On Server-Aassisted Peer-to-Peer Video-on-Demand System

In recent years, Peer-to-Peer (P2P) video-on-demand (VoD) application has become common in the world of the Internet. P2P VoD mechanism is good at the scalability and cost of deployment, but peer churn and heterogeneity in nature impose significant impact on the system performance. By introducing Client/Server (C/S) mode into a pure P2P VoD system, it is possible to achieve the merits of both modes, i.e., high scalability and guaranteed service, and further to provide good quality of service at reasonable cost.This thesis proposes a server-assisted P2P VoD system (SAVoD). The proposal consists of system architecture, server-assisted transfer mechanism, P2P transfer strategies, common work flows and protocol specification. Server assistance mechanism is designed with the concerns of both peer playback deadline and server load, and consists of two parts available for startup and playback periods, which help to reduce launch delay and to improve playback continuity respectively.The simulators of SAVoD and BiToS, a common type of P2P VoD system, are developed based on NS2 and its extension, PDNS. The codes simulate the interactions of protocol messages and data transfers among the nodes in a system, and provide NS2 standard interfaces for pro-simulation configuration as well as system-specific traces for post-simulation analysis.Based on the developed simulators of SAVoD and BiToS, a lot of simulations are performed with typical ISP network topology and VoD user behavior. Statistical analysis of simulation traces shows that: (1) SAVoD offers shorter startup delay and higher playback continuity with lower server load than BiToS; (2) while the bandwidth of servers is increasing, the improvement in terms of startup delay and playback continuity is getting limited.The results presented in this thesis can be further applied to the development, analysis and deployment of server-assisted P2P VoD system.