Subject: Re: [Sipping] Reminder: WG item : dialog-usage

From: "Christer Holmberg" <[email-masked]>
Date: Tue, 7 Mar 2006 00:18:49 +0200

Hi Paul,

I agree there will be a default expiration time - I just think it would be good to mention it, in order to avoid hanging dialogs.

But, if it already is mentioned somewhere I appologize for having missed it.

Regards,

Christer

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From: Paul Kyzivat <[email-masked]>
Date: Mon, 06 Mar 2006 18:45:34 -0500

> But, if it already is mentioned somewhere I appologize for having missed it.

3515 mentions this, and says that the notifier chooses the duration and 
informs the watcher in the notify. This of course leaves a window, 
before the receipt of the first notify, when the watcher doesn't have an 
expiration time for the subscription. AFAIK there is no explanation of 
how to deal with this.

IMO the right thing to do here would be to initially set that expiration 
time to the interval within which the initial notify must be sent, 
accounting for some extra time for retransmissions, etc. Unfortunately, 
AFAIK there is nowhere a definition for the time interval after which 
the initial (immediate) NOTIFY of a subscription must be sent. IMO it 
would probably be ok to set this to one minute.

The initial value, at the UAC, of the subscription for a REFER, before 
the NOTIFY is received, ought to be specified somewhere. And the time 
before the initial notification of a subscription is overdue also ought 
to be specified somewhere. But this is probably not the draft in which 
to do those things. For this draft I think it is sufficient to specify 
that a subscription expiration time is an attribute of a subscribe 
dialog usage.

	Paul