Research And Design On P2P Streaming Media Technology Based On PeerCast

In recent years, streaming media has gradually become the main consumption of the Internet. Conventional streaming media service mainly works by the "Client-Server" mode in which the server connects each client in a unicast way. However, as the information processed by the streaming media system is multimedia data which has the traits of high bandwidth and long duration, the resources like bandwidth, process ability and so on on the server side will be consumed away quickly, which becomes the bottleneck of the whole system. Therefore, researching P2P streaming media technology takes an important significance for solving the server side bottleneck problem in the streaming media application.In order to take a deep insight into P2P streaming media technology, this thesis has made an in-depth analyzation of the now most representative open-source project of P2P streaming media technology—PeerCast. In the condition of lacking correlative documents, its internal mechanism and realization principle is learned by using research methods like experimenting repeatedly, outputing logs and analyzing the codes and some problems with its disconnect&reconnect mechanism and node-selecting mechanism are discovered. To solve these problems, improved schemes are raised, and furthermore realized and tested.This thesis has mainly improved PeerCast from two aspects: the first is its disconnect&reconnect mechanism; the second is its node-selecting mechanism. According to the results of the disconnect&reconnect experiment, if one node in the data transmitting tree of PeerCast quits, the downriver transmitting tree will totally dismiss and all the downriver nodes begin to search for new sources respectively. This results into many problems: on one hand, the reconnecting time taken by each single node is long and the reconnecting success probability is low; on the other hand, it involves rebuilding the transmitting tree which will cause service quality instability of the whole network. In this thesis, an improved disconnect&reconnect scheme is raised and it is proved by time complexity comparison and results of comparative experiments that the improved scheme advance over the original scheme in the aspects of reconnection speed, reconnection success probability, network stability and so on. Besides, by analyzing the original node-selecting mechanism of PeerCast, it is discovered that the comparison parameter "numHops" used in the homo-category node selection only stands for the logical distance between nodes in the data transmitting tree; it doesn't stand for the actual physical distance between nodes. To solve this prolem, a node-selecting scheme based on physical delay is raised and furthermore realized and tested, in which the feasibility and superiority of the improved scheme is proved.In the end, the work done in this thesis is concluded and the further research work in the future is look forward.