The RObust Header Compression (ROHC) Framework
RFC 4995
| Document | Type |
RFC - Proposed Standard
(July 2007; Errata)
Obsoleted by RFC 5795
|
|
|---|---|---|---|
| Last updated | 2018-12-20 | ||
| Stream | IETF | ||
| Formats | plain text pdf htmlized with errata bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4995 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Magnus Westerlund | ||
| Send notices to | (None) | ||
Network Working Group L-E. Jonsson
Request for Comments: 4995 G. Pelletier
Category: Standards Track K. Sandlund
Ericsson
July 2007
The RObust Header Compression (ROHC) Framework
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 IETF Trust (2007).
Abstract
The Robust Header Compression (ROHC) protocol provides an efficient,
flexible, and future-proof header compression concept. It is
designed to operate efficiently and robustly over various link
technologies with different characteristics.
The ROHC framework, along with a set of compression profiles, was
initially defined in RFC 3095. To improve and simplify the ROHC
specifications, this document explicitly defines the ROHC framework
and the profile for uncompressed separately. More specifically, the
definition of the framework does not modify or update the definition
of the framework specified by RFC 3095.
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................4
2.1. Acronyms ...................................................4
2.2. ROHC Terminology ...........................................4
3. Background (Informative) ........................................7
3.1. Header Compression Fundamentals ............................7
3.2. A Short History of Header Compression ......................7
4. Overview of Robust Header Compression (ROHC) (Informative) ......8
4.1. General Principles .........................................8
4.2. Compression Efficiency, Robustness, and Transparency ......10
4.3. Developing the ROHC Protocol ..............................10
Jonsson, et al. Standards Track [Page 1]
RFC 4995 The ROHC Framework July 2007
4.4. Operational Characteristics of the ROHC Channel ...........11
4.5. Compression and Master Sequence Number (MSN) ..............13
4.6. Static and Dynamic Parts of a Context .....................13
5. The ROHC Framework (Normative) .................................14
5.1. The ROHC Channel ..........................................14
5.1.1. Contexts and Context Identifiers ...................14
5.1.2. Per-Channel Parameters .............................15
5.1.3. Persistence of Decompressor Contexts ...............16
5.2. ROHC Packets and Packet Types .............................16
5.2.1. General Format of ROHC Packets .....................17
5.2.1.1. Format of the Padding Octet ...............17
5.2.1.2. Format of the Add-CID Octet ...............18
5.2.1.3. General Format of Header ..................18
5.2.2. Initialization and Refresh (IR) Packet Types .......19
5.2.2.1. ROHC IR Packet Type .......................20
5.2.2.2. ROHC IR-DYN Packet Type ...................20
5.2.3. ROHC Initial Decompressor Processing ...............21
5.2.4. ROHC Feedback ......................................22
5.2.4.1. ROHC Feedback Format ......................23
5.2.5. ROHC Segmentation ..................................25
5.2.5.1. Segmentation Usage Considerations .........25
5.2.5.2. Segmentation Protocol .....................26
5.3. General Encoding Methods ..................................27
5.3.1. Header Compression CRCs, Coverage and Polynomials ..27
5.3.1.1. 8-bit CRCs in IR and IR-DYN Headers .......27
5.3.1.2. 3-bit CRC in Compressed Headers ...........27
5.3.1.3. 7-bit CRC in Compressed Headers ...........28
5.3.1.4. 32-bit Segmentation CRC ...................28
5.3.2. Self-Describing Variable-Length Values .............29
5.4. ROHC UNCOMPRESSED -- No Compression (Profile 0x0000) .....29
5.4.1. IR Packet ..........................................30
5.4.2. Normal Packet ......................................31
5.4.3. Decompressor Operation .............................31
5.4.4. Feedback ...........................................32
6. Overview of a ROHC Profile (Informative) .......................32
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