Design And Implementation Of Conference Control Function In A SIP-based Video Conference Server

H.323 and SIP are the main signaling protocols which control multi-media sessions in a multimedia conference system over the packet network .H.323 is maturer than SIP in application,but SIP is rather simple,flxeible,opening and extendable thanH.323 which is complicated in implementation and extending and costs much.As soon as SIP is released,it is cared and supported. There is no an applied SIP-based video conference control system,it is valuable and necessary to study it.Just surrounding using SIP how to design an IP-based video conference system and how to control and manage the conference,we develop the research and discussion about the system architecture and key control mechanismes.As a mechanism to coordinate and to manage multiple users using different media in different conferences, video conference control is the key part of video conference server,it is the basis and core in conference sever. After studying and researching present SIP conference model and SIP control theory, we put forward a new SIP conference control model. This model includes SIP session control, expanded protocol control, policy control and conference notification service. In this thesis, we design and implement the four parts in detail. In terms of SIP session control, we implement many functions, such as creating conference, joining conference, leaving conference, querying conference and so on; in terms of expanded protocol control, we design and implement conference control message, floor control message and information release message; in terms of policy control, we show the function module structure, apply the binary floor control protocol to conference policy control and describe the implement of floor control mechanism; in terms of conference notification service, we give the structure of conference notification service, design and implement conference notification mechanism.The realization is completely compatible with the latest version of SIP:RFC3261.On the foundation of the asterisk project which is open source under Linux OS, we successfully implemented SIP-based video conference control prototype system. It is worth of developing applied system and helpful to study SIP-based video conference system and multimedia applications. It make greate contribution to the development of SIP video application server.