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From: karn@ka9q.bellcore.com (Phil Karn)
Newsgroups: comp.dcom.lans
Subject: Re: What services does X.25 provide?
Keywords: x.25, services, login, e-mail, file transfer, IPC
Message-ID: <17899@bellcore.bellcore.com>
Date: 16 Oct 89 15:55:17 GMT
References: <796@maxim.erbe.se> <3279@wasatch.utah.edu> <522@wet.UUCP> <6624@pdn.paradyne.com> <23189@cos.com> <1989Oct10.210812.13144@agate.berkeley.edu>
Sender: news@bellcore.bellcore.com
Reply-To: karn@ka9q.bellcore.com (Phil Karn)
Organization: Secular Humanists for No-Code
Lines: 33

>Why not just run TP4 everywhere?  It could run over X.25 just as well
>as over connectionless, couldn't it?  That would at least reduce the
>number of complexities in OSI by a large amount.  What do TP0-TP3
>give you that TP4 doesn't?  (This question was raised by someone at
>InterOp and no one even tried to answer it--does this mean it was
>an extremely stupid question or an extremely good one?)

That's actually an extremely good question. The answer has to do with
the *real* motivation behind OSI -- namely, the *thwarting* of true,
interoperable internetworking by the European PTTs in order to protect
their X.25 network monopolies. There can be no other explanation for the
existence of five separate and incompatible "transport classes" in OSI,
all providing the same connection-oriented service to the next higher
layer. It is often said that the US must "migrate" to OSI "so we can
talk to the Europeans." But the sad truth is that the Europeans will use
TP0 above X.25 while the US will use TP4 above CLNS. The result will be
two (or more) incompatible islands, even though both will be nominally
"OSI compliant".

OSI is the biggest bill of goods that has ever been sold to the US
government (with the possible exception of SDI). Anyone in Europe (or
elsewhere) who is seriously interested in true multivendor
internetworking is already running TCP/IP, and its use in Europe is
growing rapidly despite the best efforts of the local governments to
stamp it out.

It would have been far better had the TP-4 and CLNS protocols never been
added to OSI; then those interested in serious internetworking would
never have been fooled by the OSI siren song into the upcoming Chinese
Fire Drill that will be the TCP-to-OSI "migration".  The European PTTs
must be laughing their heads off about now.

Phil