The Design And Research Of SIP Based Multimedia Distance Education System

Distance Education is fully new style education. Compared with traditional education, it breaks away from the limitation of time and space, optimizes the configuration of education resource and makes education more efficient. With the rapid development of Multimedia Technology, Distance Education will evolve to Distance Multimedia Education gradually.In fact, Distance Multimedia Education is the application of Multimedia Communication in educational environment. In recent years, Multimedia Communication evolves to Multimedia Network Communication in IP network. So, the trend of Distance Education is Distance Multimedia Education in IP network.There are two popular kinds of application-layer signaling protocol at the present time in IP Based Multimedia Network Communication: H.323 and SIP (Session Initialization Protocol). H.323 is brought forward by ITU(International Communications Union), it takes H.255.0 as call control protocol and H.245 as media control protocol. The Process of establishment of call and media logical channel are separate. The exchange of a large number of signaling messages is required before RTP session is established. So, it takes long time to establish the session. SIP is brought forward by IETF(Internet Engineering Task Force), it uses SDP(Session Description Protocol) to describe session and media. The call control messages and media control messages are transmitted simultaneously. So, it takes short time to establish the session. Otherwise, SIP has additional advantages over H.323 such as SIP messages are simple and readable, SIP is well extensible and so on.SIP is text-based, C/S (Client/Server) pattern protocol. SIP Register Server, SIP Redirect Server and SIP Proxy Server are defined to contribute to the establishment of SIP Session. Similar to H.323, SIP also uses RTP(Real-time Transport Protocol) to transmit media data.There are three kinds of system architecture for SIP-based multimedia conference system: loosely coupled architecture, fully distributed architecture and tightly coupled architecture. Among them, tightly coupled architecture is most widely used. There are several kinds of logical entity defined in tightly coupled conference system: FOCUS, Mixer, Conference Policy Server and Conference Event Notification Server. As far as physical realization is concerned, centralized server mode, application and media server mode, distributed media processing mode are the three primary kinds of physical realization mode.According to the model of tightly coupled SIP conference system, with modification and supplement, this paper brings forward a detailed scheme of SIP based Video Class System using SIP stack technology. Otherwise, Considering popular Web technology at the present time, this paper also brings forward a design scheme of Web-based, Browser/Server Pattern Education Management System.