Binkp optional protocol extension Dataframe Compression

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FTSC                             FIDONET TECHNICAL STANDARDS COMMITTEE
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Publication:    FTS-1029
Revision:       1
Title:          Binkp optional protocol extension Dataframe
                Compression
Authors:        Alex Shakhaylo
Issue Date:     1 December 2005
Review Date:    1 December 2007
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Contents:
                1. Binkp Dataframe Compression
                A. References
                B. History
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Status of this document
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   This document is a Fidonet Technical Standard (FTS).

   This document specifies an optional Fidonet standard protocol for
   the Fidonet community.

   This document is released to the public domain, and may be used,
   copied or modified for any purpose whatever.


1. Binkp Dataframe Compression
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   A session is in PLZ mode in case the both sides set "PLZ" flag in
   any of M_NUL "OPT" packets. This extension may be used in both
   binkp/1.0 and binkp/1.1 protocol versions.

   To compress dataframes in PLZ mode ZLib library (by Jean-loup
   Gailly and Mark Adler) is used.

   It is assumed that in PLZ mode any dataframe withing the regular
   data exchange may be compressed with 'compress' or 'compress2'
   methods of ZLib library. Compressed dataframes are indicated by
   setting the second high bit of the high byte of the frame header.
   Thus the biggest dataframe in PLZ mode cannot exceed
   00111111 11111111 = 0x3FFF = 16383 bytes.

   At any moment during a session any side may swith off PLZ mode by
   sending M_GET command with additional parameter 'NZ' (for example:
   M_GET "config.sys 125 2476327846 100 NZ", this command requests to
   switch off PLZ mode and to resend "config.sys" file from offset
   100). A position of 'NZ' additional parameter in M_GET command is
   not fixed, because of other optional extensions which can also use
   additional parameters.

A. References
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   [FSP-1018]
           Binkp 1.0 Protocol specification.


B. History
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   Rev.1, 20051201: Initial Release.