Re: X.25 collisions

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Article #1059

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#1059

From: Jon lnes
Date: Mon, 28 Jan 1991 09:27

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According to my interpretation of X.25 you are right, and the state
tables are wrong. Examining the ISO sources for X.25 DTE operation
(ISO8208) I found the same error: E.g. receiving a CLEAR INDICATION
after sending a CLEAR REQUEST leads to a transition to the CLEAR
INDICATION state according to the tables, while according to the
text, the Clear procedure is completed, and the state transition
should be to state READY.
Note that for RESTART packets one condition exists where a RESTART
collision requires a repeated RESTART procedure: If communication
is from one DTE to another woth no intervening DCE (e.g. when using
X.25 in a LAN), and the Reference Number Facility is not used for
channel number allocation. In this case one DTE is required to act
as a DCE for channel number allocation - which one is determined
from the RESTART procedure. The DTE sending the RESTART will continue
to act as a DTE, while a DTE receiving a RESTART (from another DTE)
will act as a DCE for channel number allocation.
This situation is not resolved if a RESTART collision occurs.
Apart from this rather exotic case, a RESTART/CLEAR/RESET collision
completes the procedure - presumably both ends detected the same
error.

Jon Oelnes, Norwegian Computing Center, Oslo
E-mail: Jon.Olnes@nr.no   or    jon@ifi.uio.no

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From: jon@ifi.uio.no (Jon lnes)
Newsgroups: comp.protocols.iso
Subject: Re: X.25 collisions
Message-ID: <CMM.0.88.665054845.jon@gode.ifi.uio.no>
Date: 28 Jan 91 09:27:25 GMT
References: <WS.91Jan25190808@karl.tools.uucp>
Sender: jon@ifi.uio.no (Jon \lnes)
Organization: Dept. of Informatics, University of Oslo, Norway
Lines: 23
Nntp-Posting-Host: gode.ifi.uio.no
In-Reply-To: ws@tools.uucp (Wolfgang Solfrank)'s message of 25 Jan 91
        18:08:08 GMT
To: ws@tools.uucp (Wolfgang Solfrank)
Originator: jon@gode.ifi.uio.no

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