Path: utzoo!attcan!uunet!hayes!tnixon
From: tnixon@hayes.uucp (Toby Nixon)
Newsgroups: comp.dcom.modems
Subject: Re: USR 9600 baud dual standard - V.42bis throughput
Message-ID: <1857@hayes.uucp>
Date: 8 Oct 90 10:52:14 GMT
References: <1990Sep30.024433.28717@athena.mit.edu> <1990Sep30.171414.5132@nstar.uucp> <1990Oct1.175833.28288@athena.mit.edu> <1990Oct2.092 <1990Oct06.145608.15322@scuzzy.in-berlin.de>
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 25

In article <1990Oct06.145608.15322@scuzzy.in-berlin.de>,
src@scuzzy.in-berlin.de (Heiko Blume) writes: 

> just a fact: we now use HSTs with V.42bis for getting (precompressed) news,
> and have an average throughput of 1644 bps, thats 5.9MB per hour. we love it!
> 
> a question, while i'm at it: is V.42bis asymmetric like the HST protocol
> (with a slow backchannel) ?? theres nothing about it in the manual.

V.42bis is a DATA COMPRESSION SCHEME, not a modulation technique.  
It will work equally well in symmetric or asymmetric modulation 
applications.  It is currently standardized only for use on top of 
V.42 LAPM error control protocol, and V.42 LAPM is currently 
standardized only for use in SYMMETRICAL modems that use 
async-to-sync conversion.  It only takes very minor tweeks to LAPM 
to make it work in an asymmetrical or half-duplex environment, 
however (slight timer value changes).  

	-- Toby

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