Peer-to-peer power

(CNN) -- Programs such as Napster are typically called peer-to-peer networking, as the programs link individuals users directly to share files rather than compiling files that are placed on a server for downloading. Here is a brief look at four different applications, including Napster, although dozens of programs have been released onto the Internet.

Aimster

Aimster piggybacks onto the immensely popular AOL Instant Messenger service by enabling AIM users to search for and share files. Aimster users also only share files with members of their AIM buddy list, and the program doesn't open up a user's hard drive to the entire network. Aimster restricts users to searching on the Gnutella file sharing network and the computers of other AIM users who have also customized AIM with Aimster. But plug-ins are in the works for the instant messaging programs offered by the Microsoft Network and Yahoo, ICQ, Napster/OpenNap and other networks. Aimster was developed by a group of programmers in Troy, New York.

Napster

Napster is the program that pushed peer-to-peer networking into the spotlight by allowing users to exchange MP3 files directly with each other. It uses a centralized method in which servers at Napster's headquarters contain members' registrations, shared file lists and music searches. When a member logs on via the Napster client software, a list of the member's music files available for sharing is uploaded to the server. Members can search for a file, but when they click on one to download, they are downloading the files directly from each other's computers, using their own disks and bandwidth. The Napster client also transmits back to Napster's servers a member's user name, IP address and the song that was downloaded.

The program's name is a reference to founder and original programmer Shawn Fanning's perpetually nappy hair. Napster has been massively successful, attracting more users in a shorter amount of time than any other Web site in history. It's extremely popular among college students, who used up so much bandwidth that the program was banned at 40 percent of U.S. colleges. Napster is available for both Macintosh and Windows users. Copycat programs are available for other operating systems, such as Unix or Linux.

Web site: http://www.napster.com

Gnutella

Gnutella is software that is designed, unlike Napster, not to be shut down, and it works for all files, not just MP3s. It is fully decentralized and doesn't rely on any central servers. The Gnutella application on your desktop acts as both a client and a server (or "servant") when interacting with other users on the Gnutella network, so Gnutella users communicate directly with each other and download directly from each other. So if any part of a Gnutella network is shut down, the rest will continue running. When a user sends a request for a particular file, it travels throughout the Gnutella network. When it reaches a computer that has the file, Gnutella connects the two computers directly. The program also handles file downloading by sending the request for a file in the same way a browser sends a request for a Web page, another reason Gnutella networks are hard to shut down because their file transfers resemble ordinary Web traffic.

But Gnutella's decentralized design includes drawbacks. For users, the lack of a central server means the system is less efficient as users chew up bandwidth attempting to trade files. For a business use, the decentralized approach means there is really no way of building user relationships or collecting revenue.

The original Gnutella was designed by programmers at AOL's Nullsoft division (also the developers of the popular Winamp MP3 player). They released the program on March 14, 2000, and immediately were deluged by people attempting to download it. AOL quickly pulled the plug, yanking the program from NullSoft's servers within hours of its release. But the original program was quickly reverse-engineered by other programmers, and multiple clones of the original have since been posted on the Internet. The name, by the way, is a homage to Nutella, a tasty chocolate-hazelnut spread popular in Europe, and the GNU project of the Free Software Foundation.

Web site: http://gnutella.wego.com/

Freenet

Freenet was specifically designed to avoid any kind of centralized control or administration so information can be published without identifying its source or its physical location. According to the Freenet Web site, the Freenet Network consists of many computers on the Internet each running a piece of software called the "Freenet Server" or "Freenet Daemon." This piece of software allows that computer to become a "node" in the Freenet, a small but equal part of the whole network. This node may store some information itself, and it may know something about some of the other nodes in the Freenet, but no one node knows about the entire system, and no one node is superior to any other. Freenet's Web site calls the network "a perfect anarchy." The network does not have any kind of search function.

The Freenet concept was originally created by Irish programmer Ian Clarke when he was a student at the University of Edinburgh in Scotland with the goal of creating a way to publish or share information without fear of censorship of any kind.

Web site: http://freenet.sourceforge.net/