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
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.
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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