Subject: [Sip] Change of display name

From: Jean-Francois Rey <[email-masked]>
Date: Wed, 01 Oct 2003 11:53:00 +0200

I'm implementing some attended transfer use cases between a telephone 
gateway and SIP phones. I need to update the display name when the 
transfer takes place. Unfortunately, if more than one gateway is 
involved in the transfer, I cannot use the REFER + replaces mechanism. I 
know that this topic has already been discussed in this list : Update of 
display name during a call 
(http://www1.ietf.org/mail-archive/working-groups/sip/current/msg08521.html), 
Update and P-Asserted-ID 
(http://www1.ietf.org/mail-archive/working-groups/sip/current/msg08142.html). 
Unfortunately, I'm still a bit unsure of what is the outcome of these 
threads. Using an identity mechanism (a short term one like 
P-Asserted-ID or a long term one like AIB) in a UPDATE or re-INVITE 
seems a bit underspecified to say the least. Could anyone provide 
guidance on these topics : do we have a consensus ? Would this consensus 
go beyond telephone gateways experts and include SIP phone and 
application vendors ? Are there any existing documents or planned 
actions (new versions of drafts or rfcs, BCP) that would clarify this 
topic ?

I played a little bit with SIP phones and I found out that a solution 
works with many SIP phones : using the usual INVITE + replaces mechanisms.

So instead of the UPDATE + identity solution

          Gateway	 Dialog D1	    SIP phone
	  |=========================|
	  |    (D1)UPDATE	    |
	  |------------------------>|

I tried this :

          Gateway	 Dialog D1	    SIP phone
	  |=========================|
	  |    (D2)INVITE	    |
	  |	(replaces D1)	    |
	  |------------------------>|

It works fine except if D1 is not confirmed.
I understand that
- there might be GRUU/routing problems (but nothing new compared to 
usual REFER + replaces mechanism),
- there are more messages being exchanged than in the UPDATE solution 
(but the INVITE + replaces seems the BCP for attended transfer in SIP).

So there are issues. OTOH this solution works with many implementations, 
it can rely on all identity solutions and IMHO it uses nicely the 
semantic of replaces (which is needed for attended transfer between SIP 
phones anyway).

I'd like to have the community's feeling on that topic.

Thanks,
Jean-Francois

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: "Venkatesh Venkataramanan" <[email-masked]>
Date: Thu, 9 Oct 2003 11:48:00 -0700

We had attempted to capture enabling calling/called party display name in
http://www.ietf.org/internet-drafts/draft-venkatar-sipping-called-name-00.txt . 

The draft proposed using the P-Asserted-Identity header in UPDATE, REFER and SIP response messages to update the calling and the called UA displays of name changes. 

Regards,
Venkatesh

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Jonathan Rosenberg
Sent: Thursday, October 09, 2003 11:31 AM
To: Elwell, John
Cc: Jean-Francois Rey; [email-masked]
Subject: Re: [Sip] Change of display name

I tend to think it makes sense to be able to update a bunch of SIP 
related state through an UPDATE request. This is beyond the currently 
documented scope of UPDATE, though certainly the intent was to allow 
it. Indeed, the original drafts on UPDATE described its usage to solve 
the "HERFP" problem, whereby an UPDATE was used to change credentials, 
require header values, etc., after the initial INVITE. This aspect of 
UPDATE was removed from the main spec because it was less stable, and 
we needed UPDATE for other, more pressing things. However, I have not 
had the time to follow through and revive those yanked portions of 
UPDATE. Presumably such a draft would cover the ability to change 
P-Asserted-ID and other things as well. Volunteers to revive this draft?

-Jonathan R.

Elwell, John wrote:

> Jean-Francois,
> 
> I thought the earlier thread to which you refer was leaning towards the use
> of UPDATE or re-INVITE with revised identity information. A related thread
> was started by Cullen Jennings on 29th August ("Update of display name
> during a call"), proposing the use of a revised display name in a From/To
> header inside an AIB in an UPDATE or re-INVITE request. The thread led to
> the related question of whether a revised P-Asserted-ID header could be
> included in an UPDATE or re-INVITE request, but this appeared to be
> inconclusive.
> 
> John ([email-masked])
> 
> 
> 
>>-----Original Message-----
>>From: Jean-Francois Rey [mailto:[email-masked]] 
>>Sent: 01 October 2003 10:53
>>To: [email-masked]
>>Subject: [Sip] Change of display name
>>
>>

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

---

From: "Elwell, John" <[email-masked]>
Date: Fri, 10 Oct 2003 13:20:41 +0100

Venkatesh,

This may well be of interest, but to solve the problem raised at the start
of this thread I would also like to see P-Asserted-ID in an UPDATE or
re-INVITE request.

> From: Venkatesh Venkataramanan 
> [mailto:[email-masked]] 
> Sent: 09 October 2003 19:48
> To: Jonathan Rosenberg; Elwell, John
> Subject: RE: [Sip] Change of display name
> 
> 
> The draft proposed using the P-Asserted-Identity header in 
> UPDATE, REFER and SIP response messages to update the calling 
> and the called UA displays of name changes. 
> 
> Regards,
> Venkatesh
> 
> >>From: Jean-Francois Rey 
> [mailto:[email-masked]]

---

From: "Venkatesh Venkataramanan" <[email-masked]>
Date: Fri, 10 Oct 2003 11:09:53 -0700

John:

The discussion at the start of the thread is one of the requirements we attempted to solve as a part of this draft (last bullet item mentioned in the Requirements section of this draft is to do with updating displays in call scenarios like transfers, retrieving a parked call and features of that nature). 

The modified table for P-Asserted-Identity header in this draft, makes the header optional in a SIP UPDATE request (enabling this header in this request was to satisfy the last requirement). We ended up focusing on its usage in a SIP response. We should have added content to clarify how we addressed the last requirement and why the draft proposed enabling the header in a SIP UPDATE request.

Regards,
Venkatesh

-----Original Message-----
From: Elwell, John [mailto:[email-masked]]
Sent: Friday, October 10, 2003 5:21 AM
To: Venkatesh Venkataramanan; Jonathan Rosenberg
Cc: Jean-Francois Rey; [email-masked]
Subject: RE: [Sip] Change of display name

Venkatesh,