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From: hlh@awsum.UUCP (Henry L. Hall)
Newsgroups: net.unix-wizards
Subject: Re: Unix and Telebit modems
Message-ID: <218@awsum.UUCP>
Date: Fri, 9-May-86 19:25:12 EDT
Article-I.D.: awsum.218
Posted: Fri May  9 19:25:12 1986
Date-Received: Mon, 12-May-86 00:21:07 EDT
References: <510@brl-smoke.ARPA>
Organization: Communication Machinery Corp.  Framingham, MA
Lines: 28
Summary: A comment

In article <510@brl-smoke.ARPA>, lauren@rand-unix.arpa writes:
> .....  Protocols (like for running above real X.25/TCP links) designed 
> to run on top of "conventional" error-free links generally perform badly 
> in these sorts of situations, both due to modem characteristics and flow
> control problems.  That is, when the underlying communications path
> isn't already totally error-corrected and flow-controlled from computer
> to computer, not just from modem to modem, there's trouble with those
> sorts of protocols.  In other words, protocols designed to run over 
> X.25 or TCP links will not perform well when they're not actually being
> run over X.25/TCP-type computer to computer error corrected and
> flow-controlled links.  Factors such as system loading, type of
> serial port hardware, and a variety of other issues all enter the picture.

A comment I'd like to make would be, why not use an intelligent controller
which can ease the load on a computer by quite a considerable amount.  There
are several intelligent controller manufacturers which do have a TCP / X.25
interface which can handle a high speed RS-232 interface on the modem side,
and which interface directly to a computer system's bus.  System loading
and system bus loading can possibly be a factor (a system can't get the data
off the card quickly enough) but might be solved by having a large enough
packet buffer memory.

Helpful commentary welcomed.  Thanks.

-- 
Henry L. Hall
Communication Machinery Corp., East Coast
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