Telephony application server

The Application Server The application server provides call-termination or subscriber-independent applications. These include such capabilities as local number portability, free-call routing resolution, conference bridge services, and unified messaging. The PSTN versions of these applications are frequently known as 800 numbers in North America. The subscriber has to explicitly place a call to the application server.

Application server applications are of two general types, those that are signaling only, and those that involve media manipulation. The former are often related to routing resolution -- local number portability, free-call routing, and other services where the dialed number must be translated to a routable address. An example involving media manipulation would be conference bridge applications, something with which most business people are very familiar. The call steps include:

Each user calls in on a pre-published number. The dialed number is translated into an IP address and named the endpoint of the application server, and the call is routed there. The application server connects to the media server, instructing it to play a greeting and collect the conference number. The media server returns and conference number, and the application server instructs the media server to play a prompt to collect the authorization number. If the digits collected are correct, the application server tells the media server to move this call to a particular conference bridge.