Subject: Re: [Insipid] disaggregated media: call origination

From: "Paul E. Jones" <[email-masked]>
Date: Tue, 9 Apr 2013 16:31:15 -0400

Charles,

> Perhaps this requirement needs be to expanded a bit to differentiate
> between proxies and B2BUA. For a proxy, in think the existing wording of
> Req 3 is fine. For a B2BUA, the requirement needs to be changed to state
> that 'M', in this example, remains unchanged rather than the entire
> identifier remains unchanged.

I don't think it's a matter of B2BUA vs. Proxy.  We want both to pass the
UUIDs along transparently.

However, the disaggregated media flow is a special case because the B2BUA is
acting like a gateway.  Basically, it's fully-terminating the SIP signaling
and originating new calls to both Bob's computer (Bc) and phone (Bp).  In
the flow Brett originally presented and the flow that James drew up, it
appeared to me that the B2BUA received a call from Alice, then initiated
communication with Bc and Bp.

Perhaps the "From" header going to both devices still said "Alice".  Perhaps
the Call-ID was the same, too.  However, if Bob's phone and computer
answered, what "tag" does the B2BUA send back to Alice?  Something Bc
returned or something Bp returned? Or something entirely different?  The
B2BUA has to make a choice.

As far as we could see, this call flow looked like a conference call where
the B2BUA was acting like a PBX/MCU/other.  It was "terminating" the call
from Alice and then inviting Bp and Bc into the conference.  Media would go
directly from Bp and Bc to Alice, perhaps, but it was clear that the B2BUA
was playing tricks with the signaling.

So, the call flow James prepared tried to address this special case.

Paul

---

From: "Charles Eckel (eckelcu)" <[email-masked]>
Date: Fri, 12 Apr 2013 19:20:45 +0000

Hi Paul,

I see the distinction you are making and I am fine with it. I agree that ideally a B2BUA should pass the UUIDs along transparently. I cases in which this is not possible, such as the disaggregated media case and the conference server case, we want the B2BUA/conference server to consistently use the same half key for itself.

Cheers,
Charles

-----Original Message-----
From: Paul E. Jones [mailto:[email-masked]] 
Sent: Tuesday, April 09, 2013 1:31 PM
To: Charles Eckel (eckelcu); 'Brett Tate'; James Polk (jmpolk); [email-masked]
Subject: RE: [Insipid] disaggregated media: call origination

Charles,

Paul