Call forking with early media

Applies to: Skype for Business 2015

An outgoing call can be forked to multiple endpoints. When an outgoing call is forked, the caller receives multiple provisional responses with response code 183 (Session Progress). A 183 response can contain an SDP body to establish an early dialog. In this case the SetAnswer(OfferAnswerContext, SdpOffer, SdpAnswer) method is invoked on the MediaProvider for each response. The CallDialogContext property represents the dialog context for the response.

When SetAnswer is invoked for a Provisional answer, the Status property will be SdpAnswerStatus.Provisional. After the call receives the final 200 OK response, the SetAnswer method is invoked with the final answer. In this case the CallDialogContext property on the OfferAnswerContext instance represents the final confirmed dialog and Status property will be SdpAnswerStatus.Final.