Re: [splices] Using Two Separate Devices to Start a Conversation proposal

"Worley, Dale R (Dale)" <> Thu, 30 June 2011 22:06 UTC

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From: "Worley, Dale R (Dale)" <>
To: Gonzalo Camarillo <>, Alan Johnston <>
Date: Thu, 30 Jun 2011 18:06:38 -0400
Thread-Topic: [splices] Using Two Separate Devices to Start a Conversation proposal
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Subject: Re: [splices] Using Two Separate Devices to Start a Conversation proposal
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>> As Dale mentioned, this also depends on the other end doing the "right
>> thing" with this case. It is a leap of faith to assume it will realize it
>> should accept both streams and use one for input and the other for output.
>> ISTM its at least as likely that it would accept the first stream, reject
>> the second, and then have only a one-way "conversation".
> OK, I understand the problem right now.  The problem is that this is a
> special kind of "Join" operation.  It is kind of a join, but not
> quite.
> The operation we are after is perhaps similar to 3.3.8 Far-Fork in RFC 5850:
> I suspect instead of Join, we need a new primitive, lets call it
> Splice or Merge which requests the UAS to add the media in the INVITE
> into the dialog that is referenced.

OK, now I see the problem with using Join.

UA A1 sends an INVITE (requesting only audio) to UA B (which supports
both audio and video).

UA A2 sends an INVITE (requesting only video) to UA B (which supports
both audio and video), with Join to the first dialog.

Then we should expect that UA B will send its audio to A1 and its
video to A2, within the semantics of Join.

The difficulty is that UA B still sees the situation as two different
dialogs.  E.g., if A1 sends a REFER/Refer-To: C to B, the A1-B dialog
will be replaced by the C-B dialog, but the A2-B dialog will be

Which is not the behavior we want if we are trying to logically bond
A1 and A2 to act as a single UA.

Using Join would have been convenient as it is already defined, and
theoretically, UAs already support it.