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Re: [Sip] B2BUA question.



Some of my opinion below.  I agree that there is a need for some common
understanding of B2BUA.  Perhaps an informational I-D is in order.
Eric

"Kaul, Amit" wrote:
> 
> I agree that we might want to limit our discussion only within SIP
> properties
> of B2BUA to get some common understanding of B2BUA as a SIP logical entity.
> 
> In addition to few queries which Chinmay has pointed out,I can think of
> some basic points that need to be clarified/discussed about B2BUA :
> 
>    - Can B2BUA behave as a forwarding agent like Proxy, witout initiating
>      a new dialog ?

No.  Remember B2BUA, Proxy etc are logical entity.  A physical
implementation (say call it a SIP server) may be a combination of a
B2BUA and a Proxy, and an INVITE may be handled by the Proxy part.

> 
>    - Can B2BUA decide to Fork like a Proxy ?

A B2BUA can certainly make 2 outbound calls on receipt of 1 incoming
call.  But the call flow is different from a Proxy e.g. Chinmay scenario
2
> 
>    - Can B2BUA decide to switch between UAC/UAS and Proxy functionality like
> 
>      Proxy and Redirect functionality.
As above, a SIP server that implements the B2BUA, Proxy and Redirect
server logical entities can do this.
> 
>    - Is it mandatory for B2BUA to be always call-stateful ?

Yes, I think so.
> 
>    - Since a UA can be stateless (RFC3261 Sec 8.2.7), is stateless B2BUA
>      also possible ?

The UAS part of a B2BUA can behave in the way describe in sec 8.2.7 to
challenge unauthenticated requests.

> 
>    - Finally, can B2BUA be called as a combination of "Proxy and UAS/UAC"
>      or just "UAS/UAC" combo ?

See above.  I think it is cleaner to keep the logical entities as clean
as possible.
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