Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!linus!philabs!bywater!acheron!clarke
From: clarke@acheron.UUCP (Ed Clarke)
Newsgroups: comp.dcom.modems
Subject: Re: MNP make for a faster modem?
Message-ID: <505@acheron.UUCP>
Date: 30 Jan 88 17:25:33 GMT
References: <17586@topaz.rutgers.edu>
Organization: Ciliophora Associates
Lines: 32

in article <17586@topaz.rutgers.edu>, ron@topaz.rutgers.edu (Ron Natalie) says:
> 
> As someone already pointed out MNP only makes the data rate slower, it's
>

MNP Classes:

	1 - Block Mode, Half duplex, slowest ( nobody uses this one )
	2 - Stream Mode, Full duplex, 84% of non-MNP chars per second
	3 - Class 2 + synchronous transmission. 254 chars/sec @ 2400 baud
	    ( due to no start or stop bit overhead, 8 bits/char vs 10 )
	4 - Class 3 + bigger blocks + smaller header. 276 chars/sec @ 2400 baud
	5 - Class 4 + data compression. Throughput varies with data. May
	    be less efficient than class 4.

The above information is from the USR Courier HST modem instruction book and
the October, 1987 addendum to same.  Note that the initial MNP handshake may
prevent connection to a non-MNP modem.  Courier recommends that you disable
MNP if you know that the other modem does not support it.

The above data presumes no errors.  If you get errors, then throughput will
drop to much lower rates.  By the way, the compression description in the HST
manual sounds like a simple HASP compress, not LZ compression.  I could be
wrong though ( nothing like asking for flames! ).

ALSO!!! You have to be feeding the modem faster than 2400 baud (or 1200) to get
ANY improvement at all.  2400 in = 2400 out, and doesn't matter if you have a
T1 line in between.  The HST and others will accept 19200 in and out, with a
slower link in between (2400 for instance).  They handshake with CTS or by
XON/XOFF protocols.

Ed Clarke, Jr.