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Versions: 00 01 02 03 RFC 5453
Network Working Group S. Krishnan
Internet-Draft Ericsson
Intended status: Standards Track December 3, 2008
Expires: June 6, 2009
Reserved IPv6 Interface Identifiers
draft-ietf-6man-reserved-iids-03
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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.
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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
Addresses
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
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com
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