SIP

Firstly, SIP is used as the short of Session Initiation Protocol which is the application-layer control protocol used as the signaling protocol for Internet Telephony.

It can also establish sessions for features like audio/video conferencing, call forwarding over the IP network. So it enables the service providers to integrate the basic IP Telephony services with Web, E-mail and chat services etc.

Other than the user authentication, redirect and registration service, SIP Server while based on the geographical location of the person being called, SIP also support usual telephony functions like personal mobility, time of day routing and call forwarding.