ABSTRACT
Peer-to-peer (P2P) systems have drawn much attention from end Internet users and the research community in the past few years. From Napster,1 the earliest P2P system, appearing in 1999, to popular systems such as Gnutella,2 Freenet,3 KaZaA,4 and BitTorrent,5 more and more P2P file sharing
systems come to fame. In research community, P2P has become one the most active research fields. Many universities and research institutes have research groups focusing on P2P techniques. And P2P has become one of the hottest topics at many conferences and workshops on distributed systems or networking.
