The Megaco protocol is used between elements of a physically decomposed multimedia gateway and is the result of cooperative efforts of the IETF and the ITU-T Study Group 16. The protocol definition of this protocol is common text with ITU-T Recommendation H.248. There are no functional differences from a system view between a decomposed gateway, with distributed sub-components potentially on more than one physical device, and a monolithic gateway such as described in H.246 . [para]The Packet network interfaces may include IP, ATM or possibly others, which support a variety of SCN signalling systems, including tone signalling, ISDN, ISUP, QSIG and GSM. National variants of these signalling systems are supported where ever applicable. Megaco also creates a broad framework suitable for gateways, multipoint control units and interactive voice response units (IVRs).