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Reserved IPv6 Interface Identifiers

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 5453.
Author Suresh Krishnan
Last updated 2019-01-03 (Latest revision 2008-12-03)
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state (None)
Document shepherd (None)
IESG IESG state RFC 5453 (Proposed Standard)
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Jari Arkko
Send notices to (None)
Network Working Group                                        S. Krishnan
Internet-Draft                                                  Ericsson
Intended status: Standards Track                        December 3, 2008
Expires: June 6, 2009

                  Reserved IPv6 Interface Identifiers

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on June 6, 2009.

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   Interface Identifiers in IPv6 unicast addresses are used to identify
   interfaces on a link.  They are required to be unique within a
   subnet.  Several RFCs have specified interface identifiers or
   identifier ranges that have a special meaning attached to them.  An
   IPv6 node autoconfiguring an interface identifier in these ranges
   will encounter unexpected consequences.  Since there is no
   centralized repository for such reserved identifiers, this document
   aims to create one.

Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Issues with reusing reserved Interface Identifiers . . . . . .  5
     3.1.  Possible solutions . . . . . . . . . . . . . . . . . . . .  5
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  List of potentially affected RFCs . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
   Intellectual Property and Copyright Statements . . . . . . . . . . 12

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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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2.  Introduction

   An IPv6 unicast address is composed of two parts : A subnet prefix
   and an interface identifier (IID) that identifies an unique interface
   within the subnet prefix.  The structure of an IPv6 unicast address
   is depicted in the IPv6 Addressing Architecture [RFC4291] and is
   replicated here for clarity.

   |          n bits               |           128-n bits            |
   |       subnet prefix           |           interface ID          |

                   Figure 1: IPv6 Unicast Address Format

   For all unicast addresses, except those that start with the binary
   value 000, Interface IDs are required to be 64 bits long and to be
   constructed in Modified EUI-64 format.  Examples of mechanisms that
   generate interface identifiers without an unique token include
   Cryptographically Generated Addresses [RFC3972], Privacy Addresses
   [RFC4941], Hash Based Addresses [HBA] etc.  Non-unique interface
   identifiers can also be allocated using managed address assignment
   mechanisms like DHCPv6 [RFC3315].

2.1.  Applicability

   This document applies only to interface identifiers that are formed
   in the modified EUI-64 format as defined in Appendix A of [RFC4291].
   All other types of interface identifiers are out of scope.

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3.  Issues with reusing reserved Interface Identifiers

   Let us assume a node comes up with an interface identifier that has
   been reserved for use in some other capacity. e.g.  An IPv6 node that
   uses temporary IPv6 addresses [RFC4941] comes up with an IID of fdff:
   ffff:ffff:fff .  This node will receive requests from all nodes that
   are requesting a service from a MobileIPv6 home agent since the above
   mentioned interface identifier has been reserved in [RFC2526] to
   serve as a MIPv6 home agents anycast address.  At best this is an
   annoyance to the node that came up with this address.  In the worst
   case scenario another node on the link would be denied service and
   may not look for other methods of acquiring a home agent.  Thus, such
   reserved interface identifiers MUST NOT be used for autonomous auto-
   configuration or for managed address configuration.

3.1.  Possible solutions

   There are two possible ways to go about avoiding usage of these
   reserved interface identifiers.  One of them would be to add
   normative reference to each specification that reserves an interface
   identifier.  The other one would be to create an IANA registry for
   such interface identifiers.  There are two disadvantages to the
   normative reference approach.  Firstly, this approach does not scale
   well.  This is because the number of such specifications that need to
   be updated is large.  Secondly, the maturity level of the document
   reserving the IID might be lower than the one prohibited from using
   it.  This will cause a downward reference problem.  Therefore the
   better solution is to create an IANA registry for this purpose.

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4.  IANA Considerations

   This document requests the creation of an IANA registry for reserved
   IPv6 Interface Identifiers.  Initial values for the reserved IPv6
   Interface Identifiers are given below.

   |        Interface Identifier Range       |       Description       |
   |           0000:0000:0000:0000           |  Subnet-Router Anycast  |
   |                                         |        [RFC4291]        |
   |                                         |                         |
   | FDFF:FFFF:FFFF:FF80-FDFF:FFFF:FFFF:FFFF | Reserved Subnet Anycast |
   |                                         |    Addresses[RFC2526]   |

                       Table 1: Current Assignments

   It is possible that implementations might predate a specific
   assignment from this registry and hence not be cognizant of the
   reserved nature of the interface identifier.  Hence, future
   assignments from this registry are discouraged.  Future assignments,
   if any, are to be made through Standards Action [RFC5226].
   Assignments consist of a single interface identifier or a range of
   interface identifiers.

   NOTE: Please note that the address :: (all zeros in the interface
   identifier field) is used as the unspecified address and ::/0 is used
   as a default route indicator, as specified in [RFC5156].  These uses
   do not conflict with the reserved interface identifiers defined here,
   since the reserved identifiers defined in this document are used for
   avoiding conflicts with stateless address autoconfiguration that
   utilizes a 64 bit prefix length.

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5.  Acknowledgements

   The author would like to thank Alain Durand, Alex Petrescu, Bernie
   Volz, Bob Hinden, Christian Huitema, Fred Templin, Jordi Palet
   Martinez, Pekka Savola, Remi Denis-Courmount, Tim Enos, Alex
   Petrescu, Ed Jankiewicz, Brian Carpenter, Alfred Hoenes, Jari Arkko,
   Pasi Eronen, Tim Polk, Lars Eggert, Derek Atkins and Robert Sparks
   for reviewing this document and suggesting changes.

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6.  Security Considerations

   By utilizing one of the reserved interface identifiers, an IPv6 node
   might receive requests that it is not authorized to receive.
   Information that creates or updates a registration in this registry
   needs to be authenticated and authorized by the IANA based on the
   instructions set forth by [RFC5226].

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7.  References

7.1.  Normative References

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

   [RFC2526]  Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast
              Addresses", RFC 2526, March 1999.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

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

7.2.  Informative References

   [HBA]      Bagnulo, M., "Hash Based Addresses (HBA)",
              draft-ietf-shim6-hba-05 (work in progress), October 2006.

   [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.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, September 2007.

   [RFC5156]  Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156,
              April 2008.

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Appendix A.  List of potentially affected RFCs

   The following RFCs that generate interface identifiers need to be
   updated if they wish to avoid conflicts with the reserved interface
   identifier ranges.

   o  RFC2590 - Transmission of IPv6 Packets over Frame Relay Networks

   o  RFC3315 - Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

   o  RFC3972 - Cryptographically Generated Addresses (CGA)

   o  RFC4489 - A Method for Generating Link-Scoped IPv6 Multicast

   o  RFC4862 - IPv6 Stateless Address Autoconfiguration

   o  RFC4941 - Privacy Extensions for Stateless Address
      Autoconfiguration in IPv6

   o  RFC5072 - IP Version 6 over PPP

   o  RFC4982 - Support for Multiple Hash Algorithms in CGAs

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Author's Address

   Suresh Krishnan
   8400 Decarie Blvd.
   Town of Mount Royal, QC

   Phone: +1 514 345 7900 x42871

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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
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   This document and the information contained herein are provided on an

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