karthik,
B2BUA is a very general mechanism that may be used for a multitude of
purposes, some good, some evil.
Some things that are B2BUAs that you might not think of as such:
- a conference focus
- a presence server
The kind of B2BUA you seem to be talking about is probably an SBC, or
maybe a sip-pbx implemented as a B2BUA.
The SBC is typically there explicitly to interfere in / obfuscate the
signaling.
Sip pbxs are often implemented as B2BUAs because it gives a lot of
flexibility to the controller in the middle to handle the call "legs"
independently. Its often easier to deal with "dumb" phones that way.
In some cases a device that might otherwise be just a proxy must be a
B2BUA instead because it wants the option to inject messages into the
message stream between the two ends. For instance it may want to force
the termination of a call by sending BYE. A proxy cannot do that.
Thanks,
Paul
karthik karthik wrote:
> 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?
>
> Thanks Karthik Prabhu
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