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. Megaco/H.248 follows the guidelines published in RFC 2805 in April 2000, entitled Media Gateway Control Protocol Architecture and Requirements. The protocol performs the same functions as the Media Gateway Control Protocol (MGCP), is however a formal standard while MGCP has only informational status. Using different syntax and symbolic representation, the two protocols are not directly interoperable. They are both complementary to H.323 and the Session Initiation Protocol (SIP) protocols. H.248 was the result of collaboration of the MEGACO working group of the Internet Engineering Task Force (IETF) and the International Telecommunication Union Telecommunication Study Group 16. The IETF originally published the standard as RFC 3015, which was superseded by RFC 3525. The term Megaco is the IETF designation. Megaco combines concepts from MGCP and the Media Device Control Protocol (MDCP). MGCP originated from a combination of the Simple Gateway Control Protocol (SGCP) with the Internet Protocol Device Control (IPDC). After the ITU took responsibility of the protocol maintenance, the IETF reclassified its publications as historic in RFC 5125. The ITU has published three versions of H.248, the most recent in September 2005. H.248 encompasses not only the base protocol specification in H.248.1, but many extensions defined throughout the H.248 sub-series. Protocol overview H.248/Megaco due to its master-slave nature does not describe the establishment of calls across domains or across media gateway controllers. H.248/Megaco is used for communication downward, to the media gateways and does not constitute a complete system. The architecture requires other protocols for communication between multiple MGCs. The device that handles the call control function is referred to as an intelligent media gateway controller and the device that handles the media is referred to as a relatively unintelligent media gateway. H.248 defines the protocol for media gateway controllers to control media gateways for the support of multimedia streams across IP networks and the public