Subject: [Sip] non-SUBSCRIBE mechanism in RFC3265

From: Tonny Kung <[email-masked]>
Date: Wed, 12 Mar 2008 23:12:05 +0800 (CST)

Hi all,

I have some questions regarding the non-SUBSCRIBE mechanism that's
 allowed in RFC3265 to create a subscription. I hope someone could clarify
 what is correct/allowed by the RFC.

1) Considering it is allowed to create an implicit subscription with
 REFER, then I assume an Event package can define any method to create a
 subscription?

2) Regarding the duration of the subscription. Is it ok to tie the
 duration to other application state of the dialog?
For example, if an implicit subscription is created with an INVITE
 dialog, is it allowed to terminate the subscription when the INVITE dialog
 is released? Or do we have to received NOTIFY with
 Subscription-State=terminated?

Thanks for your time.

Best regards,
Tonny
       
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From: Paul Kyzivat <[email-masked]>
Date: Wed, 12 Mar 2008 11:48:25 -0400

Tonny,

I believe the non-subscribe dialog wording in 3265 was included to
accommodate REFER. It also seems that in retrospect people wish that
exception had not been made. So planning to create a non-subscribe
subscription for some other purpose would most likely be a mistake.

A key requirement is that both parties need to agree that the
subscription is being created and how the dialog is established. (There
must be a dialog.)

IMO the expiration time for the implicit subscription is one of the
messy parts of the implicit subscription. I don't know of good solutions
for it.

	Paul

Tonny Kung wrote:
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---

From: [email-masked]
Date: Wed, 12 Mar 2008 13:10:35 -0500

From: Tonny Kung <[email-masked]>

It is clear that the notifier can terminate the subscription if the
resource in question ceases to exist.  But it seems that there should
always be a final NOTIFY to ensure the subscriber knows that the
subscription has been terminated.  In general, creating subscriptions
as the side-effect of other SIP activities is not generally a good
idea.

Dale