Book excerpt: Peer-to-Peer (P2P) networks enable users to directly share digital content (such as audio, video, and text files) as well as real-time data (such as telephony traffic) with other users without depending on a central server. Although originally popularized by unlicensed online music services such as Napster, P2P networking has recently emerged as a viable multimillion dollar business model for the distribution of information, telecommunications, and social networking. Written at an accessible level for any reader familiar with fundamental Internet protocols, the book explains the conceptual operations and architecture underlying basic P2P systems using well-known commercial systems as models and also provides the means to improve upon these models with innovations that will better performance, security, and flexibility. Peer-to-Peer Networking and Applications is thus both a valuable starting point and an important reference to those practitioners employed by any of the 200 companies with approximately $400 million invested in this new and lucrative technology. - Uses well-known commercial P2P systems as models, thus demonstrating real-world applicability. - Discusses how current research trends in wireless networking, high-def content, DRM, etc. will intersect with P2P, allowing readers to account for future developments in their designs. - Provides online access to the Overlay Weaver P2P emulator, an open-source tool that supports a number of peer-to-peer applications with which readers can practice.