Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!uunet!hayes!tnixon
From: tnixon@hayes.uucp
Newsgroups: comp.dcom.modems
Subject: Re: V.32bis vs V.32
Message-ID: <3835.27d649d6@hayes.uucp>
Date: 7 Mar 91 14:10:30 GMT
References: <1991Mar6.165542.10140@cs.mcgill.ca>
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 35

In article <1991Mar6.165542.10140@cs.mcgill.ca>, storm@cs.mcgill.ca
(Marc WANDSCHNEIDER) writes: 

>     What is the difference between V.32 and V.32bis...?  Is V.32bis a 
> transfer protocol as is V.32, or is it something else...?

V.32 provides full-duplex, async or sync transmission at 4800 and 
9600bps on two-wire dial-up or leased lines.  To change speeds, you 
must retrain the modems, which takes five to ten seconds.

V.32bis provides full-duplex, async or sync transmission at 4800, 
7200, 9600, 12000, and 14400bps on two-wire dial-up or leased lines. 
It is backward-compatible with V.32.  In addition to the retrain 
mechanism for speed changes, V.32bis also provides a "rapid rate 
renegotiation" capability, which allows the modems (if mutually 
agreeable) to change rates up or down in about 1/10th of a second.

>     What sort of throughput can one expect (theoretically I suppse) using a 
> V.32bis modem with V.42bis compression...?

If you accept that V.42bis achieves up to 4-to-1 compression on text 
data, you could expect to see up to 57,600bps throughput with 
V.42bis over V.32bis.  This is quite dependent on the modem 
implementation.  Many vendors are sticking with a maximum 38,400bps 
interface rate, and using the increased modulation speed of V.32bis 
to increase the types of data that actually acheive 38,400bps 
throughput, rather than trying to push for more.  V.32bis also 
increases the throughput of uncompressible data and of synchronous 
transmissions.

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-840-9200  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
P.O. Box 105203                   | UUCP uunet!hayes!tnixon  AT&T    !tnixon
Atlanta, Georgia  30348  USA      | Internet       hayes!tnixon@uunet.uu.net