The Design And Implementation Of IP Voice Soft-Terminal Based On SIP

With the development of technology in the network and multimedia area, the business of multimedia communication, especially the Voice IP technology has become a leading element in the Internet applications. One of the key technologies for the development of Voice IP is Signaling. And at present, the most widely used protocols are H.323 and SIP (Session Initiation Protocol). SIP is very concise in the structure, easy to be extended and realized, especially more suitable to access the Internet. The research of IP Voice Soft-terminal based on SIP will be of meaningful practical use.This paper is based on the the project"The design and Implementation network communication system based on SIP". It firstly anlyzes the key technologies for IP voice soft-terminal development and the network architecture of SIP, with the emphasis on comparison between SIP and the H.323 standard..It then analyzes the requirements of soft-terminal according to the research above. Based on the requirement results, this paper brings out the design principle by using the reference of layer design and module design, and this soft-terminal is divided into three layers: application layer, user agent layer and stack layer. This paper emphasizes the stack layer of soft-terminal, including Transfer module, Parser module and Transaction module. And then, it introduces the implementation of IP voice soft-terminal based on the Windows platform, including the user agent, the capture and compression of audio steams, the working thread of IP voice soft-terminal, and so on. At last, it shows that this soft-terminal can create the connection by SIP Signaling and finish the real-time communication through IP network by a functional testing experiment in local area network. All of the results indicate that both the research results and design plan, and also the implementation are reansonable and feasible.The soft-terminal designed in this paper implemented the basic speech functions. In the research of the next stage, other functional requirements, such as video-phone and voice-mail, will be expanded based on the terminal. And with the expanding, the advantages of SIP, such as concision and expansibility,will show themselves.