RObust Header Compression (ROHC): A Link-Layer Assisted Profile for IP/UDP/RTP
RFC 3242
| Document | Type |
RFC - Proposed Standard
(April 2002; No errata)
Obsoleted by RFC 4362
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| This information refers to IESG processing after the RFC was initially published: | |||
| IESG | IESG state | RFC 3242 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| IESG note | Responsible: Finished | ||
| Send notices to | <cabo@tzi.org>, <lars-erik.jonsson@ericsson.com> | ||
Network Working Group L-E. Jonsson
Request for Comments: 3242 G. Pelletier
Category: Standards Track Ericsson
April 2002
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 (2002). All Rights Reserved.
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 making use of this header-free packet.
Table of Contents
1. Introduction....................................................2
2. Terminology.....................................................4
3. Overview of the Link-Layer Assisted Profile.....................5
3.1. Providing Packet Type Identification.....................6
3.2. Replacing the Sequence Number............................6
3.3. CRC Replacement..........................................7
3.4. Applicability of This Profile............................7
4. Additions and Exceptions Compared to ROHC RTP...................8
4.1. Additional Packet Types..................................8
4.1.1. No-Header Packet (NHP)..........................8
4.1.2. Context Synchronization Packet (CSP)............8
4.1.3. Context Check Packet (CCP)......................9
Jonsson, et. al Standards Track [Page 1]
RFC 3242 A Link-Layer Assisted ROHC RTP April 2002
4.2. Interfaces Towards the Assisting Layer..................11
4.2.1. Interface, Compressor to Assisting Layer.......11
4.2.2. Interface, Assisting Layer to Decompressor.....12
4.3. Optimistic Approach Agreement...........................13
4.4. Fast Context Initialization, IR Redefinition............13
4.5. Feedback Option, CV-REQUEST.............................14
4.6. Periodic Context Verification...........................15
4.7. Use of Context Identifier...............................15
5. Implementation Issues..........................................15
5.1. Implementation Parameters and Signals...................15
5.1.1. Implementation Parameters at the Compressor....16
5.1.2. Implementation Parameters at the Decompressor..17
5.2. Implementation over Various Link Technologies...........18
6. IANA Considerations............................................18
7. Security Considerations........................................18
8. Acknowledgements...............................................18
9. References.....................................................19
10. Authors' Addresses.............................................20
11. Full Copyright Statement.......................................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
compression scheme called Compressed RTP [CRTP] has been developed to
further improve compression efficiency for the case of real-time
traffic using the Real-Time Transport Protocol [RTP].
The schemes mentioned above have all been designed taking into
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