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PPP Deflate Protocol
RFC 1979

Document type: RFC - Informational (August 1996; Errata)
Document stream: IETF
Last updated: 2013-03-02
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IESG State: RFC 1979 (Informational)
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Network Working Group                                           J. Woods
Request for Comments: 1979                                 Proteon, Inc.
Category: Informational                                      August 1996

                          PPP Deflate Protocol

Status of This Memo

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

Abstract

   The Point-to-Point Protocol (PPP) [1] provides a standard method for
   transporting multi-protocol datagrams over point-to-point links.

   The PPP Compression Control Protocol [2] provides a method to
   negotiate and utilize compression protocols over PPP encapsulated
   links.

   This document describes the use of the PPP Deflate compression
   protocol for compressing PPP encapsulated packets.

Table of Contents

     1.     Introduction ......................................    2
        1.1       Licensing ...................................    2
     2.     PPP Deflate Packets ...............................    3
        2.1       Packet Format ...............................    6
     3.     Configuration Option Format .......................    8
     SECURITY CONSIDERATIONS ..................................    9
     REFERENCES ...............................................    9
     ACKNOWLEDGEMENTS .........................................    9
     CHAIR'S ADDRESS ..........................................   10
     AUTHOR'S ADDRESS .........................................   10

Woods                        Informational                      [Page 1]
RFC 1979                      PPP Deflate                    August 1996

1.  Introduction

The 'deflate' compression format[3], as used by the PKZIP and gzip
compressors and as embodied in the freely and widely distributed
zlib[4] library source code, has the following features:

       - an apparently unencumbered encoding and compression
         algorithm, with an open and publically-available
         specification.

       - low-overhead escape mechanism for incompressible data.  The
         PPP Deflate specification offers options to reduce that
         overhead further.

       - heavily used for many years in networks, on modem and other
         point-to-point links to transfer files for personal computers
         and workstations.

       - easily achieves 2:1 compression on the Calgary corpus[5]
         using less than 64KBytes of memory on both sender and
         receive.

1.1.  Licensing

   The zlib source is widely and freely available, subject to the
   following copyright:

      (C) 1995 Jean-Loup Gailly and Mark Adler

       This software is provided 'as-is', without any express or implied
       warranty.  In no event will the authors be held liable for any
       damages arising from the use of this software.

       Permission is granted to anyone to use this software for any
       purpose, including commercial applications, and to alter it and
       redistribute it freely, subject to the following restrictions:

       1. The origin of this software must not be misrepresented; you
          must not claim that you wrote the original software. If you
          use this software in a product, an acknowledgment in the
          product documentation would be appreciated but is not
          required.

       2. Altered source versions must be plainly marked as such, and
          must not be misrepresented as being the original software.

Woods                        Informational                      [Page 2]
RFC 1979                      PPP Deflate                    August 1996

       3. This notice may not be removed or altered from any source
          distribution.

       Jean-Loup Gailly        Mark Adler
       gzip@prep.ai.mit.edu    madler@alumni.caltech.edu

      If you use the zlib library in a product, we would appreciate
      *not* receiving lengthy legal documents to sign. The sources are
      provided for free but without warranty of any kind.  The library
      has been entirely written by Jean-Loup Gailly and Mark Adler; it
      does not include third-party code.

   The deflate format and compression algorithm are based on Lempel-Ziv
   LZ77 compression; extensive research has been done by the GNU Project
   and the Portable Network Graphics working group supporting its patent
   free status.

2.  PPP Deflate Packets

   Before any PPP Deflate packets may be communicated, PPP must reach
   the Network-Layer Protocol phase, and the CCP Control Protocol must
   reach the Opened state.

   Exactly one PPP Deflate datagram is encapsulated in the PPP
   Information field, where the PPP Protocol field contains 0xFD or

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