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RObust Header Compression (ROHC): A Link-Layer Assisted Profile for IP/UDP/RTP
RFC 4362

Document type: RFC - Proposed Standard (January 2006)
Updated by RFC 4815
Obsoletes RFC 3242
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4362 (Proposed Standard)
Responsible AD: Allison Mankin
Send notices to: cabo@tzi.org, lars-erik.jonsson@ericsson.com

Network Working Group                                       L-E. Jonsson
Request for Comments: 4362                                  G. Pelletier
Obsoletes: 3242                                              K. Sandlund
Category: Standards Track                                       Ericsson
                                                            January 2006

                   RObust Header Compression (ROHC):
              A Link-Layer Assisted Profile for IP/UDP/RTP

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 (2006).

Abstract

   This document defines a ROHC (Robust Header Compression) profile for
   compression of IP/UDP/RTP (Internet Protocol/User Datagram
   Protocol/Real-Time Transport Protocol) packets, utilizing
   functionality provided by the lower layers to increase compression
   efficiency by completely eliminating the header for most packets
   during optimal operation.  The profile is built as an extension to
   the ROHC RTP profile.  It defines additional mechanisms needed in
   ROHC, states requirements on the assisting layer to guarantee
   transparency, and specifies general logic for compression and
   decompression related to the usage of the header-free packet format.
   This document is a replacement for RFC 3242, which it obsoletes.

Jonsson, et al.             Standards Track                     [Page 1]
RFC 4362             A Link-Layer Assisted ROHC RTP         January 2006

Table of Contents

   1. Introduction ....................................................2
      1.1. Differences from RFC 3242 ..................................5
   2. Terminology .....................................................5
   3. Overview of the Link-Layer Assisted Profile .....................6
      3.1. Providing Packet Type Identification .......................7
      3.2. Replacing the Sequence Number ..............................7
      3.3. CRC Replacement ............................................8
      3.4. Applicability of This Profile ..............................8
   4. Additions and Exceptions Compared to ROHC RTP ...................9
      4.1. Additional Packet Types ....................................9
           4.1.1. No-Header Packet (NHP) ..............................9
           4.1.2. Context Synchronization Packet (CSP) ................9
           4.1.3. Context Check Packet (CCP) .........................11
      4.2. Interfaces Towards the Assisting Layer ....................12
           4.2.1. Interface, Compressor to Assisting Layer ...........13
           4.2.2. Interface, Assisting Layer to Decompressor .........13
      4.3. Optimistic Approach Agreement .............................14
      4.4. Fast Context Initialization, IR Redefinition ..............15
      4.5. Feedback Option, CV-REQUEST ...............................16
      4.6. Periodic Context Verification .............................16
      4.7. Use of Context Identifier .................................16
   5. Implementation Issues ..........................................17
      5.1. Implementation Parameters and Signals .....................17
           5.1.1. Implementation Parameters at the Compressor ........17
           5.1.2. Implementation Parameters at the Decompressor ......19
      5.2. Implementation over Various Link Technologies .............19
   6. IANA Considerations ............................................20
   7. Security Considerations ........................................20
   8. Acknowledgements ...............................................20
   9. References .....................................................20
      9.1. Normative References ......................................20
      9.2. Informative References ....................................21

1.  Introduction

   Header compression is a technique used to compress and transparently
   decompress the header information of a packet on a per-hop basis,
   utilizing redundancy within individual packets and between
   consecutive packets within a packet stream.  Over the years, several
   protocols [VJHC, IPHC] have been developed to compress the network
   and transport protocol headers [IPv4, IPv6, UDP, TCP], and these
   schemes have been successful in improving efficiency over many wired
   bottleneck links, such as modem connections over telephone networks.
   In addition to IP, UDP, and TCP compression, an additional

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