Data Availability in P2P Streaming Systems

Nowadays, sharing multimedia contents in P2P systems has become a common practice. In general, it is done in "download" mode as any other type of data. However, due to their huge volume and real time constraint, multimedia data present another consumption mode which is the streaming mode. In this mode, rather than downloading the entire data before viewing it, it initiates a stream from the source peer to the destination one. The advantages of this mode are numerous such as latency reduction, copyright preservation (in the sense that the consumption peer does not hold the multimedia content), etc. Nevertheless, due to the unpredictable departure of peers and the real time constraint of the consumed data, the problem of maintaining data availability remains open. In this paper we propose to set up a cache to save the "last part" of the "now playing" videos. We demonstrate that such a cache can enhance the data availability in these systems while introducing an acceptable additional traffic. Additionally, we develop a cache management policy that automatically adapts the size of the cached data to the system workload. The simulations we conducted show the effectiveness of our approach.