Iñaki,
While many "pbx"s (including those from my employer) are implemented as
B2BUAs, it is possible to implement pbx functionality without a B2BUA.
(Dale and Scott can explain to you how they do it.)
Paul
Iñaki Baz Castillo wrote:
> 2008/9/23, karthik karthik <[EMAIL PROTECTED]>:
>> Hello,
>> Here is a question which I have for long time.
>> What is the prupose of having B2BUA?
>> I know that the B2BUA changes from tag,
>> callid and maintains a seperate dialog when to tag is received.
>>
>> But why it does change in these headers?
>> Some say it is for security reasons?
>> If yes how is it used for security. We also have NAT for security.
>>
>> Some say it is for manipulation of supplementary services. If yes,
>> cant a statefull proxy handle the services
>> without changing call-id, from tag and to tag?
>
> If you want to implement a PBX you need a B2BUA, not just a proxy.
> Imagine you want to redirect the call to other destination when the leg ends:
> - A calls B through a B2BUA.
> - B sends a BYE.
> - B2BUA receives the BYE and instead of sending a BYE to A it creates
> a new leg to C, so A speaks with C.
>
> This it not possible with a proxy (even if it's a call stateful proxy).
>
>
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