Patent ID: 7912042

Claim:
A method in a telecommunication system of facilitating communications between a first terminal A configured to use a first session model wherein two media sessions are negotiated and set up as one signaling session, and a second terminal B configured to use a second session model wherein two media sessions are set up in parallel as a first media session for voice and a second media session for video, said method comprising the steps of: registering a first IP Multimedia Telephony (MMtel) feature tag in a Call/Session Control Function associated with the second terminal B (CSCF-B) in a control domain in the system, the first feature tag representing a contact between the first terminal A and the second terminal B; initiating setup of the voice media session between the first and second terminals; detecting the registered first MMtel feature tag, wherein the first MMtel feature tag indicates that the voice media session must be routed through a circuit-switched domain for the terminals to be able to communicate; and routing the voice media session via the circuit-switched domain.