Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!ulysses!andante!princeton!udel!rochester!ur-tut!sunybcs!bingvaxu!leah!uwmcsd1!lakesys!craig
From: craig@lakesys.UUCP
Newsgroups: comp.dcom.modems
Subject: Re: MNP - Level 1-7
Message-ID: <813@lakesys.UUCP>
Date: 12 Jul 88 22:30:33 GMT
References: <27800001@ntvax> <7419@elroy.Jpl.Nasa.Gov>
Reply-To: craig@lakesys.UUCP (Craig Stodolenak)
Organization: Lake Systems - Milwaukee, WI
Lines: 53

In article <7419@elroy.Jpl.Nasa.Gov> david@elroy.Jpl.Nasa.Gov (David Robinson) writes:
>
>I am new to the MNP world (read VERY new) so could someone
>send me a small 2-3 line summary of each level and how they
>differ from each other?
>

(the following is Copyright 1987, Multi-Tech Systems, Inc.)

The MNP protocol is divided into several levels, or "Classes".  The classes
you would encounter in 1200 and 2400 bps modems are CLasses 2 through 5.  When
modems equipped with MNP start communicating, they will negotiate operation to
the highest common MNP class between them and operate at that level.  In order
to alleviate some of the confusion regardig different MNP Classes, we will
summarize them here:

CLASS 2
        This is a character (Byte) oriented protocol, where complete
asynchonous characters are thransmitted along with the protocol overhead.
This results in a throughput of only about 84%, which for a 2400 bps modem
would yield a transmission rate of about 2000 bps.  Relatively few modems were
ever sold incoprorating hardware-based Class 2 MNP, although this class has
been used in software-based applications.

CLASS 3
        This is a bit-oriented protocol, where asynchronous characters are
converted to a synchronous data stream, as explained earier in this chapter.
The protocl effieincy is about 108%, which yields a throughput of up to 2600
bps for a 2400 bps modem.  Virtually all MNP modems sold today utilize Class
3.  Both Class 2 and Class 3 are now public dimain protocls, and Class 3 has
achieved "industry standard" status.

CLASS 4
        Class 4 is nearly identical to Class 3, except that it can yield a
slightly better throughput.  The Class 4 protocol is flexible in the size of
the blocks that are transmitted, and by monitoring the data transmission
quality, will permit larger blocks during times of lower error activity.
These larger block tranmissions can increase the protocol efficiency to about
120%, for a potential throughput of about 2900 bps for a 2400 bps modem.

CLASS 5
        Class 5 includes the features of Classes 3 and 4, and also uses data
compression techniques to increase throughput.  Depending upon the type of
data being transmitted, the throughput of a Class 5 MNP 2400 bos modem canbe
up to 4800 bps.

I have no information regarding Classes 6 or 7, sorry...

-- 
Craig L. Stodolenak   | {backbone,uunet}!marque!lakesys!craig
8307 W. Grantosa Dr.  | craig@lakesys.UUCP
Milwaukee, WI  53218  |-------------------------------------------------------
(414) 462-8973        | "It is a moral imperitive." - 'Real Genius'