RObust Header Compression (ROHC): Context Replication for ROHC Profiles
RFC 4164

Document Type RFC - Proposed Standard (September 2005; No errata)
Last updated 2013-03-02
Stream IETF
Formats plain text pdf html
Stream WG state (None)
Consensus Unknown
Document shepherd No shepherd assigned
IESG IESG state RFC 4164 (Proposed Standard)
Telechat date
Responsible AD Allison Mankin
Send notices to cabo@tzi.org, lars-erik.jonsson@ericsson.com
Network Working Group                                       G. Pelletier
Request for Comments: 4164                                      Ericsson
Category: Standards Track                                    August 2005

                   RObust Header Compression (ROHC):
                 Context Replication for ROHC Profiles

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 (2005).

Abstract

   This document defines context replication, a complement to the
   context initialization procedure found in Robust Header Compression
   (ROHC), as specified in RFC 3095.  Profiles defining support for
   context replication may use the mechanism described herein to
   establish a new context based on another already existing context.
   Context replication is introduced to reduce the overhead of the
   context establishment procedure.  It may be especially useful for the
   compression of multiple short-lived flows that may be occurring
   simultaneously or near-simultaneously, such as short-lived TCP flows.

Pelletier                   Standards Track                     [Page 1]
RFC 4164         Context Replication for ROHC Profiles       August 2005

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Context Replication for ROHC Profiles ...........................5
      3.1. Robustness Considerations ..................................5
      3.2. Replication of Control Fields ..............................5
      3.3. Compressor States and Logic ................................6
           3.3.1. Context Replication (CR) State ......................6
           3.3.2. State Machine with Context Replication ..............7
           3.3.3. State Transition Logic ..............................7
                  3.3.3.1. Selection of Base Context, Upward
                           Transition .................................8
                  3.3.3.2. Optimistic Approach, Upward Transition .....9
                  3.3.3.3. Optional Acknowledgements (ACKs),
                           Upward Transition ..........................9
                  3.3.3.4. Negative ACKs (NACKs), Downward
                           Transition .................................9
      3.4. Decompressor Logic ........................................10
           3.4.1. Replication and Context Initialization .............10
           3.4.2. Reconstruction and Verification ....................10
           3.4.3. Actions upon Failure ...............................11
           3.4.4. Feedback Logic .....................................11
      3.5. Packet Formats ............................................11
           3.5.1. CRCs in the IR-CR Packet ...........................12
                  3.5.1.1. 7-bit CRC .................................13
                  3.5.1.2. 8-bit CRC .................................13
           3.5.2. General Format of the IR-CR Packet .................13
           3.5.3. Properties of the Base Context Identifier (BCID) ...15
   4. Security Considerations ........................................15
   5. Acknowledgements ...............................................15
   6. References .....................................................16
      6.1. Normative References ......................................16
      6.2. Informative References ....................................16
   Appendix A: General Format of the IR-CR Packet (Informative).......17
      A.1.  General Structure (Informative) ..........................17
      A.2.  Profile-Specific Replication Information (Informative) ...17
   Appendix B: Inter-Profile Context Replication (Informative)........18
      B.1.  Defining Support for Inter-Profile Context Replication ...18
      B.2.  Compatibility between Different Profiles (Informative) ...19

Pelletier                   Standards Track                     [Page 2]
RFC 4164         Context Replication for ROHC Profiles       August 2005

1.  Introduction

   There is often some redundancy between header fields of different
   flows that pass through the same compressor-decompressor pair.  This
   means that some of the information needed to initialize the context
   for decompressing the headers of a new flow may already be present at
   the decompressor.  It may be desirable to reuse this information and
Show full document text