The term "peer-to-peer" has come to be applied to networks that expect end users to contribute their own files, computing time, or other resources to some shared project. Even more interesting than the technology's technical underpinnings is its socially disruptive potential: in various ways these systems return content, choice, and control to ordinary users. This book presents the goals that drive the developers of the best-known peer-to-peer systems, the problems they've faced, and the technical solutions they've found. The contributors are leading developers of well-known peer-to-peer systems, including Popular Power, Jabber, Gnutella, FreeNet, SETI@Home, Red Rover, Publius, Free Haven, and Groove Networks. Topics include the Internet as a collection of conversations, metadata, performance, trust, accountability, security, and gateways between systems.