What is Peer-to-peer?

A peer-to-peer (or P2P) computer network is a network that relies on the computing power and bandwidth of the participants in the network rather than concentrating it in a relatively few servers. P2P networks are typically used for connecting nodes via largely ad hoc connections. Such networks are useful for many purposes like sharing content files containing audio, video, data or anything in digital format, and real-time data, such as Telephony traffic. And, the decentralized nature of peer-to-peer file sharing removes the need for a central server, and removes the possibility of centralized control.

When you install a software such as Napster or Kazaa on your computer and access the internet, it connects to other computers to download any stuff that you search using the client.

A pure peer-to-peer file transfer network does not have the notion 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 for a non peer-to-peer file transfer is an FTP server. One user uploads a file to the FTP server, then many others download it, with no need for the uploader and downloader to be connected at the same time.

Some networks and channels, such as Napster (now closed), 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 sometimes referred to as true peer-to-peer networks, although Gnutella is greatly facilitated by directory servers that inform peers of the network addresses of other peers.

Peer-to-peer file sharing networks are more resistant to legal attacks, because there is no one central entity to file a lawsuit against. To attack a peer-to-peer file sharing network, a claimant must file suits against individual network users.

Three major types of P2P network are:

Pure P2P:

Peers act as clients and server
There is no central server
There is no central router

Hybrid P2P:

It has a central server that keeps information on peers and responds to requests for that information.
Peers are responsible for hosting the information as the central server does not store files, for letting the central server know what files they want to share and for downloading its shareable resources to peers that request it.
Route terminals are used addresses, which are referenced by a set of indices to obtain an absolute address.

Mixed P2P:

Has both pure and hybrid characteristics

Peer-to-Peer File Sharing Networks

There are many peer-to-peer file sharing networks in operation. The main peer-to-peer file sharing networks are Gnutella, DirectConnect, eDonkey2000, FastTrack, and OpenNap.

Peer-to-Peer File Sharing Clients

Peer-to-peer file sharing clients will often change support for peer-to-peer file sharing networks. A few peer-to-peer clients support more than one network.