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From: mgh@mtunh.UUCP (Marcus Hand)
Newsgroups: net.lan
Subject: Re: ISO Class 4 - what is it?
Message-ID: <451@mtunh.UUCP>
Date: Tue, 28-May-85 21:53:00 EDT
Article-I.D.: mtunh.451
Posted: Tue May 28 21:53:00 1985
Date-Received: Thu, 30-May-85 03:19:13 EDT
References: <1302@ecsvax.UUCP>
Organization: AT&T Information Systems Laboratories, Holmdel, NJ
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>Just what is meant by ... "ISO Transport Class 4 Protocol"

The classes refer to reliability of transport service provided by the
transport provider  which implements the transport layer. Gulp.

They range from class 1 which is "no error detection, no flow control"
to class 5 "flow control, error detection with error correction".
Class 2 is essentially what you would use for a datagram service,
while you would use 4 or 5 for virtual circuit service.

If you're really interested in the ISO OSI-RM you should check out 
one of the back issues of the IEEE magazine  --  one of them was a special
issue devoted to it.  (I think we are talking of the Transactions of IEEE)

Finally,  the calsses may be numbered 0-4 and not 1-5 (I forget).

-- 
			Marcus Hand	(mtunh!mgh)