A Study Of QoS Problems In P2P Live Streaming Systems

P2P streaming technology has been widely used and become the important research topic in recent years because of its low cost, good scalability and easiness to implement and deploy. However, there are many challenges in this research field:P2P networks are dynamic self-organized networks and peers will join and leave the system at random. There are differences in the processing capacity, storage and bandwidth capacity of peers. Besides, P2P streaming systems have their own features, such as huge amount of data, strict bandwidth requirement and lag requirements.In P2P live streaming systems, the QoS of the systems is decided by the peers in the whole overlay network and the peers are heterogeneous and unstable. So it's very challenging to guarantee the QoS of the systems and it became an important issue in P2P live streaming systems. The poignant problems are as follows:the playback continuity is unsatisfactory, especially when the peer number is very small or very large; The channel switching is time consuming, usually takes more than 15 seconds; Compared to TV, the playback lag is too long. These problems affect the user experience badly.This paper focuses on the QoS problems in P2P live streaming systems, aiming at improving the playback continuity, reduce the playback lag and enhance the user experience. We fill the bill with the important factors such as uplink bandwidth utilization ratio, overlay construction and playback lag setting. The major measures are as follows:first, we construct a more "flatten" overlay to accelerate the chunk dissemination. Second, the locality-aware technologies are adopted and the AS is the clustering unit. Third, based on the tiered topology, incentives are considered and the peers who contribute more can enjoy short playback lag. Fourth, it adopts synchronous playback setting within a cluster to accelerate the chunk diffusion and asynchronous playback setting among different clusters to facilitate the chunk swarming and reduce the playback lag.We conducted abundant simulative experiments based on the theories we proposed, and through a careful analysis of the experimental results, we testify the fundamental feasibility and effectiveness of these optimal strategies.