RObust Header Compression (ROHC): Requirements on TCP/IP Header Compression
RFC 4163

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Network Working Group                                       L-E. Jonsson
Request for Comments: 4163                                      Ericsson
Category: Informational                                      August 2005

                   RObust Header Compression (ROHC):
               Requirements on TCP/IP Header Compression

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document contains requirements on the TCP/IP header compression
   scheme (profile) to be developed by the RObust Header Compression
   (ROHC) Working Group.  The document discusses the scope of TCP
   compression, performance considerations, assumptions about the
   surrounding environment, as well as Intellectual Property Rights
   concerns.  The structure of this document is inherited from RFC 3096,
   which defines IP/UDP/RTP requirements for ROHC.

Table of Contents

   1. Introduction ....................................................2
   2. Header Compression Requirements .................................2
      2.1. Impact on Internet Infrastructure ..........................2
      2.2. Supported Headers and Kinds of TCP Streams .................3
      2.3. Performance Issues .........................................4
      2.4. Requirements Related to Link Layer Characteristics .........6
      2.5. Intellectual Property Rights (IPR) .........................7
   3. Security Consideration ..........................................7
   4. IANA Considerations .............................................7
   5. Acknowledgements ................................................7
   6. Informative References ..........................................7

Jonsson                      Informational                      [Page 1]
RFC 4163              Requirements on ROHC TCP/IP            August 2005

1.  Introduction

   The goal of the ROHC WG is to develop header compression schemes that
   perform well over links with high error rates and long link roundtrip
   times.  The schemes must perform well for cellular links that use
   technologies such as Wideband Code Division Multiple Access (W-CDMA),
   Enhanced Data rates for GSM Evolution (EDGE), and CDMA2000.  However,
   the schemes should also be applicable to other link technologies with
   high loss and long roundtrip times.

   The main objective for ROHC has been robust compression of IP/UDP/RTP
   [5], but the WG is also chartered to develop new header compression
   solutions for IP/TCP [1], [2].  Because TCP traffic, in contrast to
   RTP, has usually been sent over reliable links, existing schemes for
   TCP, [3] and [4], have not experienced the same robustness problems
   as RTP compression.  However, there are still many scenarios where
   TCP header compression will be implemented over less reliable links
   [11], [12], making robustness an important objective for the new TCP
   compression scheme.  Other, equally important, objectives for ROHC
   TCP compression are: improved compression efficiency, enhanced
   capabilities for compression of header fields including TCP options,
   and finally incorporation of TCP compression into the ROHC framework
   [6].

2.  Header Compression Requirements

   The following requirements have, more or less arbitrarily, been
   divided into five groups.  The first group deals with requirements
   concerning the impact of a header compression scheme on the rest of
   the Internet infrastructure.  The second group defines what kind of
   headers must be compressed efficiently.  The third and fourth groups
   concern performance requirements and capability requirements that
   stem from the properties of link technologies where ROHC TCP is
   expected to be used.  Finally, the fifth section discusses
   Intellectual Property Rights related to ROHC TCP compression.

2.1.  Impact on Internet Infrastructure

   1.  Transparency: When a header is compressed and then decompressed,
       the resulting header must be semantically identical to the
       original header.  If this cannot be achieved, the packet
       containing the erroneous header must be discarded.

       Justification: The header compression process must not produce
       headers that might cause problems for any current or future part
       of the Internet infrastructure.

Jonsson                      Informational                      [Page 2]
RFC 4163              Requirements on ROHC TCP/IP            August 2005

       Note: The ROHC WG has not found a case where "semantically
       identical" is not the same as "bitwise identical".

   2.  Ubiquity: Must not require modifications to existing IP (v4 or
       v6) or TCP implementations.

       Justification: Ease of deployment.

       Note: The ROHC WG may recommend changes that would increase the