Large-scale live peer-to-peer (P2P) streaming applications have been successfully deployed in today's Internet. While they can accommodate hundreds of thousands of users simultaneously with hundreds of channels of programming, there still commonly exist channels and times where and when the streaming quality is unsatisfactory. In this paper, based on more than two terabytes and one year worth of live traces from UUSee, a large-scale commercial P2P live streaming system, we show an in-depth

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... rk-wide diagnosis of streaming inefficiencies, commonly present in typical mesh-based P2P live streaming systems. As the first highlight of our work, we identify an evolutionary pattern of low streaming quality in the system, and the distribution of streaming inefficiencies across various streaming channels and in different geographical regions. We then carry out an extensive investigation to explore the causes to such streaming inefficiencies over different times and across different channels/regions at specific times, by investigating the impact of factors such as the number of peers, peer upload bandwidth, inter-peer bandwidth availability, server bandwidth consumption, and many more. The original discoveries we have brought forward include the two-sided effects of peer population on the streaming quality in a streaming channel, the significant impact of inter-peer bandwidth bottlenecks at peak times, and the inefficient utilization of server capacities across concurrent channels. Based on these insights, we identify problems within the existing P2P live streaming design and discuss a number of suggestions to improve real-world streaming protocols operating at a large scale.