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Versions: 00 01 02 03 04 05 06 RFC 6564

6man Working Group                                           S. Krishnan
Internet-Draft                                                  Ericsson
Intended status: Standards Track                           j h. woodyatt
Expires: June 20, 2011                                             Apple
                                                                E. Kline
                                                                  Google
                                                             J. Hoagland
                                                                Symantec
                                                               M. Bhatia
                                                          Alcatel-Lucent
                                                       December 17, 2010


              An uniform format for IPv6 extension headers
                       draft-ietf-6man-exthdr-01

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 defines a format for defining a new
   family of IPv6 extension headers.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 20, 2011.

Copyright Notice

   Copyright (c) 2010 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



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   (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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Conventions used in this document . . . . . . . . . . . . . 3
   2.  Generic IPv6 Extension Header (GIEH) format . . . . . . . . . . 4
   3.  Backward Compatibility  . . . . . . . . . . . . . . . . . . . . 6
   4.  Exceptions  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Future work . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   9.  Normative References  . . . . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7





























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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,
   some intermediate nodes such as firewalls, may need to look at the
   transport layer header fields in order to make a decision to allow or
   deny the packet.  If new extension headers are defined and the
   intermediate node is not aware of them, the intermediate node cannot
   proceed further in the header chain since it does not know where the
   unknown header ends and the next header begins.  The main issue is
   that the extension header format is not standardized and hence it is
   not possible to skip past the unknown header.  This document defines
   a standard format for a new family of IPv6 extension headers.

1.1.  Conventions used in this document

   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.  Generic IPv6 Extension Header (GIEH) format

   This document proposes a new family of IPv6 extension headers that
   will be encoded in a consistent format so that it is possible for
   intermediate nodes to skip over unknown extension headers and
   continue to further process the header chain if they so desire.  The
   intention of the base IPv6 Specification [RFC2460] that destination
   hosts not be permitted to skip unknown extension headers continues to
   apply.  One key advantage of using such a generic IPv6 extension
   header is that it allows nodes to distinguish between unknown
   extension headers and unknown upper layer protocols, which was not
   possible earlier.  Another one is that this generic extension header
   conserves values in the IPv4 protocol numbers registry.

   This documents requires the allocation of a single IP protocol number
   for the Generic IPv6 extension header (GIEH), say TBA1.
   Specifications of new extension headers SHOULD use this generic
   extension header format whenever feasible.  The generic extension
   header will be identified by the value TBA1 occuring in the Next
   Header field of the preceding extension header.  The second octet
   contains the length of the extension header.  The third octet of the
   GIEH contains a specific extension header type (that identifies the
   actual extension header).  All other data in the GIEH is type-
   specific.

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Next Header  |  Hdr Ext Len  | Specific Type |  Hdr Options  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                                               |
  .                                                               .
  .                  Header Specific Data                         .
  .                                                               .
  |                                                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Next Header          8-bit selector. Identifies the type of header
                       immediately following this Extension header.
                       Uses the same values as the IPv4 Protocol
                       field.

  Hdr Ext Len          8-bit unsigned integer.  Length of the
                       Extension header in 8-octet units, not
                       including the first 8 octets.

  Specific Type        8-bit unsigned integer. The actual IPv6
                       extension header type. This will be allocated



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                       from a new IANA registry.

  Hdr Options          8-bit selector. The two most significant bits
                       specify the action that must be taken if the
                       processing IPv6 node does not recognize the
                       extension header:

                       00 - skip over this option and continue
                            processing the header.

                       01 - discard the packet.

                       10 - discard the packet and, regardless of
                            whether or not the packet's Destination
                            Address was a multicast address, send
                            an ICMP Parameter Problem, Code 1, message
                            to the packet's Source Address, pointing to
                            the unrecognized value within  the original
                            packet.

                       11 - discard the packet and, only if the packet's
                            Destination Address was not a multicast
                            address, send an ICMP parameter Problem,
                            Code 1, message to the packet's Source
                            Address, pointing to the unrecognized value
                            within the original packet.

                       The other 6 bits in this field are reserved. They
                       MUST be set to zero on transmission and SHOULD be
                       ignored on reception.

  Header Specific      Variable length. Fields specific to the
  Data                 extension header. This field MUST be padded
                       as required in order to ensure that the
                       complete GIEH is a multiple of 8 octets long.

           Figure 1: Generic IPv6 Extension Header (GIEH) layout














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3.  Backward Compatibility

   The scheme proposed in this document is not backward compatible with
   all the currently defined IPv6 extension headers.  It only applies to
   newly defined extension headers.  Specifically, the following
   extension headers predate this document and do not follow the format
   proposed in this document.

   o  IPv6 Hop-by-Hop Options Header
   o  IPv6 Routing Header
   o  IPv6 Fragment Header
   o  IPv6 Destination Options Header


4.  Exceptions

   The the Generic IPv6 extension header is generic enough that it is
   suitable to use for most applications.  However, it is possible that
   the GIEH does not satisfy the requirements in all cases where new
   extension headers are required.  Hence, the existence of this generic
   header does not necessarily preclude the definition of new
   independent IPv6 extension headers.


5.  Future work

   This document proposes one step in easing the inspection of extension
   headers by middleboxes.  There is further work required in this area.
   Some issues that are left unresolved beyond this document include

   o  There can be an arbitrary number of extension headers.
   o  Extension headers must be processed in the order they appear.
   o  Extension headers may alter the processing of the payload itself,
      and hence the packet may not be processed properly without
      knowledge of said header.


6.  IANA Considerations

   This document requests a single allocation from the IANA for this
   generic IPv6 extension header type (TBA1) from the Assigned Internet
   Protocol Numbers registry located at
   http://www.iana.org/assignments/protocol-numbers.

   This document also requests the creation of a new registry for GIEH
   sub-types.  The allocation policy for these subtypes is Standards
   Action.




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7.  Security Considerations

   This document proposes a standard format for the IPv6 extension
   headers so that intermediate nodes that do not understand the
   contents of these headers can look past them.  Intermediate nodes,
   such as firewalls, skipping over unknown headers might end up
   allowing the setup of a covert channel from the outside of the
   firewall to the inside using the data field(s) of the unknown
   extension headers.


8.  Acknowledgements

   The authors would like to thank Albert Manfredi, Bob Hinden, Brian
   Carpenter, Erik Nordmark, Hemant Singh, Lars Westberg, Markku Savela,
   Tatuya Jinmei, Thomas Narten, Vishwas Manral, Alfred Hoenes, Joel
   Halpern and Ran Atkinson for their reviews and suggestions that made
   this document better.


9.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.


Authors' Addresses

   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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   james woodyatt
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014
   US

   Email: jhw@apple.com


   Erik Kline
   Google
   604 Arizona Avenue
   Santa Monica, CA  90401
   US

   Phone: +1 310 460 4080
   Email: ek@google.com


   James Hoagland
   Symantec Corporation
   350 Ellis St.
   Mountain View, CA  94043
   US

   Email: Jim_Hoagland@symantec.com
   URI:   http://symantec.com/


   Manav Bhatia
   Alcatel-Lucent
   Bangalore
   India

   Email: manav.bhatia@alcatel-lucent.com
















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