Article View: comp.protocols.iso
Article #575Re: question about SPDU
From: Harald Tveit Alvestrand
Date: Fri, 08 Jun 1990 07:26
Date: Fri, 08 Jun 1990 07:26
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The Session layer is actually a collapse of two protocol layers of the Teletex(1976?) protocol. So, the GT and PT (Grant Token and Please Token) are used as "here comes a higher-level PDU" signals, carrying no real meaning. You actually have to read the specs carefully to detect this; they document it as if you are allowed to concatenate several SPDUs into one TSDU, and list a few "allowed concatenation sequences". It took me quite some time to find out that most PDUs that were in the "document layer" of Teletex were now in a class that could NOT be first in a concatenation series, but that GT and PT could be first, and carried no real meaning if they did not have any parameters (LI=0). So much for removing layers by cryptic documentation! Harald Tveit Alvestrand X.400 expert, UNINETT MHS manager
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!nuug!sigyn.idt.unit.no!lear!hta From: harald.alvestrand@elab-runit.sintef.no (Harald Tveit Alvestrand) Newsgroups: comp.protocols.iso Subject: Re: question about SPDU Message-ID: <1990Jun8.072624.5598@idt.unit.no> Date: 8 Jun 90 07:26:24 GMT References: <9006051437.AA12834@ucbvax.Berkeley.EDU> Sender: news@idt.unit.no (Usenet news admin) Reply-To: harald.alvestrand@elab-runit.sintef.no Organization: ELAB-RUNIT, SINTEF, Norway Lines: 16