Other signaling protocols include Media Gateway Control Protocol (MGCP) and Media Gateway Control (MeGaCo). These are just two examples, and I will briefly touch upon the two of these.
The Media Gateway Control Protocol is a merger of the Internet Protocol Device Control (IPDC) and the Signal Gateway Control Protocol (SGCP). It very closely resembles SIP functionality. IDPC is a suite of protocols that can, individually or together, perform connection, control, media control, and signaling transports between the circuit-switched network and the Internet. Signal Gateway Control Protocol (SGCP) is a UDP-based protocol designed to address the concept of a network that combines voice and data onto a single packet-switched IP network operating at a low level. There are two main components of a MGCP, the Call Agent and the Gateway. MGCP uses SDP to negotiate media streams and frames the media streams using RTP.
Megaco is a separate implementation of the Media Gateway Control Protocol. It is designed for controlling Media Gateways on IP networks and the PSTN. It provides voice over IP and faxing services between IP networks and PSTN. It is a joint project from both the IETF and the ITU. MegaCo is also known as H.248.