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From: dan@haddock.UUCP
Newsgroups: net.lan
Subject: Re: ISO Class 4 - what is it?
Message-ID: <19000003@haddock.UUCP>
Date: Sun, 26-May-85 22:25:00 EDT
Article-I.D.: haddock.19000003
Posted: Sun May 26 22:25:00 1985
Date-Received: Thu, 30-May-85 03:43:47 EDT
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Nf-From: haddock!dan    May 26 22:25:00 1985


I attended a lecture on this subject a while back.  As I recall,
the term "ISO Transport Class 4 protocol" does refer to a TCP-like protocol.
The different classes of transport layer make different assumptions about
the reliability, etc. of the lower layer, and may also provide slightly
different services to the next layer up.

The American member(s) of ISO pushed for a TCP-like transport layer, with
much resistance from the rest of ISO, and the different classes of transport
layer were the result.  Class 0 is a null layer; it assumes that the layer
underneath Transport provides reliable, error-free transmission.  The other
classes assume different kinds of potential failure of the lower layer.

	Dan Franklin