Design And Implementation Of A VOD Streaming System With CDN-P2P Hybrid Architecture

In recent years, the main way for carrying information on Internet has changed from traditional characters to multimedia data including images, audio and video. As a kind of applications for providing video/audio services, the VOD streaming system has advantages such as short waiting latency, small buffer cost, and good playing quality. It's used to provide movie programs, remote lessons and video games. With the rapid development of computer hardware and broadband communication technology, VOD streaming system, which covers wide area and provide services for vast users, will have a good prospect of application.In current VOD system design technologies, traditional C/S architecture has too poor scalability to provide service for vast users; IP multicast lacks support on network layer, so it cannot be applied on current Internet. For now, there are two main ways to implement VOD system that supports vast users, Content Distribution Network (CDN) or Peer-to-Peer (P2P). CDN supports vast distributed users well, and can provide good Quality of Service (QoS), but it requires mass servers, so the cost is high. On the other hand, P2P has good scalability and fluency as well as low cost, but providing VOD services with pure P2P technology cannot guarantee QoS for end users.To solve the above problems, this thesis proposes a design of VOD streaming system with CDN-P2P hybrid architecture which combines the advantages of both CDN and P2P technologies. The proposed system has good scalability, adaptability and robustness, so it can provide QoS for distributed vast users, and also saves server costs. The main contributions of this thesis are as follows: (1) In the design of CDN layer, we group the regional servers based on the idea of clusters. Each server group contains a Region Manager (RM) and several region servers (RS), RM deals with user request and global information gathering, and RS provides content services for users, so as to balance the load and guarantee fluency. (2) Because of the hybrid architecture, the proposed system can avoid mismatch between P2P application layer and network layer which is a big problem in traditional P2P systems. In the design of user P2P network, the user nodes who are watching the same segment are formed as neighbors, and a combination of local rarest strategy and random strategy is used to download data to improve the throughput of the system. (3) We propose a partitioned buffer scheduling strategy at user P2P layer, except buffers the latest program data played by the node, the strategy also uses free bandwidth of some users to download segments that are most required currently, so as to optimize the distribution of program data and improve system performance. Simulation results show that the proposed strategy outperforms the common strategy which only buffers the latest data and has good scalability.