Movatterモバイル変換

Network Working Group                                        S. KrishnanRequest for Comments: 5453                                      EricssonCategory: Standards Track                                  February 2009Reserved IPv6 Interface IdentifiersStatus 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 toBCP 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.Abstract   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.Krishnan                    Standards Track                     [Page 1]

RFC 5453          Reserved IPv6 Interface Identifiers      February 2009Table of Contents1. Introduction ....................................................21.1. Applicability ..............................................21.2. Requirements Notation ......................................32. Issues with Reusing Reserved Interface Identifiers ..............32.1. Possible Solutions .........................................33. IANA Considerations .............................................34. Acknowledgements ................................................45. Security Considerations .........................................46. References ......................................................56.1. Normative References .......................................56.2. Informative References .....................................5Appendix A. List of Potentially Affected RFCs ......................61.  Introduction   An IPv6 unicast address is composed of two parts: a subnet prefix and   an interface identifier (IID) that identifies a unique interface   within the subnet prefix.  The structure of an IPv6 unicast address   is depicted in "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 [RFC4291].  Examples of   mechanisms that generate interface identifiers without a 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 (Dynamic Host Configuration   Protocol for IPv6) [RFC3315].1.1.  Applicability   This document applies only to interface identifiers that are formed   in the modified EUI-64 format as defined inAppendix A of [RFC4291].   All other types of interface identifiers are out of its scope.Krishnan                    Standards Track                     [Page 2]

RFC 5453          Reserved IPv6 Interface Identifiers      February 20091.2.  Requirements Notation   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.  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:ffff.  This node will receive requests from all nodes   that are requesting a service from a Mobile IPv6 home agent since the   above-mentioned interface identifier has been reserved in [RFC2526]   to serve as a MIPv6 home agent's anycast address.  At best, this is   an annoyance to the node that came up with this address.  At worst,   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   autoconfiguration or for managed address configuration.2.1.  Possible Solutions   There are two possible ways to go about avoiding usage of these   reserved interface identifiers.  One of them would be to add a   normative reference to each specification that reserves an interface   identifier.  The other 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   because the number of such specifications that would 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.3.  IANA Considerations   This document creates an IANA registry for reserved IPv6 interface   identifiers.  Initial values for the reserved IPv6 interface   identifiers are given below.Krishnan                    Standards Track                     [Page 3]

RFC 5453          Reserved IPv6 Interface Identifiers      February 2009   +-----------------------------------------+-------------------------+   |        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: 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.4.  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, 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.5.  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].Krishnan                    Standards Track                     [Page 4]

RFC 5453          Reserved IPv6 Interface Identifiers      February 20096.  References6.1.  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 2008.6.2.  Informative References   [HBA]      Bagnulo, M.,"Hash Based Addresses (HBA)", Work in              Progress, October 2006.   [RFC3315]  Droms, R., Ed., 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.Krishnan                    Standards Track                     [Page 5]

RFC 5453          Reserved IPv6 Interface Identifiers      February 2009Appendix A.  List of Potentially Affected RFCs   Implementations of the following RFCs need to be aware of the   reserved interface identifier ranges when they allocate new   addresses.  Future revisions of these RFCs should ensure that this is   either already sufficiently clear or that the text is amended to take   this into account.   oRFC 2590 - Transmission of IPv6 Packets over Frame Relay Networks      Specification   oRFC 3315 - Dynamic Host Configuration Protocol for IPv6 (DHCPv6)   oRFC 3972 - Cryptographically Generated Addresses (CGA)   oRFC 4489 - A Method for Generating Link-Scoped IPv6 Multicast      Addresses   oRFC 4862 - IPv6 Stateless Address Autoconfiguration   oRFC 4941 - Privacy Extensions for Stateless Address      Autoconfiguration in IPv6   oRFC 4982 - Support for Multiple Hash Algorithms in      Cryptographically Generated Addresses (CGAs)   oRFC 5072 - IP Version 6 over PPPAuthor's Address   Suresh Krishnan   Ericsson   8400 Decarie Blvd.   Town of Mount Royal, QC   Canada   Phone: +1 514 345 7900 x42871   EMail: suresh.krishnan@ericsson.comKrishnan                    Standards Track                     [Page 6]