Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!MIRSA.INRIA.FR!Christian.Huitema
From: Christian.Huitema@MIRSA.INRIA.FR (Christian Huitema)
Newsgroups: comp.protocols.iso
Subject: Re: X-WINDOWS & OSI
Message-ID: <8906290745.AA04584@jerry.inria.fr>
Date: 29 Jun 89 07:45:35 GMT
References: <228@crltrx.crl.dec.com>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 25

I really dont understand why ACSE should cost 2 or 3 seconds. Opening
the session + the association is done with a single message exchange,
after transport set up. There is no reason that a transport set up
would cost much more than a TCP set up, and there is no fundamental
reason, apart from poor software enginnering, that a single message
exchange should cost more over transport than it costs over TCP.

Given that the current proposal proposes to *use* this single exchange
for an useful purpose -- opening a window -- I dont think that the
delay will much more important than that of running over TCP-IP. One
can estimate the overhead by deriving it from the current size of the
connection message using S+P+ACSE, approx 250 bytes; I dont see how
processing 250 bytes of data would cost ``2 to 3 seconds'' -- I would
rather expect milliseconds. Real delays derives from synchronisations,
i.e. sending messages and waiting for responses, and they are protocol
independant; the opening of a window will always introduce such a synchronisation.

I can find only two explanations for the alleged long delays. One would
be the responsive time from a name server embedded in the association
package, but then one should compare it to the response time of the
DNS. The other one would be the massive CPU overhead introduced by
security procedures, e.g. computing a 150 digits RSA signature; but
this is quite another game.

Christian Huitema