| Modern distance education system is a system, which combines the knowledge of digital technology, network communications technology, multimedia technology and computer technology. In order to solve some problems existing in Distance Education of Network at present, this thesis studies and discusses optimizations and designs of the non-realtime education system which is realized based on web. At first, the overview of development and situation of distance education are firstly demonstrated. Then characteristics of distance education and functions of the non-realtime education system are described. And next,, Queuing theory —the theoretical foundation of this thesis and mathematic theories are introduced in brief. In the part of the optimization of network structure, the thesis has made a detail analysis on the queuing models used in system design and performance of a CODs, the quantitative relationship among the following factors is emphatically studied: traffic ρ, users average arrive λ, system channel capability n, system latency probability, blocking probability, mean queue length, system throughput and so on. Another mainly discusses in this paper is the optimization of network performance. We put forward a dynamic routing method based on QoS for multimedia, which dynamic chooses route for multimedia data according to not only different requirements but also the existence resource status of the net, implement different QoS services in network layer through routing mechanism. Lastly, thesis focuses on the designs and realization of a non-realtime education system. All in all, a distance non-realtime education system with centralized management and distributed Courseware-On-Demand servers is introduced in this thesis. We do the work from theoretical analysis of model to the design and realization of real system. This system improves the utilization ratio of resources, decreases the waiting time of clients, enhances throughput of the system. |
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