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From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.dcom.modems
Subject: MNP3 on a BELL 103J modems (was Re: Summary of 9600 V.32 bis info)
Summary: Can't do it.
Message-ID: <1991Jun3.013635.14493@netcom.COM>
Date: 3 Jun 91 01:36:35 GMT
References: <147.28486D85@zswamp.uucp>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 27

In article <147.28486D85@zswamp.uucp> root@zswamp.uucp (Geoffrey Welsh) writes:
>
>   If someone could be bothered to impliment MNP3 and 4 on a Bell 103J modem, 
>I'm sure that you could get the same relative speed boost at 300 bps.
>

It's not so much as bothering to do it (after all, the modem designers
already did  it for the faster modulations, right?), as it is impossible
to implement MNP3 or V.42 over a Bell 103J modulation (or V.21).

MNP3 and V.42 rely on the modems having a synchronous link through the phone
line (otherwise you can't use the HDLC-like framing which allows the stripping
of start and stop bits).  Bell 103J and V.21 are not synchronous modulations.

That wouldn't stop anyone from implementing MNP2 as the base protocol and
adding MNP4 header reduction and MNP5 data compression.  I believe that's
exactly what the software MNP implementations do.
 

>Geoffrey Welsh - Operator, Izot's Swamp BBS (FidoNet 1:221/171)
>root@zswamp.uucp or ..uunet!watmath!xenitec!zswamp!root

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 |  Greg Andrews   |       UUCP: {apple,amdahl,claris}!netcom!gandrews    |
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