Subject: [Sip] Unsolicited NOTIFY needs format acceptance

From: "Vikram Chhibber" <[email-masked]>
Date: Tue, 20 May 2008 11:57:23 +0530

Hi All,

I would like to emphasize the need for adapting unsolicited NOTIFY as
a standard. We all are aware of so many commercial applications using
this mechanism. Also, for typical features of presence and
call-processing, user-agents make subscriptions for sip-profile, reg
event, presence/RLS, watcher-info, message waiting indication,
xcap-diff events etc.

There are overheads on both the network and UA for maintaining the
dialog states for all these subscriptions, excessive SIP messaging and
not to mention the high-availability complexities where a network node
has to mirror the dialog information on its peer.

There are many optimizations like multi dialog usage (RFC 5057) etc
but these lead to inter-operation issues as their implementation
varies vendor to vendor.

I would like to ask whether there is an effort to address these issues.

~Vikram
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From: "Vikram Chhibber" <[email-masked]>
Date: Tue, 20 May 2008 12:03:09 +0530

Definitely, unsolicited NOTIFY can not be substituted for presence
event where it would make watcher info. subscription to presence event
useless but it makes sense of using it for reg, sip-profile or message
waiting.

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From: "Sanjay Sinha (sanjsinh)" <[email-masked]>
Date: Tue, 20 May 2008 07:23:33 -0400

You can use INFO event package to negotiate events in context of a
dialog and use INFO for exchanging the events. For presence related
features related to configuration, I think it's better to use Publish
than unsolicited Notify.

Sanjay

>-----Original Message-----
>From: [email-masked] [mailto:[email-masked]] On 
>Behalf Of Vikram Chhibber
>Sent: Tuesday, May 20, 2008 2:33 AM
>To: [email-masked]
>Subject: Re: [Sip] Unsolicited NOTIFY needs format acceptance
>
>Definitely, unsolicited NOTIFY can not be substituted for 
>presence event where it would make watcher info. subscription 
>to presence event useless but it makes sense of using it for 
>reg, sip-profile or message waiting.
>
>This list is for NEW development of the core SIP Protocol Use 
>[email-masked] for questions on current sip

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From: Dean Willis <[email-masked]>
Date: Tue, 20 May 2008 09:29:17 -0500

On May 20, 2008, at 1:27 AM, Vikram Chhibber wrote:

> ...

I believe that standardization of unsolicited NOTIFY for the use cases  
you seem to be considering would have to occur "over the dead bodies"   
of a large proportion of this working group. They seem to feel very  
strongly about it. The one case where we used NOTIFY without SUBSCRIBE  
was REFER, and we ended up having to go back and work around that  
(norefersub).

There have been suggestions to develop a "compound subscription" that  
might allow a UA to solicit multiple sets of events using a single  
SUBSCRIBE. I believe this has some potential. The specification  
process would probably not be straightforward, however, due to the  
syntax involved.

It might also be possible to get the side effect of REGISTER from a  
SUBSCRIBE, thereby allowing a single compound SUBSCRIBE transaction to  
replace a REGISTER transaction and multiple SUBSCRIBE transactions.  
This would also be a non-trivial standardization effort, as it would  
require absorbing all of the functionality of draft-ietf-sip-outbound  
into the SUBSCRIBE transaction.

--
Dean

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From: [email-masked]
Date: Tue, 20 May 2008 16:11:14 -0400

From: "Vikram Chhibber" <[email-masked]>

   a standard.

There is a rather strong consensus that unsolicited NOTIFYs are a bad
idea.  If you would like to make the case that unsolicited NOTIFY
should be used as a technique, please do so.  But I doubt that the
working group will address issues regarding unsolicited NOTIFY as long
as it considers them to be intrinsically harmful.

Dale