PURPOSE:
The chapter compares and contrasts the bus, ring and star network topologies. It describes packet routing across local and wide area networks. The methods of data passing are described. Nework hardware devices are described and the OSI Network model is covered.
Megaco/H.248: Media Gateway Control Protocol
Megaco/H.248, the
Media Gateway Control Protocol is used for the control of elements in a
physically decomposed multimedia gateway.
This protocol
describes the relationship between the Media Gateway (MG) and the Media Gateway
Controller (MGC and also known as the call agent). The Media Gateway converts
circuit-switched voice to packet-based traffic.
Terminations and
contexts are the two vital components of the protocol. Streams of data entering or leaving the Media
Gateway are terminations while contexts are when two or more termination
streams are mixed and combined together.
Under command from the MGC, the MG creates and releases the
contexts. More than one stream can
appear in a termination and contexts can be considered to be multistreamed
contexts. Audio, video and data streams
may exist in a context made up of multiple terminations.
Messages are sent in
the ASN.1 format. These are text
messages. These are the commands used in
the protocol: Add, Modify, Subtract,
Move, AuditValue, AuditCapabilities, Notify and ServiceChange.
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