軟體定義網路的發展，已成為研究者們實現自己的想法來解決網路問題、增加網路效能的重要方法。在現今便利的網路環境中，我們生活常常會利用現場直播、視頻點播等影片檔案來觀賞影片或獲得資訊，如果有很多不同的使用者需求相同的影片檔案，我們可以利用多播(multicast)的方法來傳送並節省頻寬。因此本論文採用軟體定義網路集中式的架構並設計有效率的多播演算法。在本論文提出的方法中，我們有三種不同的方法，在第一個方法中，我們會考慮平衡連接成本和網路頻寬使用率中，找到最好的多播路徑。在第二個和第三個方法中，我們會在資料來源和使用者間，選用有最大剩餘頻寬的路徑作為我們的多播路徑。實驗證明，相對於傳統的有線網路傳輸協定，本論文的方法可大幅提昇網路的利用率和使用者需求成功的比率。

Software Defined Networking (SDN) is a new approach to designing, building and managing computer networks. In recent years, people often use the livestream to get video content through Internet. Multicast is used to transform the same video files to different users. In this thesis, we propose efficient multicast algorithms to solve the multicast problem in SDN environment. In the first algorithm, we choose the multicast path by considering the balance of bandwidth utilization and communication cost between the source and clients. In the second and third algorithms, we choose the multicast path by the path with maximum bottleneck bandwidth between the source and clients. Simulation results show that our algorithms can improve the network bandwidth utilization and successful rate of the multicast requests than the previous works.

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