Subject: [Sip] FW: New Draft - Suppression of Refer Implicit Subscription

From: "Sriram Parameswar" <[email-masked]>
Date: Mon, 28 Oct 2002 03:00:12 -0600

Hi All,

I have submitted a draft (to SIPPING) that examines the requirements and one
_potential_ mechanism to suppress the implicit subscription created by the
REFER method.

Till it appears in the IETF site - please pick up a copy at the site below:

http://home.attbi.com/~sriramkp/draft-parameswar-sipping-norefersub-00.txt

<abstract>
   The recipient of the REFER method [1] creates an implicit
   subscription to the 'refer' event. This subscription causes the REFER
   recipient to send NOTIFY messages to the sender informing him of the
   progress of the REFER. This memo provides for the requirements and
   one potential mechanism to suppress the creation of this implicit
   subscription, via an option tag - 'norefersub'. This gives the agent
   sending the REFER control over the creation of the subscription,
   while being backwards compatible with [1].
</abstract>

Your comments are highly appreciated.

Regards,

Sriram Parameswar

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---

From: Rohan Mahy <[email-masked]>
Date: Mon, 28 Oct 2002 21:20:55 -0800

Hi,

So you are just trading a pair of messages (NOTIFY/481) for an option  
tag in the REFER?  It doesn't seem that compelling to me personally.   
It certainly doesn't follow the generality over efficiency argument.   
Can you elaborate a bit more on your motivations?  The transfer draft  
recommends waiting for NOTIFY for attended transfer for robustness, so  
I'm not convinced there.  As for the "push content" model, I envisioned  
an immediate fetch, with a NOTIFY to deliver the status of that fetch.

thanks,
-rohan

---

From: "Sriram Parameswar" <[email-masked]>
Date: Tue, 29 Oct 2002 10:07:18 -0600

Rohan,

Thank you for your comments. Its not only a question of trading pair of
messages for an option-tag. Implicit subscriptions themselves are
problematic, as has been discussed on this list several times - the memo
provides for a method to suppress them, while being backwardly compatible.
If the UA receiving the REFER does not have to create the state information
for the subscription - then I see that as a distinct advantage

As for content push, there is no guarantee that the fetch happens
instantaneously - there could be the need for human interaction before that
happens. As for the attended transfer case, admittedly its a weaker example,
but in an enterprise setting - say between an employee, boss and secretary -
I see no need for the creation of additional messaging.

HTH,

Sriram

-----Original Message-----
From: Rohan Mahy [mailto:[email-masked]]
Sent: Monday, October 28, 2002 11:21 PM
To: Sriram Parameswar
Cc: [email-masked]
Subject: Re: [Sip] FW: New Draft - Suppression of Refer Implicit
Subscription

Hi,

thanks,
-rohan