A central server can become a bottleneck and a single point of failure. Every client depends on the same place for bandwidth, storage, and compute. For workloads like file sharing or large-scale streaming, that central point can quickly become the limit.

Peer-to-peer architecture spreads the work across the participants. Each node, called a peer, can both use resources and provide resources. A peer might download a file from one machine while uploading another part of that file to someone else.

This can reduce pressure on central servers, but it adds new problems. Production P2P systems still need to help peers find each other, connect through firewalls, verify data, handle peers leaving, and protect the network from abuse.

This chapter explains P2P architecture, how peers find and talk to each other, common network designs, Distributed Hash Tables, content lookup, data distribution, security, peers joining and leaving, and modern use cases.