Network Working Group                                           J. Arkko
Request for Comments: 5494                                      Ericsson
Updates: 826, 951, 1044, 1329, 2131,                        C. Pignataro
         2132, 2176, 2225, 2834, 2835,                     Cisco Systems
         3315, 4338, 4361, 4701                               April 2009
Category: Standards Track

  IANA Allocation Guidelines for the Address Resolution Protocol (ARP)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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 (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.


   This document specifies the IANA guidelines for allocating new values
   in the Address Resolution Protocol (ARP).  This document also
   reserves some numbers for experimentation purposes.  The changes also
   affect other protocols that employ values from the ARP name spaces.

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1.  Introduction

   This document specifies the IANA guidelines [RFC5226] for allocating
   new values for various fields in the Address Resolution Protocol
   (ARP) [RFC0826].  The change is also applicable to extensions of ARP
   that use the same message format, such as [RFC0903], [RFC1931], and

   The change also affects other protocols that employ values from the
   ARP name spaces.  For instance, the ARP hardware address type
   (ar$hrd) number space is also used in the "htype" (hardware address
   type) fields in the Bootstrap Protocol (BOOTP) [RFC0951] and Dynamic
   Host Configuration Protocol (DHCP) [RFC2131], as well as in the
   "hardware type" field in the DHCP Unique Identifiers in DHCPv6
   [RFC3315].  These protocols are therefore affected by the update in
   the IANA rules.  Other affected specifications include the
   specialized address resolution mechanisms in:

   o  HYPERchannel [RFC1044]

   o  DHCP options [RFC2132] [RFC4361]

   o  ATM (Asynchronous Transfer Mode) ARP [RFC2225]

   o  HARP (High-Performance Parallel Interface ARP) [RFC2834] [RFC2835]

   o  Dual MAC (Media Access Control) FDDI (Fiber Distributed Data
      Interface) ARP [RFC1329]

   o  MAPOS (Multiple Access Protocol over Synchronous Optical Network/
      Synchronous Digital Hierarchy) ARP [RFC2176]

   o  FC (Fibre Channel) ARP [RFC4338]

   o  DNS DHCID Resource Record [RFC4701]

   The IANA guidelines are given in Section 2.  Previously, no IANA
   guidance existed for such allocations.  The purpose of this document
   is to allow IANA to manage number assignments based on these
   guidelines in a consistent manner.

   This document also reserves some numbers for experimentation
   purposes.  These numbers are given in Section 3.

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2.  IANA Considerations

   The following rules apply to the fields of ARP:

   ar$hrd (16 bits) Hardware address space

      Requests for ar$hrd values below 256 or for a batch of more than
      one new value are made through Expert Review [RFC5226].

      Note that certain protocols, such as BOOTP and DHCPv4, employ
      these values within an 8-bit field.  The expert should determine
      that a need to allocate the new values exists and that the
      existing values are insufficient to represent the new hardware
      address types.  The expert should also determine the applicability
      of the request and assign values higher than 255 for requests that
      do not apply to BOOTP/DHCPv4.  Similarly, the expert should assign
      1-octet values for requests that apply to BOOTP/DHCPv4, as for
      example the "IPsec tunnel" with value 31 [RFC3456].  Conversely,
      ARP-only uses, without a foreseeable reason to use the same value
      in BOOTP/DHCPv4, should favor 2-octet values.

      Requests for individual new ar$hrd values that do not specify a
      value, or where the requested value is greater than 255, are made
      through First Come First Served [RFC5226].  The assignment will
      always result in a 2-octet value.

   ar$pro (16 bits) Protocol address space

      These numbers share the Ethertype space.  The Ethertype space is
      administered as described in [RFC5342].

   ar$op (16 bits) Opcode

      Requests for new ar$op values are made through IETF Review or IESG
      Approval [RFC5226].

3.  Allocations Defined in This Document

   When testing new protocol extension ideas, it is often necessary to
   use an actual constant in order to use the new function, even when
   testing in a closed environment.  This document reserves the
   following numbers for experimentation purposes in ARP:

   o  Two new ar$hrd values are allocated for experimental purposes:
      HW_EXP1 (36) and HW_EXP2 (256).  Note that these two new values
      were purposely chosen so that one would be below 256 and the other
      would be above 255, and so that there would be different values in
      the least and most significant octets.

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   o  Two new values for the ar$op are allocated for experimental
      purposes: OP_EXP1 (24) and OP_EXP2 (25).

