The controller is a more central function. The media gateway controller can sit within
the core network, or it can be placed within a specific geographical location and provide
call control for many different media gateways. The media gateway controller function
(MGCF) is the brains of the VoIP network. The MGCF is also where the signaling
portion of the switch is placed. It is the MGCF that communicates with other MGCFs
within its own network, providing call control between there various entities.
Since the processing for a call is not distributed in key areas, this function can be
used to support multiple communities of interest, rather than deploying one per town
that can only be used to support that one town. This is the direction of VoIP deployments
and the major attraction from an operator??™s perspective. It does not come without
issues, however.
The multitude of signaling protocols is one of the largest issues and has caused
implementation nightmares for many operators. This was especially true for wireless
operators trying to support applications. Since wireless is heavily dependent on databases
(the Visited Location Register and the Home Location Register, for example), it
becomes paramount that every entity within the network be able to communicate with
the Mobile Switching Center (MSC) to access these resources.
The applications and features in the VoIP model are also separated from the switching
function and deployed on application servers.
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