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This model of network arrangement differs from the client-server model where communication is usually relayed by the server. A typical example for a non peer-to-peer communication is email, where the email is transmitted to the server for delivery, transmitted to the destination between servers, and is fetched later by the receiving client. A direct transmission from a client to another client is often impossible. In a peer-to-peer network, any node is able to initiate or complete any supported transaction with any other node. Peer nodes may differ in local configuration, processing speed, network bandwidth, and storage quantity. One of the first uses of the phrase "peer to peer" is in 1984, with the development of the "Advanced Peer to Peer Networking" architecture at IBM.
Different peer-to-peer networks have varying P2P overlays.
Note: The initialism P2P is often confused to refer to Point-to-Point, as used in telecommunications. More correctly, it should be used to refer to Peer-to-Peer connections.
Although the term may technically be applied to any number of networking technologies and applications that use this model (such as the NNTP protocol used for transferring Usenet news, SMTP for mail transactions, ARPANET, decentralized live chat Java applets or BBS FidoNet), it is most frequently used to refer to file sharing networks such as Gnutella, FastTrack, and the now-defunct NapsterNapster is an online music service that was originally a file sharing service created by Shawn Fanning. Napster made a major impact on the Internet scene during the year 2000. Its technology allowed music fans to easily share MP3 format song files with ea, which provide facilities for free (and somewhat anonymous) file transfer between personal computers connected to the InternetThis article is about the Internet the extensive, worldwide computer network available to the public. An internet is a more general term for a set of interconnected computer networks that are connected by internetworking''. WWW information network structu.
Some networks and channels, such as Napster, OpenNap, or IRC @find, use a client-server structure for some tasks (e.g. searching) and a peer-to-peer structure for others. Networks such as Gnutella or Freenet, use a peer-to-peer structure for all purposes and are referred to as true peer-to-peer networks.
An important aspect in peer-to-peer networks is that the bandwith of all clients can be fully used, so the total bandwidth - and usually the available download bandwith for the average user - grows with the number of nodes, instead of all clients having to share the (limited) bandwidth of the server (so that more clients would mean slower data transfer for all users).
When the term peer-to-peer was used to describe the Napster network, it implied that the peer protocol nature was important, but in reality the great achievement of Napster was the empowerment of the peers (i.e., the fringes of the network). The peer protocol was just a common way to achieve this.
The peer-to-peer paradigm has been used to deploy publish/subscribe systems, i.e, a system where users subscribe with a continuous query and asychronously receive notifications when matching events take place. One example of such publish subscribe system is P2P-DIET .