Abstract: P2P-VoD systems have gained tremendous popularity in recent years. Existing research is mostly based on the traditional theoretical assumptions. However, what is the performance of these assumptions is not known in the real world. It is particularly valuable to understand how the real-world system works. This paper presents a comprehensive measurement and analysis on CoolFish, a real deployed P2P-VoD system, and proposes some statistical models different from the traditional observations on user behavior: the access pattern does not match Poisson distribution; session time does not have positive correlation with movie popularity; jump frequency does not have a negative correlation with movie popularity as assumed in previous studies. This paper analyzes the reasons for these results.

Key words: peer-to-peer (P2P), video-on-demand (VoD), streaming, P2P evaluation model

摘要： 近些年，P2P点播系统（P2P-VoD）受到广泛关注，其大多研究工作基于理论性的传统假设，这些假设在真实的系统中是如何表现的不得而知。因此，在真实P2P-VoD系统中对传统假设进行全面的测量和验证就显得十分迫切。对实际运行的P2P-VoD系统CoolFish进行了大量的测量与分析，发现了一些不同于以往假设的结果：节点加入不是简单地服从泊松分布；观看时间和影片流行度不呈严格的正相关性；跳转频率和影片流行度不呈负相关。最后对这些结果进行了深入的分析和讨论。

关键词: peer-to-peer（P2P）, 视频点播（VoD）, 流媒体, P2P评价模型