Paul,
  Appreciate the details u have put across... yes B2BUA is loosely defined... 
with different interpretations..
  I agree with .. >>It does'tn have to do MEDIA  but >> I am not very clear as 
to why u say it does'nt have to initiate a new call.. or answer calls..
 
 B'cos as per what it stands for (Back-2-Back-UA)... which means for UAC is 
will act as a UAS.. so ansering that call,,and for the actual UAS... it will 
behave as a UAC,,and so originating the new call,,
 
 I would think of B2BUA as some1 who bridges both ends (UA's) simialr to a 
proxy, but both legs being different calls.. so that B2BUA has control over the 
call.. for billing purpose etc,,if it intends to broker other services ...and 
present collated billing to say the Softswitch..etc.. or whatever application 
one intends to build it for.
 
 Can you also talk more about. Is this comment for the same context...
- conference focus
- message exploder
 
 
Rama




Paul Kyzivat <[EMAIL PROTECTED]> wrote:
Amarendra,

The term B2BUA is very general, and implies very little. It has only 
one responsibility: to act as a UA, in each direction that it faces.
- It isn't required to initiate calls at all.
- It isn't required to answer calls directed at it.
- It isn't required to do anything with media.

Almost everyone that asks questions about B2BUAs has something more 
specific in mind - something that is a specialization of a B2BUA with 
some specific intent in mind.

There are a few kinds of things that are being standardized by the IETF 
that happen to be UAs:
- conference focus
- message exploder

Another thing that is under discussion, and that is loosely understood, 
is a Session Border Controller. (I say loosely understood because you 
will probably get a different set of detailed requirements from each 
person you ask.) In most incarnations an SBC is a B2BUA.

Some "SIP PBXs" and SIP SoftSwitches are implemented as B2BUAs, though 
there is no standards for this.

The 3GPP IMS specifications define various CSCFs that sometimes may 
behave as B2BUAs.

Each of these things has its own behavior. If it is one of these things 
that you are interested in, then there may be an answer to your 
question. But you are asking your questions about B2BUAs in general 
there is no answer.

Paul


Amarendra Kumar wrote:
> Hi,
> 
> Is it the responsibility of the B2BUA establish call even if both the
> end pionts don't
> have compatible media codecs. 
> Lets say : A is trying to reach B, But both of them, don't have
> compatible media
> codecs. 
> 
> While connecting A & B, can B2B terminate one callleg (ie. A --- B2B) at B2B
> and start one more (ie. B2B-------B), also B2B will do the codec conversion 
> for 
> imcompatible codecs. In this senario there will be be 2 RTP sessions
> established for the single call. If so then which is the best place
> for the codec
> converter
> 1. Along with B2B
> 2. Independent entity (application server) which will handle all
> media related stuff
> 
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