Network Working Group C. Bormann, Editor, TZI/Uni Bremen
Request for Comments: 3095 C. Burmeister, Matsushita
Category: Standards Track M. Degermark, Univ. of Arizona
H. Fukushima, Matsushita
H. Hannu, Ericsson
L-E. Jonsson, Ericsson
R. Hakenberg, Matsushita
T. Koren, Cisco
K. Le, Nokia
Z. Liu, Nokia
A. Martensson, Ericsson
A. Miyazaki, Matsushita
K. Svanbro, Ericsson
T. Wiebke, Matsushita
T. Yoshimura, NTT DoCoMo
H. Zheng, Nokia
July 2001
RObust Header Compression (ROHC):
Framework and four profiles: RTP, UDP, ESP, and uncompressed
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 (2001). All Rights Reserved.
Abstract
This document specifies a highly robust and efficient header
compression scheme for RTP/UDP/IP (Real-Time Transport Protocol, User
Datagram Protocol, Internet Protocol), UDP/IP, and ESP/IP
(Encapsulating Security Payload) headers.
Existing header compression schemes do not work well when used over
links with significant error rates and long round-trip times. For
many bandwidth limited links where header compression is essential,
such characteristics are common.
Bormann, et al. Standards Track [Page 1]RFC 3095 Robust Header Compression July 2001
This is done in a framework designed to be extensible. For example,
a scheme for compressing TCP/IP headers will be simple to add, and is
in development. Headers specific to Mobile IPv4 are not subject to
special treatment, but are expected to be compressed sufficiently
well by the provided methods for compression of sequences of
extension headers and tunneling headers. For the most part, the same
will apply to work in progress on Mobile IPv6, but future work might
be required to handle some extension headers, when a standards track
Mobile IPv6 has been completed.
Table of Contents
1. Introduction....................................................6
2. Terminology.....................................................8
2.1. Acronyms.....................................................13
3. Background.....................................................14
3.1. Header compression fundamentals..............................14
3.2. Existing header compression schemes..........................14
3.3. Requirements on a new header compression scheme..............16
3.4. Classification of header fields..............................17
4. Header compression framework...................................18
4.1. Operating assumptions........................................18
4.2. Dynamicity...................................................19
4.3. Compression and decompression states.........................21
4.3.1. Compressor states..........................................21
4.3.1.1. Initialization and Refresh (IR) State....................22
4.3.1.2. First Order (FO) State...................................22
4.3.1.3. Second Order (SO) State..................................22
4.3.2. Decompressor states........................................23
4.4. Modes of operation...........................................23
4.4.1. Unidirectional mode -- U-mode..............................24
4.4.2. Bidirectional Optimistic mode -- O-mode....................25
4.4.3. Bidirectional Reliable mode -- R-mode......................25
4.5. Encoding methods.............................................25
4.5.1. Least Significant Bits (LSB) encoding .....................25
4.5.2. Window-based LSB encoding (W-LSB encoding).................28
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