Subject: [SIP] 3PCC and REFER method

From: <Javier_Ferreiro_Garcia/UT03329/PLATAFORMAS_DE_SERVICIOS/[email-masked]>
Date: Fri, 29 Dec 2000 11:59:43 +0100

Hi
I would like to open again the issue discussed in
http://lists.bell-labs.com/pipermail/sip/2000q4/004739.html

>>What happens when there is not an active SIP (INVITE) session between the
>>referer and referee ? Sending an INVITE in this case may have unwanted
>>effects (like initiating a call). Are you proposing that either a) you
would
>>only send the INVITE/BYE if a corresponding SIP (INVITE) sessions exists
or
>>b) that REFERS are not allowed outside of a SIP session?

>  What does a REFER outside of a session mean?

and apply this idea to the scenario proposed in
draft-rosenberg-sip-3pcc-01.txt Figure 1 and specifically the
example included for Click-to-dial application.

In this alternative scenario for Click-to-dial, the controller, after
receiving the request via HTTP, do not INVITE both A and B, but rather send
a REFER to A, asking A to INVITE the CONTROLER ITSELF. When the controller
receives the INVITE SDP A from A, checks in its internal database who is
supposed to be contacted by A (in this case B) and sends INVITE SDP A to B.
In this case I think the re-INVITE loop could be avoided by  applying this
scenario which is more similar to a normal INVITE between two parties.

In this alternative scenario the referer (i.e. the controller) and the
referee (i.e. the web-surfer) are OUTSIDE of a SIP session, but INSIDE an
HTTP session. It could also be decided the referee to be the IP phone from
the customer service representative, if the web-surfer IP phone either does
not support REFER or is a PSTN endpoint.

The reason to include as content of Refer-To header not B but the
controller itself is to let the controller do its job in a more general way
(i.e. imagine click-to-dial + mid-call-announcement)

If the scenario is not the one described for Click-to-dial, but for Mid
Call AnnouncementCapability, the controller does not either set up the call
to A or send the REFER method to A, but rather receive the INVITE from A
and act as a "termination and reinitiation point" for control purposes
(i.e. disconnect and reconnect A to a media server under certain
conditions) as defined in draft-rosenberg-sip-3pcc-01.txt

Sorry if someone has already suggested this and I have missed it...
Comments?

-----------------------------< O >-----------------------------------
Javier Ferreiro Garcia
Consultant
Telefonica Moviles Spain
Dpto. de Plataformas de Servicios
3rd Generation Intelligent Network Platforms
    Telf.: +34 630 00 43 13
-----------------------------< O >-----------------------------------

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