Many examples of P2P systems have emerged recently, most of which are wide-area, large-scale systems that
provide content sharing , storage services , or distributed “grid” computation [4, 11]. Smaller-scale P2P
systems also exist, such as federated, serverless ﬁle systems [2, 1] and collaborative workgroup tools . The success
of these systems has been mixed; some, such as Napster, have enjoyed enormous popularity and perform well at scale.