Design And Implementation Of A Sip-based Video Conferencing Control Server

Video conferencing systems to meet the needs of people remote interactive communication, is increasingly favored by people, and have a wide range of uses in business, education, military and other fields. However, different audio and video terminals can not call each other and establish the media session, so the IETF developed SIP standards to address the different audio and video interoperability problems between endpoints.Based on the research on SIP protocol, and according to the requirements of video conferencing systems, this paper designed and implemented of a video conference control server to control each SIP terminal. SIP is already a mature point to point call protocol in the IP network; however, standard for conference calling is still constantly improving. Therefore, the control server of this article made reference to the RFC4353 SIP-based model to implement a centralized conference, and expanded the definition of a series of XML-based SIP message format of session control signaling to achieve the functions of the video conferencing system.The core component of the centralized conferencing model is the central control node called Focus. Focus establishes SIP dialogs with other SIP terminal, in order to provide transport channel for the conference control signaling. Focus is a SIP user agent, so this paper implemented the user agent meet to the needs of video conference system, based on the definition of the SIP standard RFC3261 and JAIN-SIP stack. Besides maintaining the SIP dialogs between SIP terminals, control server needs to execute the conference business logic (such as the conferencing strategy and media management), as well as interactions between other components in the video conferencing system. Therefore, based on J2EE platform, control server encapsulated the conference business logic, and cooperated with conference management server and QoS server in conferencing. In addition, the video conference system can not only run in IPv4 network, but also IPv6 network.This paper describes the design ideas of video conferencing system control server, and the details in implementation. The results of system testing verify that the video conferencing system can satisfy the demand for interactive communication between people; and the system can be built into a flexible, easy to extend software system, depending on the SIP standard.