





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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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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Full Copyright Statement

   Copyright (C) The Internet Society (2006).

   This document is subject to the rights, licenses and restrictions
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Acknowledgement

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   Administrative Support Activity (IASA).







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