Subject: RE: [Sip] B2BUA

From: "Drage, Keith (Keith)" <[email-masked]>
Date: Mon, 9 Dec 2002 15:41:46 -0000

I would suggest that in addition to this, we list in this proposed informational document Deans 10 rules of transparency (suitably enhanced if necessary). B2BUA providers can then use this as a tick list to indicate some of the functionality of the B2BUA, and receivers of such a list will get an idea of how significantly the entity breaks the end-to-end SIP transparency, which is after all the main thing of interest to the end UA.

Doing this may actually provide a document of some use, and allow IETF to put forward that even if it is a B2BUA, designing as much transparency into it, while still performing the un-proxy-like function that is intended, is a good thing.

Keith

Keith Drage
Lucent Technologies
Tel: +44 1793 776249
Email: [email-masked] 

> -----Original Message-----
> From: Rosen, Brian [mailto:[email-masked]]
> Sent: 03 December 2002 16:29
> To: [email-masked]'
> Cc: [email-masked]
> Subject: RE: [Sip] B2BUA
> 
> 
>  
> > So the B2BUA is a concatenation of two User Agents, each of 
> > which acts both as UAC and UAS. A conference server will 
> > probably look like a UA, definitely not a B2BUA, IMHO.
> >    
> This thread is, hopefully reaching an end (with an agreement to
> do some examples with call flows).  However, the above statement
> is yet one more example of the confusion people have with B2BUA.
> 
> The key thing about a B2BUA is that it looks like a UA to whatever
> it is connected to (on both sides).  So, a conference server
> looks like a UA to each of it's ports, and it has at least two of
> them, and there is some "magic" between them.  If you look at the
> concept of the "focus" from the conferencing work, it is a
> thing that has a bunch of two ended SIP calls, one with each
> participant.  Each participant thinks it is talking to a UA.
> While some messages sent from a participant to a UA might be
> consumed by the UA (state changes), often, a message will trigger
> messages from the focus to other participants.
> 
> This seems, to me, to meet the definition of B2BUA in 3261,
> and more strongly meets proposed changes in the definition.
> Of course, it really doesn't matter if you consider the focus to
> be a B2BUA or not.
> 
> Brian 
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