Subject: Re: your mail

From: "Slutsman, Lev A, ALSVC" <[email-masked]>
Date: Tue, 24 Aug 1999 15:46:16 -0400

To: "'mailto:[email-masked]'" <mailto:[email-masked]>,
        "[email-masked]'" <[email-masked]>
Subject: Bye message for PINT
Date: Tue, 24 Aug 1999 15:44:06 -0400
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   Bernie,
Good questions. As SUBSCRIBE/NOTIFY are not in the SIP/CORE, below is just
my point of view.
 In general, SIP servers perform request association based on a
Call-Leg=n(Call-ID, To,From). Therefore, to distinguish between BYE towards
INVITE from BYE towards SUBSCRIBE, we need two different Call-ID's.
The SIP client may link INVITE Call-ID with a Subscribe one for call
association.
Regards, 
Lev.

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From: Scott Petrack <[email-masked]>
Date: Thu, 26 Aug 1999 18:48:17 -0400 (EDT)

Although in the generic case one can use a new Call-ID for a subscribe,
by far the simplest thing to do is just to SUBSCRIBE with the old 
Call-ID. In this case there is no need to parse any SDP to find out
what you are subscribing to. This is certainly simpler.

And if you do this, an "unsubscribe" would be performed
just by using an Expires: header of 0.

Scott

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