IPT Network Components

An IP Telephony (IPT) solution can comprise several components. The central component of the solution, or any IP network for that matter, is a routed backbone. There are many makes and models of routers, with each manufacturer claiming that its approach to router design has some fundamental advantage over its competitors. Typically, routers with very low latencies (e.g., can move packets through the router quickly) are better. The routers in the core of the network may need to support additional capabilities required by the applications in the network. That might entail such things as the integration of routing with lower layer switching, the support of special routing or reservation protocols, or the ability to communicate and use quality of service (QoS) information of various types.
At the edges of the IP network are the devices that connect the packet world to the traditional circuit-based telephony world: the media gateways. The fundamental purpose of the gateway is to digitally encode and packetize the voice signals so they can be sent across an IP network. The gateway can connect traditional analog phones to the IP backbone, can bridge between the IP world and a traditional PBX world, or can connect the entire PSTN to the IP backbone. Gateways can be stand-alone devices, or they can be integrated into routers or PBXs.
The media gateway controller, sometimes referred to as a call manager, voice server, or softswitch, is responsible for finding destination stations on an IP telephony network and dealing with the authentication, authorization, and accounting (AAA) functions. The controller is responsible for establishing calls between calling parties. The media gateway controller can be a standalone device, running on a conventional server, or integrated into a PBX.

Daniel Casique EES seccion 1