Peer-to-Peer Communications (Linktionary term)

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Peer-to-Peer Communications

Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

This topic discusses various forms of peer-to-peer communications, including peer communications in the OSI protocol stack, traditional peer-to-peer networking (as compared to client/server networking), and community-based P2P (peer-to-peer) networking techniques made famous by Napster.

See Peer-to-Peer and Tom Sheldon's "Napster Disruption" article for more information.

In the world of political negotiations, "peer to peer" refers to communications between diplomats of the same rank. In the networking environment, "peer to peer" refers to communications between similar processes running in different computers, or communication between devices that are equal with regard to how they exchange information and control communications.

The OSI protocol stack provides a commonly accepted layering of communications processes. The bottom layer defines physical connections, while the top layer defines applications processes. In between are connectionless and connection-oriented communication processes that establish connections between two points (data link layer) or across internetworks. A conversation takes place between peer protocol layers in each system. For example, transport protocols in one system exchange information with transport protocols in the other system. See "Network Architecture" for more information.

"Peer to peer" also refers to network communications that bypass servers and allow hosts to directly communicate. This is significant in enterprise networks where most exchanges take place through servers (i.e., the client/server model). Windows 9x includes peer-to-peer networking support that allows any host to establish a communication session with an equal relationship with another host. There is no need to go through a server. In the client/server architecture, clients must contact a server that usually controls access and message exchange.

P2P, Napster, and Edge Networking

P2P refers to peer-to-peer "community-oriented" information exchange tools that were popularized when Napster hit the scene. While the Napster trend started as a way to exchange MP3 music files, it has since turned into a sophisticated networking technology that helps users locate information on other user's computers and access it directly.

The P2P concept is that information is stored on user's computers. With software like Napster and Gnutella, users search for a song and the software displays a list of peers who have the song stored on their computers. The locations are displayed and the user selects the closest site or the site with the best download speed or music quality. Flycode (started by early Napster founders) describes its peer-to-peer software as software that connects members' hard drives to create a global, virtual library of noninfringing content. When a member requests a specific piece of digital content, Flycode sends him or her directly to another member's hard drive within a matter of seconds to retrieve the file.

P2P promotes a network storage model different from the traditional Web server storage model. End users host personal collections of music, electronic books, videos, photographs, technical information, software drivers, and so forth, on their own computers. Information is widely distributed, rather than stored on a relatively few servers. User computers become servers, or what some have called "media collection devices." This distributed file sharing concept is not new. It has been around for some time in collaborative software and Microsoft Windows' peer-to-peer networks. What Napster did was introduce software that simplified peer-to-peer indexing, searching, and content distribution among users without any controls imposed by network administrators (or the owners of copyrighted material, but that is another story). Software features quickly expanded to support instant messaging, advanced searching, and mailing list support.

In the enterprise (and on the Internet), peer-to-peer networking bypasses the central control that administrators have over information that is stored on file servers. Consequently, P2P has been called "server bypass" technology. While administrators normally prefer that all information access be handled by servers for security and control reasons, some administrators like the P2P concept because it reduces the traffic load on busy centralized servers. That in itself makes P2P a viable networking concept. However, it also opens users up to hacker attacks since connections and exchanges are not protected by traditional server-based security mechanisms. Still, P2P is not going away soon.

Users in departments or workgroups often need to share similar information. If they are connected to the same LAN segment, traffic stays local if they are sharing it off their own storage devices. In a wireless environment, users may be able to directly connect with one another and exchange files, thus keeping traffic completely off local networks or the Internet. In a hybrid approach, P2P software helps users locate the files they need on a nearby computer that is accessible via wireless connections. In some cases, a Web server may instantly move that information to a nearby server so the end user can access it using a short-distance Bluetooth wireless connection. Thus, P2P promotes networking at the edge.

Developers are using the P2P concept as the basis for new collaboration software and automatic software distribution. P2P is also finding its way into online user-to-user swap meets, product exchanges, and auctions.

See the section "Internet Distributed File Sharing" under the topic "File Sharing" for more information, and a list of P2P software and information sites. Also see the topic "Distributed Computer Networks."