| With the explosive development of the Internet and users, people become more and more reliable on multimedia applications to get information. The multimedia streaming system has been projected as"killer-app"for the Internet now, and people can access the media content from the Internet anytime and anywhere. Streaming the media content to a large number (usually millions) of people stably and continuously has become a hot research topic no matter in academia or in industry. There are two alternative technologic ways for delivering media content to endusers: one way is CDN (Content Delivery/Distribute Network), and the other way is P2P (Peer to Peer) networks, and each has its inherent advantage and disadvantage. CDN deploys many edge servers around the country or the world, and it enables the media content provider to deal with much larger user requests, the end users to get the content through the shortest packet delivery paths from appropriate edge servers, and the ISPs to avoid congestion in backbone. Since there are many edge server in CDN, the operation cost is also very high; and because of its traditional client-server approaches, it cannot efficiently solve the problem of scalability and address the flash crowd phenomena, especially in live streaming systems. In P2P networks, media content are shared among users, so it can achieve high scalability while keep the server load in minimum. Because of the users entering or leaving unexpectedly, it has serious impact on Quality-of-Service of the network. The decentralized and uncoordinated architecture may also results in variable stream quality and unfairness, such as end users behind a NAT may not contribute any capacity to the network.We design and implement a CDN-P2P hybrid Video-on-Demand system which incorporates the best of both technologies and at the same time offset each other's deficiencies. In our system, the source server distributes media content to the CDN edge servers, and CDN edge servers also can share their media content in P2P way. When a user wants to get the media content, it is redirected to an appropriate edge server, and the P2P overlay is localized on a per-edge servers. First, it can minimize the changes in the existing CDN infrastructure; Second, it can effective restrict the P2P traffic to a local domain, so it is ISP friendly; third, it can preserve the reliability and manageability of CDN system. We classify the VoD system into three categories: traditional C/S VoD system such as PPLive, user generated content VoD (UGC-VoD) system such as YouTube and Live-VoD system. We analyze the character of each system, like video generated ways, video length, and video popularity. We also make a comparative analysis of user behavior in each VoD system, such as user access time distribution, user viewing duration, user interactive operations, and etc. A more efficient VoD system could be build in the future if this analysis be taken accounted more carefully.At last, we also talked about other factors that influence the efficiency of media system, such as the cache method, P2P route strategy, and the transport protocols. High efficient media system should be a set of optimal strategies chosen. |
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