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Versions: (draft-jonsson-rohc-ip-only) 00 01 02 03 04 05 RFC 3843

Network Working Group                                       L-E. Jonsson
INTERNET-DRAFT                                                  Ericsson
Expires: April 2003                                     October 28, 2002






                    RObust Header Compression (ROHC):
                       A Compression Profile for IP
                     <draft-ietf-rohc-ip-only-00.txt>


Status of this memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   This document is a submission of the IETF ROHC WG. Comments should be
   directed to the ROHC WG mailing list, rohc@ietf.org.


Abstract

   The original RObust Header Compression (ROHC) RFC, RFC 3095, defines
   a framework for header compression, along with compression protocols
   (profiles) for IP/UDP/RTP, IP/ESP, IP/UDP, and also for uncompressed
   packet streams. However, no profile was defined for compression of IP
   only, which has been identified as a flaw in RFC 3095. This document
   addresses that problem and defines a ROHC compression profile for IP,
   similar to the IP/UDP profile defined by RFC 3095, but simplified to
   exclude UDP.





Jonsson                                                         [Page 1]


INTERNET-DRAFT      A ROHC Compression Profile for IP   October 28, 2002


Table of Contents

   1.  Introduction..................................................2
   2.  Terminology...................................................2
   3.  ROHC IP Compression (Profile 0x0004)..........................3
   4.  Security Considerations.......................................4
   5.  IANA Considerations...........................................4
   6.  References....................................................4
   7.  Author's Address..............................................4

1.  Introduction

   The original RObust Header Compression (ROHC) RFC [RFC-3095] defines
   a framework for header compression, along with compression protocols
   (profiles) for IP/UDP/RTP, IP/ESP, IP/UDP, and also for uncompressed
   packet streams. The profile for uncompressed data was defined to
   provide means to encapsulate all traffic over a link within ROHC
   packets. Through this profile, the lower layers do not have to
   provide multiplexing for different packet types, but instead ROHC can
   handle any packet stream, even if compression profiles for all kinds
   of packet streams have yet not been defined or implemented over the
   link.

   Although the profile without compression is simple and can tunnel
   arbitrary packets, it has of course a major weakness in that it does
   not compress the headers at all. When considering that normally all
   packets are expected to be IP [RFC-791, RFC-1883] packets, and that
   the IP header often represent a major part of the total header, a
   useful alternative to no compression would for most packets be
   compression of the IP header only. Unfortunately, such a profile was
   not defined in [RFC-3095], and this has thus been identified as an
   important missing piece in the ROHC toolbox.

   This document addresses this missing compression support and defines
   a ROHC compression profile for IP [RFC-791, RFC-1883] only, similar
   to the IP/UDP profile defined by [RFC-3095], but simplified to
   exclude UDP. Due to the similarities with the IP/UDP profile, the IP
   compression profile is described based on the IP/UDP profile, mainly
   covering differences.

2.  Terminology

   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 RFC 2119 [RFC-2119].

   ROHC UDP

       "ROHC UDP" in this document refers to the IP/UDP profile
       (Profile 0x0002) as defined in [RFC-3095].




Jonsson                                                         [Page 2]


INTERNET-DRAFT      A ROHC Compression Profile for IP   October 28, 2002


3.  ROHC IP Compression (Profile 0x0004)

   In principle, there is no real difference between the ROHC UDP
   profile and the IP profile defined in this document, since the
   removal of UDP does not at all effect the compression mechanisms. As
   for ROHC UDP, the compressor generates a 16-bit sequence number which
   increases by one for each packet compressed in the packet stream,
   called SN or IP SN below. Unless stated explicitly below, mechanisms
   and formats are as for ROHC UDP.

3.1.  Initialization

   The static context for ROHC IP compression can be initialized in
   either of two ways:

   1) By using an IR packet as in ROHC UDP, where the profile is
      0x0004 and the static chain ends with the static part of an
      IP header.

   *********************************************************************
   *  Note: An open issue is how to terminate the static chain. Any    *
   *        NextHdr/Protocol other than 4 (IPinIP) or 41 (IPv6) would  *
   *        terminate the chain, but so would also a third IP header.  *
   *********************************************************************

      At the compressor, IP SN is initialized to a random
      value when the IR packet is sent.

   2) By reusing an existing context where the existing static chain
      contains the static part of an IP header.

   *********************************************************************
   *  Note: This will have to be revised based on what is decided for  *
   *        the above issue.                                           *
   *********************************************************************

      As for ROHC UDP, this is done with an IR-DYN packet, identifying
      profile 0x0004, where the dynamic chain corresponds to the prefix
      of the existing static chain that ends with the IP header.

   *********************************************************************
   *  Note: This will have to be revised based on what is decided for  *
   *        the above issue.                                           *
   *********************************************************************

      At the compressor, IP SN is initialized to a random value.

   For ROHC IP, the dynamic part of a compressed packet is similar to
   the one for ROHC UDP, with a two-octet field containing the SN added
   to the end of the chain. This affects the format of dynamic chains in
   IR and IR-DYN packets.



Jonsson                                                         [Page 3]


INTERNET-DRAFT      A ROHC Compression Profile for IP   October 28, 2002



4.  Security Considerations

   The security considerations of [RFC-3095] apply equally to this
   document, without exceptions or additions.

5.  IANA Considerations

   ROHC profile identifier 0x0004 has been reserved by the IANA for the
   profile defined in this document.

   [TO BE REMOVED BEFORE PUBLICATION]
      A ROHC profile identifier must be reserved by the IANA for the
      profile defined in this document. Profile number 0x0004 has
      previously been saved for this purpose, and should thus be used.
      As for previous ROHC profiles, profile numbers 0xnnXX must also be
      reserved for future updates of this profile. A suggested
      registration in the "RObust Header Compression (ROHC) Profile
      Identifiers" name space would then be:

      0x0004               ROHC IP                    [RFCXXXX (this)]
      0xnn04               Reserved
   [END]

6.  References

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

   [RFC-3095]  Bormann, C., Burmeister, C., Degermark, M., Fukushima,
               H., Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T.,
               Le, K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro,
               K., Wiebke, T., Yoshimura, T. and H. Zheng, "Robust
               Header Compression (ROHC)", RFC 3095, July 2001.

   [RFC-791]   Postel, J., "Internet Protocol", RFC 791, September 1981.

   [RFC-1883]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
               (IPv6) Specification", RFC 1883, December 1995.

7.  Author's Address

   Lars-Erik Jonsson              Tel: +46 920 20 21 07
   Ericsson AB                    Fax: +46 920 20 20 99
   Box 920
   SE-971 28 Lulea
   Sweden                         EMail: lars-erik.jonsson@ericsson.com







Jonsson                                                         [Page 4]


INTERNET-DRAFT      A ROHC Compression Profile for IP   October 28, 2002


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This Internet-Draft expires April 28, 2003.



















Jonsson                                                         [Page 5]


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