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A Uniform Format for IPv6 Extension Headers
RFC 6564

Internet Engineering Task Force (IETF)                       S. Krishnan
Request for Comments: 6564                                      Ericsson
Updates: 2460                                                J. Woodyatt
Category: Standards Track                                          Apple
ISSN: 2070-1721                                                 E. Kline
                                                                  Google
                                                             J. Hoagland
                                                                Symantec
                                                               M. Bhatia
                                                          Alcatel-Lucent
                                                              April 2012

              A Uniform Format for IPv6 Extension Headers

Abstract

   In IPv6, optional internet-layer information is encoded in separate
   headers that may be placed between the IPv6 header and the transport-
   layer header.  There are a small number of such extension headers
   currently defined.  This document describes the issues that can arise
   when defining new extension headers and discusses the alternate
   extension mechanisms in IPv6.  It also provides a common format for
   defining any new IPv6 extension headers, if they are needed.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6564.

Krishnan, et al.             Standards Track                    [Page 1]
RFC 6564            Format for IPv6 Extension Headers         April 2012

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................3
   3. Applicability ...................................................3
   4. Proposed IPv6 Extension Header Format ...........................4
   5. Backward Compatibility ..........................................4
   6. Future Work .....................................................5
   7. Security Considerations .........................................5
   8. Acknowledgements ................................................5
   9. Normative References ............................................5

1.  Introduction

   The base IPv6 standard [RFC2460] defines extension headers as an
   expansion mechanism to carry optional internet-layer information.
   Extension headers, with the exception of the Hop-by-Hop Options
   header, are not usually processed on intermediate nodes.  However,
   several existing deployed IPv6 routers and several existing deployed
   IPv6 firewalls, in contradiction to [RFC2460], are capable of parsing
   past or ignoring all currently defined IPv6 extension headers (e.g.,
   to examine transport-layer header fields) at wire speed (e.g., by
   using custom Application-specific Integrated Circuits (ASICs) for
   packet processing).  Hence, one must also consider that any new IPv6
   extension header will break IPv6 deployments that use these existing
   capabilities.

   Any IPv6 header or option that has hop-by-hop behavior, and is
   intended for general use in the public IPv6 Internet, could be
   subverted to create an attack on IPv6 routers that process packets
   containing such a header or option.  Reports from the field indicate
   that some IP routers deployed within the global Internet are
   configured either to ignore the presence of headers with hop-by-hop

Krishnan, et al.             Standards Track                    [Page 2]
RFC 6564            Format for IPv6 Extension Headers         April 2012

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