隨著雲端運算的發展，數據中心被廣泛的使用，而在多服務群播的環境之下，若一個客戶端同時對多個伺服器提出請求和要求，傳輸過程中因為TCP其重傳機制與特性容易造成網路傳輸的崩潰，這就是所謂的TCP Incast。 本文主要探討在雲端環境中，多人接收即時影像的效能問題。在傳輸方面使用數據噴泉(Digital Fountain)的概念，以UDP的方式取代TCP傳送，用LT-code確保資料的傳輸性，影像則使用可適性視訊編碼(Scalable Video Coding，SVC)的方式作為編碼，將影像分為基礎層與增強層以提供客戶端不同的服務品質，而在雲端多服務群播的環境下，針對即時影像每張frame具有時效的特性，設計了以數據噴泉為基礎的可適性視訊編碼群播方法，改善網路效能同時提供客戶端更好的服務品質。最後使用階層式網路設計實驗，以便比較方法在遇到不同環境的優劣。 經由實驗結果得知，直接放棄網路狀況不好的客戶端可以有效地提升整體網路效能與服務品質，只有在所有客戶端的能力相同情況下，才可以考慮保證所有客戶基本服務品質。; Date center network (DCN) is widely used with the development of cloud computing technology in recent years. In the multi-service environment, the client calls for service from multiple servers at the same time. Because of the retransmission mechanism of TCP, the transmission of network may be easily collapsed, which is called TCP incast. In this thesis, the performance of real-time video among multiple receivers is studied based on the cloud computing environment. In the aspect of transmission, the concept of digital fountain is adopted, and UDP is used instead of TCP as the transport protocol. And LT-Code is applied to achieve reliable data transmission. In addition, employing scalable video coding (SVC), video is divided into the base layer and the enhancement layer to provide different kinds of quality of service (QoS). Aiming at the real time characteristic of each frame in video, we propose a multicast SVC method based on the digital fountain in cloud. The proposed method could improve the network performance and provide better QoS for clients. Finally, we design and implement an experiment using hierarchical network in order to compare the different performances in different environments by using the method. From the experimental results in this thesis, it shows that the system network performance and cilents’ QoS can be improved efficiently when giving up the clients with poor network condition if receivers have different link capacities. On the other hand, when receivers have the same link capacity, all the clients’ basic QoS could be guaranteed.
