RFC 3911 would help to address this scenario, although Cisco 7960 does not implement the RFC (I wonder which UACs do?). Alexander.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Aaron Clauson Sent: Wednesday, August 17, 2011 6:31 AM To: [email protected] Subject: Re: [Sip-implementors] Initiate 3-Way Call > -----Original Message----- > From: Worley, Dale R (Dale) [mailto:[email protected]] > Sent: Tuesday, 16 August 2011 1:56 AM > To: Aaron Clauson; [email protected] > Subject: RE: [Sip-implementors] Initiate 3-Way Call >> From: Aaron Clauson [[email protected]] >> >> I've had a request from a user wanting to be able to initiate a 3 way call >> from my B2BUA. I don't do any media handling on my B2BUA so employing a >> server side audio mixer or such is not an option. > Your description is sort of confusing because you don't have a > consistent terminology for the various SIP dialogs (legs). I did intentionally avoid talking about the scenario in terms of dialogs as I was thinking there may have been some obscure way to get a 3 way call set up in one fell swoop. Maybe a 3PCC RFC somewhere. However I think I'm clutching at straws on that one. > But as a general observation, it's difficult to alter the actual > remote end of the media without starting a new SIP dialog, due to the > strict rules regarding what updates can be made to the SDP of an > existing dialog. In this case I wouldn't need to change the remote end of the media. In terms of dialogs the scenario would be: 1. Alice places call to B2BUA which initiates two independent calls to Bob & Charlie, 2. Bob answers and a dialog 1 is established between Alive and Bob, 3. Sometime later Charlie answers and dialog 2 is established between Alice and Charlie. Alice's phone has an audio mixer capability so is able to handle two independent media streams. My problem is I don't know of any SIP mechanism to do step 3. Once the INVITE transaction initiated by Alice is answered there's no way to send get Alice's phone to create the 2nd dialog with Charlie. The way it could be done is: 1. Alice places call to B2BUA which initiates a call to Bob, 2. Bob answers and a dialog 1 is established between Alive and Bob, 3. The B2BUA initiates a call to Alice and when she answers, putting Bob on hold, the B2BUA initiates a call to Charlie, 4. Charlie answers and a dialog 2 is established between Alive and Charlie, 5. Alice hits the 3 way call button on her phone (on a Cisco 7960 the menu option is Conf) and the media streams from the two dialogs are combined in the audio mixer and the 3 way call proceeds. The problem with that approach is step 3 where Alice is waiting for Charlie to answer when she would most likely prefer to be speaking to Bob. Aaron _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
