Wednesday, December 2, 2009

Softphone Architecture.

Above diagram shows the basic data and signaling path established during a call between a SIP phone and a 3G phone.

The SIP server is consists of SIP Registrar and the SIP Proxy. The task of the SIP servers is to act on behalf of the two calling parties to facilitate the session establishment. The proxy server receives SIP requests and forwards them on behalf of the requestor. Another task of the proxy server is locating the proxy server of the other calling party by performing a particular type of DNS lookup to find the SIP server which serves that party. In order to do that the proxy server consults a database called location service also. In addition to DNS and location service lookups proxy servers can make flexible routing decisions to decide where to send a request.

Registration is another common operation in SIP and it is a one way that a SIP server can find the current location of the other party. During the initialization and at periodic intervals the SIP softphone send REGISTER messages to the SIP registrar. The registrar writes this location data to the database called location service where it is used by the proxy servers.

The VSDP is the Video Service Delivery Platform and it acts as an interface between the 3G-324M and the IP network. It supports real time bidirectional streaming of video sessions between 3G-324M mobile phones and multiple IP based video applications.

No comments:

Post a Comment