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
datatracker.ietf.org