[SIPForum-discussion] B2BUA call flow.

[Xavi Milà]

Hi Sunitha,

the B2BUA concept as per RFC3261 [1] implies that a *new* request is
generated by the B2BUA acting as a UAC, establishing a new dialog, hence the
"outleg" you mention will contain a NEW Call-ID, different from the Call-ID
that appears in the "inleg". This is what I mean when I say that a B2BUA
splits the dialog. So, for a call flow where a B2BUA is involved -- like the
one you show -- this should be, as far as I know, the default behavior,
whenever you want and you need to change the Call-ID.

Regards,
-Xavi

[1] B2BUA definition in RFC3261

*
*

*Back-to-Back User Agent: A back-to-back user agent (B2BUA) is a logical
entity that receives a request and processes it as a user agent server
(UAS).  In order to determine how the request should be answered, it acts as
a user agent client (UAC) and generates requests.  Unlike a proxy server, it
maintains dialog state and must participate in all requests sent on the
dialogs it has established.  Since it is a concatenation of a UAC and UAS,
no explicit definitions are needed for its behavior.*


On Tue, Apr 12, 2011 at 1:25 PM, sunitha r <sunitha.samiksha at gmail.com>wrote:

> Hello Xavi,
> Thank you  for your response. But still i  need soem clarification.t.
> The call-id for inleg and outleg are same or different? please justify your
> answer.
> I wanted to setup the B2BUA call flow like this, what should be the call-id
> in Step(1),step(5),step(7).?
> A                      B2BUA           B
>         (1) INV Sdp A (inleg)
>         -------------->
>         (2) 200 Sdp B
>         <--------------
>         (3) ACK
>         --------------->
>         (4)      RTP
>         <---------------------->
>
>                                  (5) INV NO Sdp(outleg)
>                                  --------------->
>                                  (6) 200 Sdp C
>                                   <--------------
>         (7) ReINV Sdp C
>         <---------------
>         (8) 200 Sdp D
>         --------------->          (9) ACK Sdp D
>                                  ---------------->
>         (10) ACK
>         <---------------
>         (11)           RTP
>         <---------------------------------------->
>
> Regards,
> Sunitha.
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