (bytes 0-3)          |
        +--------+--------+--------+--------+
        | S_HA (bytes 4-5)|S_L32 (bytes 0-1)|
        +--------+--------+--------+--------+
        |S_L32 (bytes 2-3)|S_NID (bytes 0-1)|
        +--------+--------+--------+--------+
        |         S_NID (bytes 2-5)         |
        +--------+--------+--------+--------+
        |S_NID (bytes 6-7)| T_HA (bytes 0-1)|
        +--------+--------+--------+--------+
        |         T_HA (bytes 3-5)          |
        +--------+--------+--------+--------+
        |         T_L32 (bytes 0-3)         |
        +--------+--------+--------+--------+
        |         T_NID (bytes 0-3)         |
        +--------+--------+--------+--------+
        |         T_NID (bytes 4-7)         |
        +--------+--------+--------+--------+

    Figure 2.2: ILNPv4 ARP Reply packet format

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   In Figure 2.2, the fields are as follows:

     HT      Hardware Type (*)
     PT      Protocol Type (*)
     HAL     Hardware Address Length (*)
     PAL     Protocol Address Length (uses new value 12)
     OP      Operation Code (uses experimental value OP_EXP2=25)
     S_HA    Sender Hardware Address (*)
     S_L32   Sender L32  (* same as Sender IPv4 address for ARP)
     S_NID   Sender Node Identifier (8 bytes)
     T_HA    Target Hardware Address (*)
     T_L32   Target L32  (* same as Target IPv4 address for ARP)
     T_NID   Target Node Identifier (8 bytes)

   The changed OP code indicates that this is ILNPv4 and not IPv4.  The
   semantics and usage of the ILNPv4 ARP Reply are identical to the
   existing ARP Reply (OP code 2), except that the ILNPv4 ARP Reply is
   sent only by nodes that support ILNPv4.

   The field descriptions marked with "*" should have the same values as
   for ARP as used for IPv4.

2.3.  Operation and Implementation of ARP for ILNPv4

   The operation of ARP for ILNPv4 is almost identical to that for IPv4.
   Essentially, the key differences are:

      a) where an IPv4 ARP Request would use IPv4 addresses, an ILNPv4
         ARP Request MUST use:
         1. a 32-bit L32 value (_L32 suffixes in Figures 2.1 and 2.2)
         2. a 64-bit NID value (_NID suffixes in Figures 2.1 and 2.2)

      b) where an IPv4 ARP Reply would use IPv4 addresses, an ILNPv4 ARP
         Reply MUST use:
         1. a 32-bit L32 value (_L32 suffixes in Figures 2.1 and 2.2)
         2. a 64-bit NID value (_NID suffixes in Figures 2.1 and 2.2)

   As the OP codes 24 and 25 are distinct from ARP for IPv4, but the
   packet formats in Figures 2.1 and 2.2 are, effectively, extended
   versions of the corresponding ARP packets.  It should be possible to
   implement this extension of ARP by extending existing ARP
   implementations rather than having to write an entirely new
   implementation for ILNPv4.  It should be emphasised, however, that OP
   codes 24 and 25 are for experimental use as defined in [RFC5494], and
   so it is possible that other experimental protocols could be using
   these OP codes concurrently.

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3.  Security Considerations

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

   The existing widely deployed Address Resolution Protocol (ARP) for
   IPv4 is a link-layer protocol, so it is not vulnerable to off-link
   attackers.  In this way, it is a bit different than IPv6 Neighbor
   Discovery (ND); IPv6 ND is a subset of the Internet Control Message
   Protocol (ICMP), which runs over IPv6.

   However, ARP does not include any form of authentication, so current
   ARP deployments are vulnerable to a range of attacks from on-link
   nodes.  For example, it is possible for one node on a link to forge
   an ARP packet claiming to be from another node, thereby "stealing"
   the other node's IPv4 address.  [RFC5227] describes several of these
   risks and some measures that an ARP implementation can use to reduce
   the chance of accidental IPv4 address misconfiguration and also to
   detect such misconfiguration if it should occur.

   This extension does not change the security risks that are inherent
   in using ARP.

   In situations where additional protection against on-link attackers
   is needed (for example, within high-risk operational environments),
   the IEEE standards for link-layer security [IEEE-802.1-AE] SHOULD be
   implemented and deployed.

   Implementers of this specification need to understand that the two OP
   code values used for these 2 extensions are not uniquely assigned to
   ILNPv4.  Other experimenters might be using the same two OP code
   values at the same time for different ARP-related experiments.
   Absent prior coordination among all users of a particular IP
   subnetwork, different experiments might be occurring on the same IP
   subnetwork.  So, implementations of these two ARP extensions ought to
   be especially defensively coded.

4.  IANA Considerations

   This document makes no request of IANA.

   If in the future the IETF decided to standardise ILNPv4, then
   allocation of unique ARP OP codes for the two extensions above would
   be sensible as part of the IETF standardisation process.

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5.  References

5.1.  Normative References

   [IEEE-802.1-AE] IEEE, "Media Access Control (MAC) Security", IEEE
                   Standard 802.1 AE, 18 August 2006, IEEE, New York,
                   NY, 10016, USA.

   [RFC826]        Plummer, D., "Ethernet Address Resolution Protocol:
                   Or Converting Network Protocol Addresses to 48.bit
                   Ethernet Address for Transmission on Ethernet
                   Hardware", STD 37, RFC 826, November 1982.

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

   [RFC5227]       Cheshire, S., "IPv4 Address Conflict Detection", RFC
                   5227, July 2008.

   [RFC5494]       Arkko, J. and C. Pignataro, "IANA Allocation
                   Guidelines for the Address Resolution Protocol
                   (ARP)", RFC 5494, April 2009.

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

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

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

   [RFC6745]       Atkinson, R. and S. Bhatti,  "ICMP Locator Update
                   Message for the Identifier-Locator Network Protocol
                   for IPv4 (ILNPv4)", RFC 6745, 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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5.2.  Informative References

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

   [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.

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

6.  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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