Research Of P2P Media Service System

It was reported by China Internet Network Information Center(CNNIC) that the number of network users and broadband users in China ranks No.1 in the world up to June 2009 and there are more than 200 million network video users. The fast increasing of broadband network users is a great impetus to the broadband network services. As one of the most important network services, the video service creates many new business opportunities, provides a great perspective for the video service system and its key technologies and is a fast growing spot of the information industry. The media data storage, distribution and sharing technology is critical for a video service system. The sharing-based P2P (peer-to-peer) technology is a very good candidate to realize the media data storage, distribution and sharing, and has caught much attention recently.There are 3 typical architectures of P2P technology. The first one is the centralized directory architecture, which is vulnerable to single node failure, suffers from the poor reliability and security, and cannot be implemented in the large scale networks. The second one is the pure P2P network architecture, which occupies much network bandwidth, may easily result in network congestions and even network break-down, and cannot provide any performance guarantee. The third one is the hybrid P2P network architecture, which strongly depends on the super nodes and whose fault tolerability could be weak.The present thesis proposes a new multi-level P2P architecture for video service systems. The superiority of the multi-level P2P architecture is confirmed by the experiments on a testbed. Under the new multi-level P2P architecture, there are 5 types of nodes, including central media servers (CMS), directory servers (DS), media distribution centers (MDC), edge media nodes (EMS) and home media terminals (HMT)。These 5 types of nodes compose a dual-layer P2P network, which comprise a wide area P2P media content storage and distribution network and a local area P2P media content storage, distribution and service network. In the first level (wide area) P2P network, the distributed nodes are organized according to the structure of the Kautz graph. In the second level (local area) network, the dual characters of the edge media nodes and the special service capability of the home media terminal nodes are integrated to improve the overall system's service performance and provides QoS guarantee. The excellence of the multi-level P2P architecture is shown by both the theoretical analysis and the experiments.In the multi-level P2P media data distribution service networks, deploying and caching the media data can improve the efficiency of the data sharing and the overall system performance. The available data deploying and caching strategies are often designed for certain environments and have limited usage. We have not seen any efficient strategy for P2P networks. The present thesis proposes a new media data deploying and caching method for multi-level P2P networks, which is built upon the data request property of media data in networks. The new method derives the life period and status of media data based on the statistical behavior of distributed nodes, gives the expectation of the cached data and the positioning node, realizes the final data deployment and caching, achieves the more efficient data distribution in the overall network, provides the more effective data sharing service and significantly improves the systems performance. It has been shown by the experiments in a testbed that the new media data deploying and caching method can greatly improve the system's QoS in the multi-level P2P data distribution and service networks. Moreover, the present thesis proposes a new media data request model for the multi-level P2P networks and defines the critical parameters and functions of the concerned model. The given model can serve as an important reference for the data deployment and caching.Based on the achieved results, the present thesis builds a typical P2P media data service prototype system, "A Video-On-Demand System based on the Multi-Level P2P Architecture", designs and realizes all distributed nodes and the major business processes. Furthermore,200 nodes are deployed in the CNGI (Chinese Next Generation Internet) demon network to construct a verifying system under the proposed multi-level P2P architecture. The verifying system has passed the test run. The results of the verifying system confirm the effectiveness and efficiency of the .achieved results.