Design And Implementation Of A SIP-Based IP Phone

With the popular applications of Internet, Internet IP Phonehas caught more and more attention with its low cost and low maintaining expenses. Under this scenario, SIP (session initialization protocol SIP) emerges as a new research topic. It serves as a controlling protocol to establish, modify and end multimedia conversations based on the Internet. Furthermore, it has lots of advantages such as flexibility, simple structure, short calling establishment time, easy implementations of added business and distributed control.In this thesis, we study the Internet IP Phonesystems based on SIP protocol. After thorough research on SIP protocol, we introduce the oSIP source codes to implement our system. In addition, we test the system over repro internet server. In this system, users will first register and save their personal information on the server. If a registered user is called by others, the IP address which stores the user's personal information will be extracted. After that, a call will be established and ended according to SIP protocol. After a conversation is successfully established, audio files will be extracted and transmitted over the Internet in the way of RTP. Based on the above procedures, an Internet based IP PhoneSystem is realized and can perform similar functions with phones between any two computers.Some important protocols and concepts used in SIP software phone which include SIP protocol, SDP protocol and RTP protocol are first described in this thesis. After that, system analysis and system design with respect to our IP Phonesystem are given. Details of SIP User Proxy were illustrated. In addition, we create a testing environment in Local Area Network and conduct experiments to test our system. Finally, we give our future work about SIP protocol.