隨著寬頻網路的發展，使用者對於線上會議的需求也漸漸的浮現了，換句話說使用者希望能夠在網路中享受到線上會議提供的互動服務，為了要在現實的網路之中提供這種服務，大部分的系統會使用Client/Server (C/S)的架構實作，它可以提供比較高品質的服務給使用者，其中包括他能提供低延遲以及較低的封包遺失率，但是使用C/S的架構卻也有其缺點，大量的使用者會消耗大量的頻寬這對Server會造成很大的負擔，換句話說我們必須使用更多的Server資源去提供服務給所有的使用者，為了要解決這個問題有些系統會用P2P的架構來實作，用這種架構可以減少Server的負擔。雖然用P2P的架構可以大大的減輕Server的負擔，但是如果將它用在線上會議的應用上面，它仍然有缺點，也就是P2P的架構很難提供很高品質的服務，這是因為P2P架構中部份Server的功能會由使用者擔任，而這些使用者往往是不穩定或是不受控制的。
在這篇論文中，我們提出了一個嶄新的P2P遞送系統，這個系統可以同時減少Server的負擔以及保證每個使用者高品質的服務，而系統所使用的演算法，可以在mesh的拓樸中偵測出有哪些使用者的服務品質降低，並且幫助他們能夠迅速地恢復。
最後，我們實作出了這個系統，並且在現實的網路中和台灣學術網路(TANet)底下對進行測試，結果顯示我們的系統可以有很好的效能，而這些數據在未來相關的研究上面也可以提供不少的幫助。

With the development of the broadband network, the need of video conference has emerged, where users need the program to provide interactive services in the network. In order to provide this kind of service, many systems will be implemented by the Client/Server (C/S) architecture, which can provide high quality services including low latency and low loss rate to clients. However, a great amount of peer’s bandwidth consumption will largely increase the server’s loading, where we need to spend more resources to support users. In order to resolve this issue, some systems will use the P2P architecture to reduce the server’s loading. The P2P architecture can largely decrease the server’s output bandwidth, but it still has some disadvantages in the video conference for the difficulty to provide high quality services to users. The reason is that a part of server’s functionality is supported by peers, which is unstable and unrestrained.
In this thesis, we try to propose a novel P2P system, which can deliver the media streaming data. The system can reduce the server’s loading and guarantee the user’s service quality at the same time. By the proposed algorithms, a user can easily detect the decrease of the video quality in the mesh-based topology and quickly recover from the poor situation.
At last, we implement and test the system in the real network and Taiwan Academic Network (TANet), where the experimental result shows a superior performance of our system. The result can also be used as a reference to relative studies.

Chapter 1 Introduction 1
Chapter 2 Related Works 5
Chapter 3 System Architecture 10
3.1 System Architecture Overview 13
3.2 P2P System Architecture 15
3.2.1 P2P Media Server 15
3.2.2 SYN Server 19
3.2.3 Log Server 22
3.2.4 P2P Manager Server 23
3.3 Implementation 26
3.3.1 System Structure 26
Chapter 4 Algorithms 31
4.1 Rescue Algorithm 32
4.1.1 Choosing Algorithm (Rescue) 33
4.2 Merge Algorithm 39
4.3 Join Algorithm 41
4.4 Leave Algorithm 43
Chapter 5 Performance Evaluation 45
5.1 Experiment Setting 45
5.2 Experimental Result 47
Chapter 6 Conclusion and Future work 57
References 58

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