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BACKGROUND

Peer-to-peer (P2P) systems employ a network which con nects participating machines having equal or similar capabili ties and responsibilities. These systems perform tasks without the coordination of a conventional server (or with minimal set-up coordination by a server). A P2P network is a distributed system, without any cen tralized control or hierarchical organization, in which each node runs software with equivalent functionality. The current Internet is composed of two components: end hosts and rout ers. The end hosts use the routers to deliver data packets to each other. The role of the routers is to store and forward the data packets for the end hosts. The end hosts in general do not forward packets for other end hosts in this model. As seen in FIG. 1a, a P2P network is an overlay network constructed with a variety of wired and wireless end hosts, where each end host will forward packets for other …