    Network Working Group                                         M. Bagnulo
    Request for Comments: 4581                                          UC3M
    Updates: 3972                                                   J. Arkko
    Category: Standards Track                                       Ericsson
                                                                October 2006

       Cryptographically Generated Addresses (CGA) Extension Field Format

    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) The Internet Society (2006).

    Abstract

       This document defines a Type-Length-Value format for
       Cryptographically Generated Address (CGA) Extensions.  This document
       updates RFC 3972.

    Table of Contents

       1. Introduction ....................................................2
       2. CGA Extension Field Format ......................................2
       3. IANA Considerations .............................................2
       4. Security Considerations .........................................3
       5. Acknowledgements ................................................3
       6. Normative References ............................................3

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    RFC 4581               CGA Extension Field Format           October 2006

    1.  Introduction

       The Cryptographically Generated Address (CGA) specification [1]
       defines Extension Fields that allow additional information to be
       included in the CGA Parameter Data Structure.  So far there seems to
       be enough interest in including additional data items into the CGA
       Parameter Data Structure through these Extension Fields that it seems
       reasonable to expect that more than one mechanism will require its
       usage.  In order to simplify the addition of multiple data items,
       this document updates RFC 3972 [1], and it defines a Type-Length-
       Value format for the Extension Fields.

    2.  CGA Extension Field Format

       Data items to be included in Extension Fields of the CGA Parameter
       Data Structure MUST be encoded using the following Type-Length-Value
       (TLV) format:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Extension Type        |   Extension Data Length       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~                       Extension Data                          ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Extension Type: 16-bit identifier of the type of the Extension Field.

       Extension Data Length: 16-bit unsigned integer.  Length of the
       Extension Data field of this option, in octets.

       Extension Data: Variable-length field.  Extension-Type-specific data.

    3.  IANA Considerations

       The IANA has created and will maintain a registry entitled, "CGA
       Extension Type".  The values in this name space are 16-bit unsigned
       integers.  Initial values for the CGA Extension Type field are given
       below; future assignments are to be made through Standards Action
       [2].  Assignments consist of a name and the value.

       As recommended in [3], this document makes the following assignments
       for experimental and testing use: the value 0xFFFD, with name
       Exp_FFFD; the value 0xFFFE, with name Exp_FFFE, and the value 0xFFFF,
       with name Exp_FFFF.

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    RFC 4581               CGA Extension Field Format           October 2006

    4.  Security Considerations

       No security concerns are raised by the adoption of the CGA Extension
       format described in this document.  However, proper security analysis
       is required when new CGA Extensions are defined in order to make sure
       that they introduce no new vulnerabilities to the existing CGA
       schemes.

    5.  Acknowledgements

       Comments to this document were provided by Sam Hartman, Allison
       Mankin, Pekka Savola, Thomas Narten, Tuomas Aura, Stefan Rommer,
       Julien Laganier, and James Kempf.

    6.  Normative References

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

       [2]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
            Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

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

    Authors' Addresses

       Marcelo Bagnulo
       Universidad Carlos III de Madrid
       Av. Universidad 30
       Leganes, Madrid  28911
       SPAIN

       Phone: 34 91 6249500
       EMail: marcelo@it.uc3m.es
       URI:   http://www.it.uc3m.es

       Jari Arkko
       Ericsson
       Jorvas  02420
       Finland

       EMail: jari.arkko@ericsson.com

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    RFC 4581               CGA Extension Field Format           October 2006

    Full Copyright Statement

       Copyright (C) The Internet Society (2006).

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