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==Network elements==
===Media gateway===
A [[media gateway]] is a device that converts media streams in the form of digital data or analog signals in telecommunication for services such as voice, video, and fax applications between two, usually dissimilar, interfaces using different technologies. One of the technologies usually is a [[packet switching|packet]], frame, or [[cellular network|cell]] network.<ref name=rfc2805 /> For example, it may convert voice telephone calls between a traditional analog [[telephone]] to a digital format for transmission over an [[Internet Protocol]] (IP) network, to facilitate [[voice over IP]] communications.
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In July 1998, Telcordia (Bellcore) and [[Cisco Systems]] created a protocol called [[Simple Gateway Control Protocol|Simple Gateway Control Protocol (SGCP)]] for controlling Telephony Gateways from external call control elements.<ref name=SGCP>{{cite web|title=Simple Gateway Control Protocol (SGCP|url=http://tools.ietf.org/html/draft-huitema-sgcp-v1-01|publisher=IETF|date=30 July 1998|accessdate=8 June 2012}}</ref>
Meanwhile, in mid-1998, Level 3 created a Technical Advisory Council (TAC), composed of a dozen leading communications equipment manufacturers. The TAC proposed a device protocol called [[Internet Protocol Device Control]] (IPDC) in August 1998.<ref name=IPDC>{{cite web|title=IPDC - Connection Control Protocol|url=http://tools.ietf.org/html/draft-dugan-ipdc-connection-00|publisher=IETF|date=August 1998|accessdate=8 June 2012}}</ref> IPDC was intended to used between a media gateway and a media gateway controller. Media gateway were capable of acting as a voice over IP gateway, voice over ATM gateway, dialup modem media gateway, circuit switch, or cross- connect. In October 1998, [[Simple Gateway Control Protocol]] (SGCP) was combined with [[Internet Protocol Device Control]] (IPDC), resulting in MGCP.<ref name=merger>{{cite web|title=Level 3 Communications, Bellcore Announce Merger of Protocol Specifications for Voice Over IPe|url=http://level3.mediaroom.com/index.php?s=23600&item=65733|publisher=Level 3 Communications|accessdate=8 June 2012}}</ref>
MGCP was submitted to the [[IETF]]’s MeGaCo working group in October 1998.<ref name=MGCp-01>{{cite web|title=Media Gateway Control Protocol (MGCP)|url=http://tools.ietf.org/html/draft-huitema-MGCP-v0r1-00|publisher=IETF|date=27 October 1998|accessdate=8 June 2012}}</ref> In November 1998, [[Lucent]] Technologies submitted a draft for third device protocol, called [[Media Device Control Protocol]] (MDCP) to used by media gateways and their controllers.<ref name=MDCP>{{cite web|title=Toward the PSTN/Internet Inter-Networking - MEDIA DEVICE CONTROL PROTOCOL|url=http://tools.ietf.org/html/draft-sijben-megaco-mdcp-00|publisher=IETF|date=November 1998|accessdate=8 June 2012}}</ref> IETF merged MGCP and MDCP and proposed a new and improved protocol named MeGaCo protocol (also known as H.248) in April 1999.<ref name=MEGACO>{{cite web|title=MEGACO Protocol|url=http://tools.ietf.org/html/draft-ietf-megaco-protocol-01|publisher=IETF|date=16 April 1999|accessdate=8 June 2012}}</ref>
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