Design And Implementation Of Sip Multimedia Conferencing System, Media Server Control Framework

Multimedia conference has played an important role on the exchange of information, it can provide much more direct and comprehensive communication to users than other applications. Anyhow, multimedia conferences in the past are mostly developed in a integrated way. It is to say that the conference control subsystem and the media subsystem are in one host. This brings a limitation on conference`s media processing capacity. If we separate the two subsystem into different hosts and use SIP to manage the media server, some benefits like improvement of the capability of media process and reduction of the burden of conference control subsystem will occure. What is more, in this way, we give conferencing systems with the scalability: more media type support, more media servers. Right now, IETF is establishing relevant protocols, but most are drafts. So it has some theoretical and practical significance to work on the architectural framework for Media Server Control.The purpose of this thesis is to realise media server control framework using SIP. The realized frameworked can then be integrated into conference system with other modules. To achieve this, this thesis first analyzes the SIP protocol, summarizes and describes the characteristics of SIP protocol and finds that SIP is ideal for multimedia session management. Next we introduce a framework for SIP conference system and mainly illustrate the centralized conference system. It showed that the conference control subsystem and the media subsystem are in one host .so the framework is not suituable for conferences with distributed media servers .that is why the media server control framework is proposed. Left of the paper studys the basic principles, composition and structures of the control frameword. Some key technologies are also studied.then in a company's pre-research demand, we make some change to the framework, so it can be implementation with conference control subsystem or be achieved seperatly.the thesis also solves the problem that how to find media servers`change on status. this is not mentioned in the draft. We make full use of SUBSCRIPT method of sip to let the sipserver inform us once the media server`s status changed. thus the framework has no burden of endless query. It is also do not need to define new messages for query. The whole system will be more simplex. in response to actual demand, we define a new message exchange information between conference control subsystem and media control framework. We also extend the control package to instead the process of establish media stream using 3pcc. In addition, two vague parts of the drafte are discussed: 1. when connecting to the media server ,it is a long connection or connection when needed. It is a multi-connection or single connection. 2. Keep-alive strategy: timely keep alive or only keep alive when needed. At last the thesis tests the major function, and the result showed that the framework can meet the requirements of the conference system.