Subject: RE: [Megaco] Race condition between Modify and Subtract

From: "Tom-PT Taylor" <[email-masked]>
Date: Mon, 19 Nov 2001 08:53:44 -0500

There are two possible error conditions here.  If neither condition applies,
the command must be processed without regard to any possible misordering,
because you have no choice -- the misordering is indetectible.

The two error conditions are:
 -- termination appears in the wrong context (typically it is in NULL, but
its previous context is specified)
 -- termination no longer exists (was an ephemeral)

-----Original Message-----
From: Raphael Tryster [mailto:[email-masked]]
Sent: Sunday, November 18, 2001 8:55 AM
To: [email-masked]
Subject: [Megaco] Race condition between Modify and Subtract

I have a question about RFC 3015 paragraph 9.1.2, which states that "...a
media gateway may sometimes receive a Modify command that applies to a
previously subtracted termination.  Such commands should be ignored, and an
error code should be returned".
Since it is permitted for Modify commands to operate on terminations that
are in the Null context, how does an MG distinguish between the following
cases?
Modify was sent before Subtract, but the commands were received in the wrong
order.  The MG should ignore the Modify. 
Subtract was sent (possibly long) before Modify, and received in the same
order.  The MG should process the Modify because this is the beginning of
setting up a new call. 

Could the context id of the Modify command be used to distinguish the cases?
Perhaps a Modify command that refers to the termination in the Null context
should be considered new and processed, while a Modify command that refers
to the termination in a non-Null context (while the MG considers the
termination to be in the Null context) should be considered obsolete and
ignored.  This solution looks less attractive when we consider that the
rules might be different if the command is Add or Move instead of Modify.
Any other ideas as to how to make this distinction? 
Raphael Tryster 

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From: "PSK Chakravarthi" <[email-masked]>
Date: Tue, 20 Nov 2001 09:22:26 +0530

List,

Can gateway send Service Change with method=RESTRT and termination Id= specific
termination ID without sending Service change with Forced/Garaceful for that
termination Id?  If so what should be the MGC action for such a service change?
or
Can gateway send a service change with method=Restart for a termination Id which
is invloved in a call?

Thanks
Chak

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From: "PSK Chakravarthi" <[email-masked]>
Date: Tue, 20 Nov 2001 09:22:26 +0530

List,

Thanks
Chak