NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/comp/dcom/modems/18028

Internet Message Format | 1992-12-12 | 1.7 KB

Path: sparky!uunet!uunet.ca!xenitec!zswamp!geoff
From: [e-mail] (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: Re: Can V.32bis or V.42bis be 'faked' by software?
Message-ID: <[e-mail]>
Date: Sat, 12 Dec 92 12:16:37 EST
References: <[e-mail]>
Organization: Izot's Swamp
Lines: 24

[e-mail] (Rick Miller) writes:

> Exactly what *are* V.32bis and V.42bis?  Can this 'behaviour' be mimicked
> in software so that a vanilla 2400bps or 9600bps modem would 'look' like
> a V.32bis or V.42bis modem?

   V.32 and V.32bis are standards for encoding the bits into signal patterns
that can be carried over the phone.  Emulating it with a 2400 bps modem is out
of the question: a bicycle and a Porsche can both use the same road and move
people between places, but you can't make a bicycle look like a contender for
the Indy championship.

   V.42bis is data compression, and it can be added to almost any kind of
modem.  Unfortunately, V.42bis usually implies V.42 error correction, and that
requires a modem capable of synchronous operation.  That's no problem with a
genuine Hayes Smartmodem (hence the ease of adding a V-Series Modem Enhancer),
but difficult with normal 2400 bps modems.  MNP, on the other hand, can be
faked easily... but only in asynchronous mode, which takes away its
performance boost unless you're sending compressible data... in which case
you'd be better off to compress it before you send it anyway.

  Geoffrey Welsh, 7 Strath Humber Court, Islington, Ontario, M9A 4C8 Canada
[e-mail], [xenitec.on.ca|m2xenix.psg.com]!zswamp!geoff [phone]
       You're still young if your wallet is exhausted before you are.