Peer-to-peer Guide, Meaning , Facts, Information and Description
Generally, a peer-to-peer (or P2P) computer network is any network that does not rely on dedicated servers for communication but instead mostly uses direct connections between clients (peers). A pure peer-to-peer network does not have the notion of clients or servers, but only equal peer nodess 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 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.
Usage of the term
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 Napster, which provide facilities for free (and somewhat anonymous) file transfer between personal computers connected to the Internet.
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.
Some people describe peer-to-peer file-sharing networks by their 'generation'. In this context, they are referring only to the popular internet-based file-sharing networks, not earlier research- and business-oriented peer-to-peer systems, which pre-date them.
The first generation of peer-to-peer networks had a centralized file list, like Napster. Ultimately courts in the United States ruled that this was an infringement of copyright.
The second generation of peer-to-peer networks had decentralized file lists, such as Gnutella and FastTrack.
Also usually included in the second generation are improvements like distributed hash table networks, and other optimizations of decentalized search.
The third generation of peer-to-peer networks are improvements upon generations one and two with anonymity features built in. Examples of anonymous networks are Freenet, I2P, GNUnet, and MUTE / AntsP2P.
Consequently, peer-to-peer networks have been targeted by industry trade organizations such as the RIAA and MPAA as a potential threat. The Napster service was shut down by an RIAA lawsuit; both groups the RIAA and MPAA spend large amounts of money attempting to lobby lawmakers for legal restrictions. A bill introduced by California Representative Berman, which would have granted copyright holders the legal right to break into computer systems believed to be illegally distributing copyrighted material, and to subvert the operation of peer-to-peer networks, was defeated in committee in 2002. However the 'INDUCE Act' currently making its way through Congress could do severe damage to the peer-to-peer community in the United States (and according to its opponents has implications for just about every piece of technology in modern life).
As attacks from media companies expand, the networks have seemed to adapt at a quick pace and have become technologically more difficult to dismantle. This has caused the users of such systems to become targets. Some have predicted that open networks may give way to closed, encrypted ones where the identity of the sharing party is not known by the requesting party. Other trends towards immunity from media companies seem to be in wireless adhoc networks where each device is connected in a true peer-to-peer sense to those in the immediate vicinity. (See Wireless Mesh Networking)
Anonymous peer-to-peer networks allow for distribution of material - legal or not - with little or no accountability for it. Many people believe this will lead to trading of child pornography and facilitate terrorism, and call for its regulation on those grounds. Others counter that the potential for illegal uses should not prevent the technology from being used for legal purposes, and the presumption of innocence should apply. They may also question the legitimacy of these fears, citing anti-communist and anti-homosexual "scares" of earlier times.
Many P2P systems use stronger peers (super-peers, super-nodes) as servers and client-peers are connected in a star like fashion to a single super-peer.
Sun added classes to the Java technology to speed the development of peer-to-peer applications quickly in the late 1990s so that developers could build decentralized real time chat applets and applications before Instant Messaging networks were popular. This effort is now being continued with the JXTA project.
Peer-to-peer systems and applications have attracted a great deal of attention from computer science research; some prominent research projects include the Chord lookup service, ARPANET, the PAST storage utility, the P-Grid, a self-organized and emerging overlay network and the CoopNet content distribution system (see below for external links related to these projects).
P2P can also stand for Pay-to-play (as in Pay-to-play/P2P games).
This is an Article on Peer-to-peer. Page Contains Information, Facts Details or Explanation Guide About Peer-to-peer Generational classification of peer-to-peer networks
First generation
Second generation
Third generation
Legal controversy
The most commonly shared files on such networks are mp3 files of popular music and DivX movie files. This has led many observers, including most media companies and some peer-to-peer advocates, to conclude that these networks pose grave threats to the business models of established media companies. One of the most famous leaks was unreleased Madonna songs including her 2000 hit "Music" prior to its official commercial release.Computer science perspective
Technically, a true peer-to-peer application must implement only peering protocols that do not recognize the concepts of "server" and "client". Such pure peer applications and networks are rare. Most networks and applications described as peer-to-peer actually contain or rely on some non-peer elements, such as DNS. Also, real world applications often use multiple protocols and act as client, server, and peer simultaneously, or over time. Completely decentralized networks of peers have been in use for many years, two examples include USENET (1979) and FidoNet (1984).Networks, protocols and applications
Format:
All networks and protocols are in alphabetical order except very similar applications which are listed in one entry with the most important one first, determining the place of this very similar applications in the list.
An earlier generation of peer-to-peer systems were called "metacomputing" or were classed as "middleware". These include:Multi-network applications
Format:
See also
External links
Computer science research