RObust Header Compression (ROHC): A Compression Profile for IP
RFC 3843

Document Type RFC - Proposed Standard (June 2004; No errata)
Updated by RFC 4815
Last updated 2013-03-02
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Network Working Group                                       L-E. Jonsson
Request for Comments: 3843                                  G. Pelletier
Category: Standards Track                                       Ericsson
                                                               June 2004

    RObust Header Compression (ROHC): A Compression Profile for IP

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 (2004).

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 (Encapsulating Security Payload),
   IP/UDP, and also a profile for uncompressed packet streams.  However,
   no profile was defined for compression of IP only, which has been
   identified as a missing piece in RFC 3095.  This document defines a
   ROHC compression profile for IP, similar to the IP/UDP profile
   defined by RFC 3095, but simplified to exclude UDP, and enhanced to
   compress IP header chains of arbitrary length.

   Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .  2
   3.  ROHC IP Compression (Profile 0x0004) . . . . . . . . . . . . .  3
       3.1.  Static Chain Termination . . . . . . . . . . . . . . . .  3
       3.2.  Handling Multiple Levels of IP Headers . . . . . . . . .  3
       3.3.  Constant IP-ID . . . . . . . . . . . . . . . . . . . . .  4
       3.4.  Additional Mode Transition Logic . . . . . . . . . . . .  6
       3.5.  Initialization . . . . . . . . . . . . . . . . . . . . .  8
       3.6.  Packet Types . . . . . . . . . . . . . . . . . . . . . .  8
       3.7.  The CONTEXT_MEMORY Feedback Option . . . . . . . . . . . 10
   4.  Security Considerations. . . . . . . . . . . . . . . . . . . . 10
   5.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 10
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 11

Jonsson & Pelletier         Standards Track                     [Page 1]
RFC 3843                 A ROHC Profile for IP                 June 2004

   Appendix A.  Detailed Procedures for Canceling Mode Transitions. . 12
       A.1.  Transition from Optimistic to Reliable Mode. . . . . . . 12
       A.2.  Transition from Unidirectional to Reliable Mode. . . . . 13
       A.3.  Transition from Reliable to Optimistic Mode. . . . . . . 13
       A.4.  Transition Back to Unidirectional Mode . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 16

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 (Encapsulating Security Payload),
   IP/UDP, and also a profile for uncompressed packet streams.  The
   profile for uncompressed data was defined to provide a 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 not yet 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-2460] packets, and that
   the IP header often represents 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-2460] 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.  The most important differences are a different
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