[reSIProcate-users] About the ACK - B2BUA scenario

["jcabezas" <jcabezas@xxxxxxxxxx>]

Hi,

      Recently, Scott Godin explained that ACK won´t be sent automatically by DUM if an SDP answer is needed, and the onOffer callback would be the chance to the application supply the needed SDP via provideAnswer, and only then DUM will send  ACK.
      In a B2BUA scenario the required SDP answer won´t be available until the application sends to the other side a 200 OK with the received  SDP offer and then, after getting from that other side an ACK with the SDP answer, the app can call onProvideAnswer wit the right SDP answer.

 

     Alice      [DUM-based B2BUA app]    Bob
        |                ||                |
        |                ||                |
        |                || 200 OK (offer) |
        |                ||<---------------|
        | 200 OK (offer) ||                |
        |<---------------||                |
        | ACK (answer)   ||                |
        |--------------->||                |
        |                || ACK (answer)   |
        |                ||--------------->|
        |                ||                |
        |                ||                |

 

      Just to double-check:  DUM will withhold for an undefined time ACK transmission until application invokes ProvideAnswer and (what is crucial too), ProvideAnswer does not need to be invoked inside the scope of onOffer callback, but outside and later ? 
Is it right ?

Julio Cabezas.