Megaco

from Wikipedia, the free encyclopedia

Megaco (short for Media Gateway Control ) is a gateway protocol developed jointly by the IETF ( RFC 3015 , later RFC 3525 ) and the ITU-T (Recommendation H.248) for controlling media gateways (MG) and is used for the construction used by VoIP connections. It works independently of signaling protocols such as the network protocol H.323 and the Session Initiation Protocol (SIP). It mainly supports signaling from the SIGTRAN group of the IETF and provides voice channel control for them. However, it can also transport simple signaling for analog terminals, as long as these are limited to the transmission of alphanumeric characters {0, 1, 2 ... E, F} (telephonic digits). The ITU has now fully adopted the protocol. The IETF has stopped supporting the protocol (see RFC 5125 ).

Megaco is essentially based on the principle that the entire intelligence for connection control is concentrated in the Media Gateway Controller (MGC). The media gateway itself does not keep any information about the current status of the connection setup; it primarily provides the ability to connect different types of media streams and to transmit the signaling associated with these streams.

Megaco sees the media gateway as a collection of terminations, each of which represents a particular type of media stream. Scheduling means here a physical operation unit, such as an analog telephone line or a B-channel of the ISDN . However, it can also be a logical functional unit, such as a VoIP packet stream. Such logical functional units are software-based and can be created and deleted in the media gateway using the Megaco protocol.

Megaco / H.248 enable media gateway controllers to control the media gateways. The Megaco / H.248 corresponds to the functions of the Media Gateway Control Protocol (MGCP) and provides the necessary control functions for the IP telephones that work in master / slave mode. In addition, the protocol has peer-to-peer interoperability. It breaks down the H.323 function into subcomponents and specifies the protocols of each component used for the respective communication processes.

The MGCP is an earlier IETF predecessor specification and, compared to the later Megaco, had significant restrictions in scheduling control and its grouping in contexts for a single call.

literature

  • Matthew Stafford: Signaling and Switching for Packet Telephony. Artech House Inc, London 2004, ISBN 1-58053-736-7 .
  • Ted Wallingford: Switching to VoIP. O'Reilly Media Inc, Gravenstein 2005, ISBN 978-0-596-00868-0 .
  • Nicholas Wittenberg: Understanding Voice Over IP Technology. Cencage Learning Customer & Sales Support, Delmar 2009, ISBN 978-1-4354-2727-3 .
  • Wolfgang Kellerer: Server architecture for network-independent service enhancement in heterogeneous communication networks. Herbert Utz Verlag, Munich 2002, ISBN 3-8316-0123-2 .

Web links