Gateway Control Protocol

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The Gateway Control Protocol, also known as Megaco (IETF designation) or H.248 (ITU designation), is a control protocol used between a Media Gateway and a Media Gateway Controller in a network. It defines the necessary control mechanism to allow a Media Gateway Controller to control gateways in order to support multimedia streams across networks. It is typically used to provide VoIP functionality (including voice/fax calls) between PSTN-IP or IP-IP networks.

The protocol was the result of joint work of the IETF's MEGACO working group and the ITU's ITU-T Study Group 16. It is defined by ITU-T Recommendation H.248.1. The IETF also originally published the standard (as RFC 3015, and later replaced by RFC 3525) but the ITU has now taken ownership of the protocol and IETF's version has been reclassified as historic. The ITU has published three versions of H.248.1, 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.

It is important to note that while used over the same interface and similar in functionality, H.248 is a completely different protocol from MGCP and the underlying differences make them incompatible with each other.

[edit] See also

• ITU-T H-series Recommendations ITU-T Publication site where the H-series, including the H.248 Sub-series, Recommendations can be downloaded in PDF format free of charge.
• H.248 Information Site This site provides information related to H.248, including pointers to standards and draft specifications
• Media Gateway Control Protocol (MGCP)
• Session Initiation Protocol (SIP)
• H.323