Subject: [Sipping] cc-transfer and app-interaction: providing a context for REFER

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 01 Feb 2005 02:03:09 -0500

Folks,

I was about to submit an update to the app-interaction framework, when I 
remembered that an issue came up at IETF 61 around the sipping 
cc-transfer draft that had potential impacts on app-interaction.

The issue, as you may recall, is how to do transfer with REFER on a 
separate dialog (routed using GRUU), and correlate that REFER to the 
dialog it would have otherwise been sent on. GRID was at first proposed, 
but then rejected. IIRC, this was because it require the UA to use a 
different, unique grid for every dialog it would ever set up, and that 
was incompatible with certain uses of grid, like creating a focus URI 
resident on a UA.

So, how to provide this correlation?

The app-interaction framework has already seen this problem, and has a 
solution documented there. The action item from the meeting was to make 
sure these were in sync.

The app-interaction framework defines a "context" parameter to Refer-To 
that includes the tags and call-id of the associated dialog. The 
semantics are that it is solely for authorization purposes. The 
existence of the context parameter with those values indicates that the 
REFERer has access to the dialog identifiers for the dialog. Thus, if 
the REFER authorization policy is based on whether it comes from someone 
with whom I am engaged in a dialog, it can be used for authorization 
purposes. Its semantics are no deeper than that.

I would propose that the current syntax and semantics defined in 
app-interaction suffice for the cc-transfer case. app-interaction is 
actually a SIP working item as it defines a new extension. Thus, 
cc-transfer could just reference it normatively and use it.

Comments?

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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---

From: David R Oran <[email-masked]>
Date: Tue, 1 Feb 2005 15:56:54 -0500

Works for me!
Dave.

On Feb 1, 2005, at 2:03 AM, Jonathan Rosenberg wrote:

> Folks,
>
> I was about to submit an update to the app-interaction framework, when 
> I remembered that an issue came up at IETF 61 around the sipping 
> dialog it would have otherwise been sent on. GRID was at first 
> proposed, but then rejected. IIRC, this was because it require the UA 
> to use a different, unique grid for every dialog it would ever set up, 
> and that was incompatible with certain uses of grid, like creating a 
> focus URI resident on a UA.
>
> solution documented there. The action item from the meeting was to 
> make sure these were in sync.
>
> The app-interaction framework defines a "context" parameter to 
> Refer-To that includes the tags and call-id of the associated dialog. 
> The semantics are that it is solely for authorization purposes. The 
> existence of the context parameter with those values indicates that 
> the REFERer has access to the dialog identifiers for the dialog. Thus, 
> if the REFER authorization policy is based on whether it comes from 
> someone with whom I am engaged in a dialog, it can be used for 
> authorization purposes. Its semantics are no deeper than that.
>
David R. Oran
Cisco Fellow
Cisco Systems
7 Ladyslipper Lane
Acton, MA 01720 USA
Tel: +1 978 264 2048
Email: [email-masked]

---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 16 Feb 2005 02:14:36 -0500

It seems like there is general consensus for this approach. As such, I 
have gone ahead and submitted an update to the framework. Until it 
appears in the archives, you can pick up a copy at:

http://www.jdrosen.net/papers/draft-ietf-sipping-app-interaction-framework-04.txt

This includes comments made during WGLC.

This document is now ready to go to IESG.

Thanks,
Jonathan R.