Research And Implementation Of IP Phone Based On SIP

With the extensive application of Internet, IP Phone impacts the conventional telephone service because of the low cost and the prospect of market. Much government take an active attitude of IP Phone, and many telecommunications take part in researching IP Phone. Ministry of Information Industry attaches importance to the technology of IP Phone in China.Now, H.323 has widely applied in the IP Phone in China. At the same time the merits about Session Initiation Protocol should be seen in the simpliness, the distributing controlling and so on. And Session Initiation Protocol can quickly develop with the technology of soft switch, the performance of Internet. But the technology of Session Initiation Protocol is immature, and intercommunication of different terminal is poor, so there is a necessary to research the terminal software by Session Initiation Protocol.This article is the research on the above problems. Main research is as the following:First, this article discusses the correlative protocol such as Session Initiation Protocol, Session Description Protocol and Real-Time Transport Protocol, analyses the format of the message, the field for the message and the meanings of all the fields, demonstrates the hardware.Second, according to the function of the terminal, the article analyses the functional module including the user agent, real-time transport and the management of the system's resource. The module of user agent need accomplish these tasks of making the message, analyzing the information, user agent, negotiating about the media. The module of real-time transport need complete these tasks of converting the data, coding and decoding the data and receiving and sending the packet. The module of management of the system's source need manage the keyboard and display and so on. Finally the software of all the modules was give.Experiment in PC demonstrates this designed software can accomplish the basic function of IP Phone such as creating the connection by Session Initiation Protocol, negotiating the media by Session Description Protocol, transporting the stream of data by RTP/UDP/IP.