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Re: [Sip] B2BUA question.



Some comments re scenario 2 inline.

Eric

> Scenario 2 -
> 
>         I am not sure if this part of the email belongs here or in the implementers list. Let me know if I should move this part of the email to the implementers list.
> 
> UA1                     B2BUA                   UA2             UA3
> |-- INVITE -------> |                    |                |
> |       CID:1             | -- INVITE ---->|              |
> |                         |     CID:2          |                  |
> |                         |                  |            |
> |                         | -- INVITE ----------------->|
> |                         |     CID:3            |                |
> |                         |                      |                |
> |                         | <-- 200 OK --- |              |
> | <---- 200 OK ---- |                    |                |
> |                         | <-- 200 OK -----------------|
> | <----- 200 OK --- |                    |                |
>         ?????????
>         Can this be forwarded.
> 
> In this scenario the B2BUA, on receiving the INVITE request from UA1, generates new INVITE request to two UAs, UA2 and UA3. (A similar scenario will occur if a downstream proxy forks and receives multiple 200 OKs.)
> 
> - Can the B2BUA generate two INVITE/Requests, for one incoming INVITE/Request? Is this allowed by the protocol/definition of B2BUA?
> 
> IMO this should be allowed.

Yes, this is allowed.  The B2BUA at this point would look like:

|----|-----|
|    | UAC |
|UAS |-----|
|    | UAC |
|----|-----|

> 
> Now both the UAs respond with 200 OK responses.
> 
> - Is the B2BUA allowed to generate two responses towards UA1 (with different to-tags)?
> 
> IMO this also should be allowed.

No, I don't think this is allowed.  These are 3 completely distinct SIP
dialogs.  In fact, the 200 OK sent by UAS to UA1 should have a different
to-tag from the to-tag received from UA2 and UA3.
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