H.248 (or Megaco)
H.248, also known as the "Megaco" protocol, is the international standard for media gateway control. It is a standard published jointly by the ITU and the IETF. It is primarily used to separate the call control logic from the media processing logic in a gateway. The device that handles the call control function is referred to as a Media Gateway Controller and the device that handles the media is referred to as a Media Gateway.
Refer to ITU-T H.323 Section 6.3.1 for a more complete description.