IP Payload Compression Using ITU-T V.44 Packet Method
RFC 3051

Document Type RFC - Informational (January 2001; No errata)
Was draft-heath-ipcomp-v44 (individual)
Last updated 2013-03-02
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Network Working Group                                           J. Heath
Request for Comments: 3051                                     J. Border
Category: Informational                           Hughes Network Systems
                                                            January 2001

         IP Payload Compression Using ITU-T V.44 Packet Method

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document describes a compression method based on the data
   compression algorithm described in International Telecommunication
   Union (ITU-T) Recommendation V.44.  Recommendation V.44 is a modem
   standard but Annex B, Clause B.1, of the recommendation describes the
   implementation of V.44 in packet networks (e.g., V.44 Packet Method).
   This document defines the application of V.44 Packet Method to the
   Internet Protocol (IP) Payload Compression Protocol (RFC 2393).  RFC
   2393 defines a method for applying lossless compression to the
   payload portion of IP datagrams.

   V.44 Packet Method is based upon the LZJH data compression algorithm.
   Throughout the remainder of this document the terms V.44 Packet
   Method and LZJH are synonymous.

Heath & Border               Informational                      [Page 1]
RFC 3051        IP Payload Compression Using ITU-T V.44     January 2001

Table of Contents

    1. Introduction...................................................2
       1.1 General....................................................2
       1.2 Background of LZJH Data Compression........................2
       1.3 Intellectual Property Rights...............................3
       1.4 Specification of Requirements..............................4
    2. Compression Process............................................4
       2.1 Encoder Dictionary.........................................4
       2.2 Encoder Output.............................................4
       2.3 Padding....................................................4
    3. Decompression Process..........................................5
       3.1 Compressed Datagram........................................5
       3.2 Original Uncompressed Datagram.............................5
    4. IPComp Association (IPCA) Parameters...........................5
       4.1 Transform ID...............................................5
       4.2 Security Association Attributes............................5
       4.3 Manual configuration.......................................5
       4.4 Minimum packet size threshold..............................6
       4.5 Compressibility test.......................................6
    5. Security Considerations........................................6
    6. IANA Considerations............................................6
    7. Acknowledgements...............................................6
    8. References.....................................................6
    9. Authors' Addresses.............................................7
   10. Full Copyright Statement.......................................8

1. Introduction

1.1 General

   This document specifies the application of LZJH data compression, a
   lossless data compression algorithm, to IP datagram payloads.  LZJH
   data compression is to be used in conjunction with the IP Payload
   Compression Protocol (IPComp) [RFC2393].  This document is written
   with the assumption that the reader has an understanding of the
   IPComp protocol.

1.2 Background of LZJH Data Compression

   LZJH is similar to the algorithm described in [LZ78] although it also
   has aspects which are similar to the algorithm described in [LZ77].
   As such, it provides the execution speed and low memory requirements
   of [LZ78] with compression ratios that are better than [LZ77].
   Originally developed for the satellite industry to compress IP
   datagrams independently, it is ideal for the IPComp application.  The
   LZJH algorithm was modified to compress a continuous stream of data
   for a modem environment and this modified version is the basis for

Heath & Border               Informational                      [Page 2]
RFC 3051        IP Payload Compression Using ITU-T V.44     January 2001

   Recommendation V.44.  LZJH is an adaptive, general purpose, lossless
   data compression algorithm.  It was selected by the ITU-T as the
   basis for Recommendation V.44 based on its performance across a wide
   variety of data types, particularly web HTML's, and based on its
   compression ratio characteristics, per MIP and memory utilized (as
   compared to other candidate algorithms).  Its encoder is extremely
   efficient and can encode a two character string with 3 bits the
   second time that string is encountered in the data.
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