The History of Peer to Peer Networks

File sharing is the process by which internet users can exchange photographs, mp3 files, documents and other pieces of digital information. Virtually all file sharing programs rely on a peer to peer network (P2P). In this model, users of the network not only receive, or download content, but also store and provide (upload) content to other users. Thus, each computer within the network serves as both client and server, thereby distinguishing P2Ps from the more traditional internet model in which a personal computer functions as a client requesting information from a web-host. P2Ps serve content from individual users' own computers to any other unit (known as a node) that requests the material. Recent surveys have estimated that P2P file-sharing accounts for between 50 and 90% of all internet traffic. -1 This enormous percentage elucidates the significant and steady growth file-sharing P2Ps have experienced since their inception in 1999. - 2 In the succeeding nine years, the structure of P2Ps has evolved significantly.

Napster - The Beginning

Perhaps the most famous and certainly the first large scale P2P was Napster. Developed by 18 year old Shawn Fanning, Napster allowed users to search for and exchange music directly with each other, rather than relying on the central server of a website such as mp3.com, whose files were often deleted by the RIAA for copyright infringement. Napster, however, was not a true P2P, but a hybrid. The MP3's themselves were stored on individual nodes. Other nodes downloaded the files directly from the individual's computer. However, all MP3s on the Napster network were indexed on a central server. In order to download the file, one would have to query the central server to locate a node that hosted the desired song. Once the RIAA obtained the legal order to shut down Napster's central server for copyright infringement, the service shut down, because, while individuals retained their libraries, they could no longer share their songs or search for other people's music. Thus, the existence of a central server created one bottleneck of information that destroyed the whole network the minute it was closed.

Gnutella - Most Popular File Sharing Network

While modern examples of a server-based index P2P include Soulseek and iTunes - 3, P2Ps generally advanced beyond the Napster model after July 2001. Justin Frankel of Nullsoft created the first example of the second generation P2P technology. He called his network Gnutella, and it remains the most popular P2P today. - 4 Like Napster and other central-server database P2Ps, Gnutella requires users to store their files on their own computers are share directly with other nodes. Also, Gnutella users must download an appropriate application, such as Limewire, BearShare or Morpheus, in order to access the P2P. Gnutella differs from the Napster model in the way members search for songs. As no central database stores a list of all available songs, nodes must instead query all other nodes presently on the network for any given song. Nodes continue contacting each other for a specific period of time, during which an average of six or seven propagations of the query occur. Even if a user's particular node can detect only four other machines on the network, at that continued rate of propagation, any given query would reach between 8,000 and 10,000 computer hard drives by the end of the query. Originally, Gnutella users suffered from bandwidth issues, as all nodes were treated equally and therefore shouldered a large (and equal) amount of the network's staggering bandwidth needs. Eventually, however, Gnutella restructured its network to allow users with high bandwidth ratings to be classified as “Super Node,” or a node through which many nodes with lower bandwidth ratings connect. The use of Super Nodes as information hubs reduces the amount of bandwidth that normal nodes use.

ANts - Anonymous Peer-to-Peer Open Source File Sharing

The third generation of P2P looks much like Gnutella, but with greater privacy protection. Applications such as ANts P2P route file sharing requests through other users' clients, who function as network nodes. In essence, ANts and similar P2Ps are friend-to-friend networks, because no one can access a computer's hard drive unless the owner has listed that foreign node as a friend. Computer A could give a file to a friend, Computer B, who could then share it with Computer C, but Computer C could not directly access Computer A because the two would not be “friends.” Unfortunately, this type of network has not caught on in most places because their privacy features (going through the network nodes instead of downloading directly from foreign nodes) use too much bandwidth and are difficult for many people to utilize properly.

BitTorrent - P2P Communications Protocol

The fourth generation of P2P technology has been the ability to stream media using technology called Bit Torrent. The network's main advantage is that it uses a central server to locate all other Bit Torrent clients currently online. Next, that server searches each client for all or part of a file that a user has requested. Finally, each of those clients uploads a part of the file to the requesting user. Bit Torrent also features “tit for tat” technology, which tracks how often users allow other nodes to download content from their computers. The more often a user allows others to download, the faster that user is able to download in the future. This innovation allows faster download times, as most personal computers can download faster than they can upload. Thus, when one computer is downloading directly from another, the uploading computer actually determines the transfer pace. By encouraging users to leave Bit Torrent running, the company allows any one user to download from multiple nodes at once, thus speeding the transfer pace to the rate at which the downloading node is capable of accepting the transfer. Due to the fast file transfer rate afforded by the multiple-uploading node technology, Bit Torrent enables live streaming television and radio for its clients, in addition to the transfer of large files like books, lengthy legal documents and even uploading large movies.

---

Sources