隨著科技的進步，愈來愈多不同類型的網路應用程式接連著被提出來以滿足使用者的需求，線上會議系統即為其中之一，他提供了一個網路空間讓使用者可以在上面互動，會議的參與者可以在裡面分享視訊，而會議旁觀者可以透過此系統觀看整個會議的過程，然而，當觀看者人數越多，表示伺服器需要更多的上船頻寬來支援會議中影像的傳送，這對於伺服器來說，是一個很大的負擔。
在這篇論文中，我們提出並且實作了一個機於點對點傳送的廣播系統，負責轉播線上會議系統的串流給觀看者，透過點對點的傳輸，可以有效的節省頻寬消耗，降低伺服器的附載，並且節省系統在大規模影音轉播時可以節省開銷。透過本系統，可以將會議室裏面的串流送至所有的觀看者端，觀看者可以透過網頁來收看這些串流。除此之外，本系統也提供了一個救援機制，負責處理當網路壅塞而造成上游傳輸能力不足，使得節點無法順利撥放的狀況，有了救援機制，本系統可以有更好的服務品質。
之後，我們也設計了一些情境來測試我們的系統，在實驗中，我們模擬會觸發救援機制的網路狀況，實驗的結果將被記錄與分析，最後我們根據這些結果提出一些建議來改善本系統。

With the advancement in technology, more and more network applications have been implemented to satisfy users’ requirements. The online meeting system is one of these applications. It provides a network platform for attendee to interact with each other and viewers can watch the meeting as well. However, when the number of viewers gets larger, the server needs more output bandwidth to support the stream transferring. Thus, sharing video in online meeting system can be a huge burden to the server.
In this thesis, we propose a P2P-based live broadcasting system for the online meeting system. By using the P2P technology in live broadcasting, we can reduce the bandwidth consumption, decrease the server’s loading and make large scale video broadcasting service an inexpensive application. With this system, video streams in the meeting room are transferred together to each viewer. Users can watch these video streams on the web page. The system also provides the rescue mechanism to handle the case that peers get insufficient input stream due to the network congestion. With this method, we can ensure that the system can have higher performance.
Besides, we implement this system and design some experiments to test the performance of system. During experiments, we simulate the environments that will cause the rescue method to happen. The experiment results are recorded and analyzed for further suggestions for the service.

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