Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP

Cullen Jennings <fluffy@iii.ca> Thu, 10 May 2012 22:47 UTC

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From: Cullen Jennings <fluffy@iii.ca>
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Date: Thu, 10 May 2012 16:47:50 -0600
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To: Martin Thomson <martin.thomson@gmail.com>
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Cc: Randell Jesup <randell-ietf@jesup.org>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP
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On May 10, 2012, at 3:07 PM, Martin Thomson wrote:

> On 10 May 2012 13:56, Cullen Jennings <fluffy@iii.ca> wrote:
>> I was looking more for the actually sort of end user use case where this might happen.
> 
> I ring you.
> Your mobile and home phone both ring.
> You answer your mobile, your daughter answers the home phone.
> I get to talk to both of you.
> 
> Of course, that's not such a great outcome.  I can hear both of you,
> but you can't hear each other unless I have really bad echo
> cancellation.
> 
> I tend to think of this as solving a really interesting signaling
> problem that doesn't really have any practical application.  If you
> want to talk to both people, then you should signal the creation of a
> conference call.
> 
> --Martin

That an good use cases, except the people need to be able to hear each other. It gets called lots of things but some PBXs call it bridged line appearance. Variation of it have been discussed in bliss and draft-ietf-bliss-shared-appearances. It really comes down to where you think the conferencing should happen. If it does not happened on the the callers phone, seems like existing jsep idea should be able to do this.  (given the callee is the phone that is most likely out of administrative control of the other two phones that set up bridged line a appearance, assuming that phone can and is willing to do the conferencing seems like a bad architecture for this problem). Again lot of systems do this today in SIP and seem to do it without needing forcing the callers phones to deal with multiple simultaneous calls signaled in some way I don't even know how to signal in SIP.