Gnutella ( with a silent g, or alternatively /gnʊˈtɛlə/) is a file sharing network. It is the most popular file sharing network on the Internet with a market share of more than 40%. In June 2005, Gnutella's population was 1.81 million computers.

History

The first client was developed by Justin Frankel and Tom Pepper of Nullsoft in early 2000, soon after the company's acquisition by AOL. On March 14, the program was made available for download on Nullsoft's servers. The event was prematurely announced on Slashdot, and thousands downloaded the program that day. The source code was to be released later, under the GNU General Public License (GPL).

The next day, AOL stopped the availability of the program over legal concerns and restrained Nullsoft from doing any further work on the project. This did not stop Gnutella; after a few days, the protocol had been reverse engineered, and compatible free and open source clones began to appear. This parallel development of different clients by different groups remains the modus operandi of Gnutella development today.

The Gnutella network is a fully distributed alternative to such semi-centralized systems as FastTrack (KaZaA) and Napster. Initial popularity of the network was spurred on by Napster's threatened legal demise in early 2001. This growing surge in popularity revealed the limits of the initial protocol's scalability. In early 2001, variations on the protocol (first implemented in proprietary and closed source clients) allowed somewhat of an improvement in scalability. Instead of treating every user as client and server, some users were now treated as "ultrapeers", routing search requests and responses for users connected to them.

This allowed the network to grow in popularity. In late 2001, the Gnutella client LimeWire became free and open source. In February 2002, Morpheus, a commercial file sharing group, abandoned its FastTrack-based peer-to-peer software and released a new client based on the free and open source Gnutella client Gnucleus.

The word "Gnutella" today refers not to any one project or piece of software, but to the open protocol used by the various clients. Since various parties are developing new clients, and the protocol will likely continue to evolve, it is hard to say what the word 'Gnutella' will come to mean in the future.

The name is a portmanteau of GNU and Nutella: supposedly, Frankel and Pepper ate a lot of Nutella working on the original project, and intended to license their finished program under the GNU General Public License. Gnutella is not associated with the GNU project; see GNUnet for the GNU project's equivalent.

How it works

To envision how Gnutella originally worked, imagine a large circle of users (called nodes), who each have Gnutella client software. On initial startup, the client software must bootstrap and find at least one other node. Different methods have been used for this, including a pre-existing address list of possibly working nodes shipped with the software, using updated web caches of known nodes (called GWebCaches), UDP host caches and, rarely, even IRC. Once connected, the client will request a list of working addresses. The client will try to connect to the nodes it was shipped, as well as nodes it receives from other clients, until it reaches a certain quota. It will only connect to that many nodes, locally cache the addresses it has not yet tried, and discard the addresses it tried that were invalid.