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RObust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed
RFC 3095

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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