media gateway control protocol (NGN) (MEGACO)
The MediaGateway Control Protocol (MEGACO) is a gateway protocol supported by the Internet Engineering Task Force( IETF) and the International Telecommunication Union( ITU) under H.248 for controlling media gateways( MGW). It works independently of call signaling with H.323 and the Session Initiation Protocol( SIP) and is used to establish VoIP connections.
The Megaco/H.248 has the functions of the MGCP protocol combined with the Media Device Control Protocol( MDCP). It works in master- slave mode, where the master is formed by a softswitch and the slaves by the media gateways, and supports the necessary control functions of the IP phones. In addition, the protocol has peer-to-peer interoperability. It decomposes the H.323 function into subcomponents and specifies the protocols used by each component for the respective communication processes. The softswitch exchanges information with the signaling gateway( SGW), which receives information from the telephone network via, for example, SS7 signaling, two-tone(DTMF), or Q-Interface Signalling Protocol( QSIG). This ISUP information is converted in the softswitch and is used to control the media gateways to which the VoIP telephones are connected.
With Megaco, only the important messages are fixed in the basic protocol. Manufacturer-specific extensions are easy to integrate. The Megaco protocol can also be used in conjunction with other packet- or cell-switched networks such as ATM.
Megaco is described in RFC 3015.