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From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.dcom.lans,comp.protocols.misc,comp.sources.wanted
Subject: Re: OSI-model software
Message-ID: <1204@botter.cs.vu.nl>
Date: Tue, 9-Jun-87 06:46:49 EDT
Article-I.D.: botter.1204
Posted: Tue Jun  9 06:46:49 1987
Date-Received: Fri, 12-Jun-87 01:44:44 EDT
References: <223@diab.UUCP> <233@idacrd.UUCP> <526@alliant.UUCP> <19265@ucbvax.BERKELEY.EDU> <492@houxa.UUCP>
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
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Organization: VU Informatica, Amsterdam
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In article <492@houxa.UUCP> mel1@houxa.UUCP (M.HAAS) writes:
>What does ISO offer that TCP/IP doesn't?  Is it significantly faster?
>I can't think of any other measure that needs improving.
>
>Is there a war going on?  TCP/IP vs ISO?  Who is on which side?  Why?

The ISO OSI model is an attempt to provide a framework for networking from
the physical bit transport to the applications.  The model itself does not
contain protocols at all, although ISO has standardized some protocols and
services for the various layers.

TCP and IP are two specific protocols for layers 4 and 3, respectively, and
as such can be used to fill two of the slots in the OSI reference model.
Other protocols are needed for the other layers.

Virtually everyone now agrees that the OSI model is a good way to look at
networking.  The war is about which protocols which be used in which layer.
TCP is clearly one candidate for the transport protocol, but most
companies in the U.S., and virtually all companies outside the U.S. are
committed to supporting the ISO OSI transport protocol and the ISO protocols
in layers 5 through 7 too.  (1-3 are much fuzzier, what with IEEE 802 etc.)

There has been a lot of generalized disgust with OSI expressed here and
elsewhere.  I would be very interested in hearing specific comments about
  1. What is wrong with the OSI model itself.
  2. What is wrong with the specific protocols ISO has adopted.

Comments like: you can't go out and buy it off the shelf right now don't
count.  If the standards people waited until every company had already
had a running network product, they would all be different and there would
be no standard at all.  The only way to achieve standardization in this area
is to agree on the standards before every company invests a lot of money
doing it some nonstandard way.  Thus it is not surprising that the standards
are here before all the implementations.

Nevertheless, there are certainly plenty of valid criticisms of the model and
the protocols (e.g., the session layer is pointless, the presentation layer
is practically empty, they forgot about encryption altogether etc.).  I would
like to see a discussion of this subject, preferably by people who know what
they are talking about.

Andy Tanenbaum (ast@cs.vu.nl)