   Note that Appendix B.2 of [RFC5342] lists two Ethertypes that can be
   used for experimental purposes.

   In addition, for both ar$hrd and ar$op, the values 0 and 65535 are
   marked as reserved.  This means that they are not available for

4.  Security Considerations

   This specification does not change the security properties of the
   affected protocols.

   However, a few words are necessary about the use of the experimental
   code points defined in Section 3.  Potentially harmful side effects
   from the use of the experimental values need to be carefully
   evaluated before deploying any experiment across networks that the
   owner of the experiment does not entirely control.  Guidance given in
   [RFC3692] about the use of experimental values needs to be followed.

5.  Acknowledgments

   The lack of any current rules has come up as new values were
   requested from IANA, who contacted the IESG for advice.  The author
   would like to thank Michelle Cotton in particular for bringing up
   this issue.  The author would also like to thank Brian Carpenter,
   Thomas Narten, Scott Bradner, Donald Eastlake, Andrew G. Malis, Brian
   Haberman, Robert Sparks, Larry Zhu, and Dave Thaler for feedback.

6.  References

6.1.  Normative References

   [RFC0826]  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.

   [RFC0951]  Croft, B. and J. Gilmore, "Bootstrap Protocol", RFC 951,
              September 1985.

   [RFC1044]  Hardwick, K. and J. Lekashman, "Internet Protocol on
              Network System's HYPERchannel: Protocol specification",
              STD 45, RFC 1044, February 1988.

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   [RFC1329]  Kuehn, P., "Thoughts on Address Resolution for Dual MAC
              FDDI Networks", RFC 1329, May 1992.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.

   [RFC2176]  Murakami, K. and M. Maruyama, "IPv4 over MAPOS Version 1",
              RFC 2176, June 1997.

   [RFC2225]  Laubach, M. and J. Halpern, "Classical IP and ARP over
              ATM", RFC 2225, April 1998.

   [RFC2834]  Pittet, J., "ARP and IP Broadcast over HIPPI-800",
              RFC 2834, May 2000.

   [RFC2835]  Pittet, J., "IP and ARP over HIPPI-6400 (GSN)", RFC 2835,
              May 2000.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3692]  Narten, T., "Assigning Experimental and Testing Numbers
              Considered Useful", BCP 82, RFC 3692, January 2004.

   [RFC4338]  DeSanti, C., Carlson, C., and R. Nixon, "Transmission of
              IPv6, IPv4, and Address Resolution Protocol (ARP) Packets
              over Fibre Channel", RFC 4338, January 2006.

   [RFC4361]  Lemon, T. and B. Sommerfeld, "Node-specific Client
              Identifiers for Dynamic Host Configuration Protocol
              Version Four (DHCPv4)", RFC 4361, February 2006.

   [RFC4701]  Stapp, M., Lemon, T., and A. Gustafsson, "A DNS Resource
              Record (RR) for Encoding Dynamic Host Configuration
              Protocol (DHCP) Information (DHCID RR)", RFC 4701,
              October 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5342]  Eastlake. , D., "IANA Considerations and IETF Protocol
              Usage for IEEE 802 Parameters", BCP 141, RFC 5342,
              September 2008.

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6.2.  Informative References

   [RFC0903]  Finlayson, R., Mann, T., Mogul, J., and M. Theimer,
              "Reverse Address Resolution Protocol", STD 38, RFC 903,
              June 1984.

   [RFC1931]  Brownell, D., "Dynamic RARP Extensions for Automatic
              Network Address Acquisition", RFC 1931, April 1996.

   [RFC2390]  Bradley, T., Brown, C., and A. Malis, "Inverse Address
              Resolution Protocol", RFC 2390, September 1998.

   [RFC3456]  Patel, B., Aboba, B., Kelly, S., and V. Gupta, "Dynamic
              Host Configuration Protocol (DHCPv4) Configuration of
              IPsec Tunnel Mode", RFC 3456, January 2003.

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Appendix A.  Changes from the Original RFCs

   This document specifies only the IANA rules associated with various
   fields in ARP.  The specification of these rules also affects the
   allocation of corresponding fields in protocols listed in Section 1
   that share the registry.  This document does not make any changes in
   the operation of these protocols themselves.

Authors' Addresses

   Jari Arkko
   Jorvas  02420

   EMail: jari.arkko@piuha.net

   Carlos Pignataro
   Cisco Systems
   7200-12 Kit Creek Road
   Research Triangle Park, NC  27709

   EMail: cpignata@cisco.com

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