responses inline...

Tanmay Zargar wrote:
>
> Hello all,
> I have some doubts regarding a SIP B2BUA.
>
> The B2BUA is defined as a virtual UAS/UAC connected back to back.
> It differs from a SIP proxy in that it can originate requests apart
> from ACK and CANCEL. Also, the B2BUA is supposed to provide the
> interface to call-control/service logic - eg. to an external
> media/application server.
>
> I want to know if the SIP B2BUA can itself be an end point like a
> normal UA?

Yes, it is an endpoint on two call legs, UAS on one and a UAC on the other.

> Is the functionality of the B2BUA the same as that of the normal UA?
> Does it have to be call/dialog stateful?

Yes, it follows the rules defined for a UAS on one call leg and follows the
rules for a UAC on the other call leg.

> Is there any document/draft that specifies the behaviour of a SIP
> B2BUA - particularly its interface with the application
> server and how
> it can be used as a 3PCC service execution controller?

The sip-3pcc draft below is a good one.  But these drafts don't define the
"B2BUA" specifically.  It's just a UAS-UAC, which is defined in the base SIP
specification.  The peer-3pcc draft takes a little different approach,
showing how a UA itself can do interesting things vs. a "controller
platform" handling many calls at a time.

>
> I have gone through a few drafts (listed below) on 3PCC but
> there is no
> information on the architecture/functionality/interface of the B2BUA
> with the application server.
>
> http://www.cs.ru.ac.za/research/g9610645/sip/draft-ietf-sip-service-
> examples-01.txt
> http://www.ietf.org/internet-drafts/draft-mahy-sip-cc-models-01.txt
> http://www.cs.columbia.edu/sip/drafts/draft-mahy-sip-peer-3pcc-00.txt
> http://www.globecom.net/ietf/draft/draft-culpepper-sip-key-events-
> 00.html#6
> http://iptel.org/info/players/ietf/callprocessing/draft-rosenberg-sip-
> 3pcc-03.txt
>
> I would appreciate if anyone could provide me with any
> answers/clarifications/leads to the above.

The point is, some services in the PSTN for example can be supported in SIP
networks using some clever application of SIP UAC/UAS behavior.  B2BUAs are
just one approach though, depending on the service there may be better
approaches.

Regards,
Bert

> Thanks,
> Tanmay.
>
>

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