Research And Implementation Of Softphone Terminal Based On SIP

With the development of technology in the network and multimedia area, the business of multimedia communication, especially the VoIP technology, which can make a real-time communication connection through IP network, has become a leading element in the Internet applications. VoIP phone can advance the using rate of line, cut cost and realize many value-added services. Even though the quality of VoIP is still need to be improved, we can also believe that with the fast development of technology, VoIP technology will have a prospective future.The most widely used protocols are H.323 and SIP. H.323 is the mainstream in the VoIP equipments and has been accepted in the Chinese communication market. But the SIP is very concise in the structure, easy to be extended and realized, especially more suitable to access the Internet. All these advantages show that SIP is fit for VoIP and the future development of network. So, study the design and realization of VoIP network terminal based on SIP will be meaningful. The network architecture and signaling flow of SIP are firstly explained in this paper, based on the analysis of VoIP service's usage and future, VoIP key technologies and main signaling protocols. Subsequently, the realization thought and framework of the application layers is described in detail, and this part includes user agent and media session module, in the user agent module, a kind of UA structure based on the transaction state machine is designed to solve the complexity problem on the signaling control, in the part of media session, the interface and work flow about voice processing is mainly introduced.Through tests, the terminal can make a good control for SIP signal and also has a high compatibility.