Abstract:

Different P2P live streaming systems represent different design conceptions and present obviously different characteristics. Currently, most studies on P2P living streaming systems are based on PPLive, while PPStream is hardly known to researchers because its protocols are not open to public. The contributions of this paper are: (1) peers’ buffer structure and sharing mechanism in PPStream live system are figured out in this paper. It is found that peers have jumping sharing window in PPStream which is different from PPLive with sliding sharing window. In PPStream, video chunks are classified into different windows (or phases). Peers downloading chunks in the same phase can share data with each other; (2) authors use a window jumping model to analyze the impact of buffer structure and sharing mechanism on the reciprocal relation between peers. It is found that the sharing mechanism in PPStream can result in peers’ phase fluctuation; (3) based on the features of phase fluctuation, authors develop a predicting model to describe the user population of different phases. Numerical evaluation and system simulation both show that the model can well reflect the fact that the contention on bandwidth resources contributes to the peers’ phase fluctuation. It can bring insights to the work of further improving the bandwidth assignment strategy and peers’ playback quality.