The Gateway Control Protocol (Megaco, H.248) is an implementation of the media gateway control protocol architecture for providing telecommunication services across a converged internetwork consisting of the traditional public switched telephone network (PSTN) and modern packet networks, such as the Internet.

H.248 is the designation of the recommendations developed by the ITU Telecommunication Standardization Sector (ITU-T) and Megaco is a contraction of media gateway control protocol used by the earliest specifications by the Internet Engineering Task Force (IETF).

The standard published in March 2013 by ITU-T is entitled H.248.1: Gateway control protocol: Version 3.

[1] Megaco/H.248 follows the guidelines published in RFC 2805 in April 2000, entitled Media Gateway Control Protocol Architecture and Requirements.

Megaco combines concepts from MGCP and the Media Device Control Protocol (MDCP).

H.248/Megaco due to its master-slave nature does not describe the establishment of calls across domains or across media gateway controllers.

Although the modeling of the Media Gateway differs in H.248/Megaco when compared to MGCP, there is a similarity between the semantics of the commands in the two specifications.

Message {Transaction {Action {Context {Command {Termination {Descriptor {Package}}}}}}} By analogy with the OSI model, the hierarchy of interworking levels from the point of view of transmission over the network (Ethernet or ATM) is following.

In case o MGCP, however, the MGC needs to establish several connections to a special type of endpoint called the conference bridge.