>>
>>                  |------ C
>>                  |
>>         A ------ B
>>                  |
>>                  |------ D
>>

> -----Original Message-----
> From: Paul Kyzivat [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, December 03, 2008 3:49 PM
>
> You mentioned something like "dialog-set". I'm not certain yet if "set"
> is the proper term here. But assume for the moment that it is.
>
> Then what you really have is a "dialog-set-id" right? Not a session-id.

I think very few people on this planet know what a SIP "dialog" is. :)
But the word "Session" is a more common word for operators (even though its 
definition in SIP is far more ambiguous, IMO).

For example, I think in your first 3PCC example (up top) most people really do 
expect that the same Session-ID be used for A-to-C.  Whether it should be the 
same for B-D is what (IMO) is fine but not necessary, but that's just my 
opinion; and I bet plenty of operators would consider that the same "Session" 
too and be surprised if it wasn't.


> (I suspect that an SBC creates
> dialog-sets, and other B2BUAs do not.)

I don't think so.  For example, I would argue that half the SIP functional 
roles defined in 3GPP create dialog-sets in actual deployment.  Or for example, 
what a find-me app server does, which hunts for a user at multiple targets; or 
even what a typical IP-PBX does; or what the market-leading "feature servers" 
seem to do.

Basically, my assertion is that if you receive a SIP request from A as a UAS, 
and route or fork it to one or more targets (B/C/D) as a UAC, you have created 
a single dialog-set.  Let's assume it establishes with B.  IF you receive an 
in-dialog or dialog-referential request from A or B, and act upon that request 
as the UA without forwarding it back to A or B and the action creates another 
dialog, (e.g., you create a new INVITE), then I'd argue you're probably 
creating a new dialog-set; because that's what should have been created had it 
actually gone back to A or B and they'd created a new dialog.  But really I'd 
defer to other people's opinions on that.

-hadriel
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