What is peer-to-peer (p2p)?
Peer-to-peer (or P2P) is a computer network architecture where computers use resources of network participants rather than conventional centralized resources. In a centralized architecture a relatively low number of servers provide the core value to a service or application.
P2P networks are typically used for connecting nodes via largely ad hoc connections. Such networks are useful for many purposes. Sharing content files (file sharing) that contain audio, video, data or anything in digital format is very common, and real time data, such as telephon traffic, is also transferred using P2P technology.
A pure P2P network does not use the concept of clients or servers but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network.
This model of network arrangement differs from the client-server model where communication is usually to and from a central server. A typical example of a file transfer that is not P2P is an FTP server where the client and server programs have separate roles: the clients initiate the download/uploads, and the servers respond to and meet these requests.
Advantages of P2P networks
In P2P networks, it is important that all clients provide resources, including bandwidth, storage space, and computing power. Thus the total capacity of the system increases with new clients.
This is not true of a client-server architecture with a fixed set of servers, in which adding more clients could mean slower data transfer for all users.
The distributed nature of P2P networks also increases robustness in case of failures by replicating data over multiple peers, and -- in pure P2P systems -- by enabling peers to find the data without relying on a centralized index server. In the latter case, there is no single point of failure in the system.