Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!hayes!tnixon
From: tnixon@hayes.uucp
Newsgroups: comp.dcom.modems
Subject: Re: HST/V.32bis Performance
Message-ID: <3844.27da8d2c@hayes.uucp>
Date: 10 Mar 91 19:46:52 GMT
References: <139@ns.UUCP> <3811.27ca371e@hayes.uucp> <141@ns.UUCP>
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 26

In article <141@ns.UUCP>, bob@ns.UUCP (Bob Mathias) writes:

> Since I'm seeing such a difference, is there any why I shouldn't
> disable LAPM and use MNP4.  What are the benefits of LAPM over MNP4?

LAPM has superior error detection and recovery mechanisms, including 
(optional) 32-bit FCS and Selective Reject, separate REJ, RR, and 
RNR frames to avoid protocol confusion, etc.  The smaller default 
frame size also allows you to recover from errors faster, at the 
expense of a couple of percent throughput on clean lines.  
Admittedly, these benefits are ALL meaningless if you have a 
perfectly clean line, but if we all had perfect lines we wouldn't 
need error control at all (except for the fact that we can improve 
throughput by stripping start and stop bits and implementing data 
compression).

I'm quite certain that the differences you're seeing in the HST are 
directly related to their implementation, and are not inherent in 
the protocol itself.  But if that's what you're seeing, you might as 
well go with what works best.

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-840-9200  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
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