Peer-to-peer file-sharing

Looking forward to watching a much-awaited movie you missed at the theatres? For most of us have, BitTorrent is the easiest and most convenient way to download them. As simple as it seems to us, however, the entire process is not as simple as it looks. And, it is quite a unique process. It involves a method of file sharing called peer-to-peer sharing. Let’s look into this process that many of us use so frequently, to see how it works. Peer-to-peer file sharing is different from conventional file downloading methods, in the sense that here, the different computers accessing the network serve as the source and destination of information simultaneously. The various servers using the network, called peers, use a software, rather than a web browser, to locate files that they are looking for, on other systems. Peer-to-peer file sharing started becoming prominent in the late1990’s, with the introduction of Napster, a file sharing application with some central servers that linked source and destination systems. After Napster was shut down, the most popular peer-to-peer services were Gnutella and Kazaa. These were more improved versions since movies and games could be downloaded in addition, while Napster allowed only music files. Napster and eDonkey2000, both of which worked using the central server-based model, were the first generation of P2P systems. Since these systems were primarily dependent on the working of the central servers, they were susceptible to centralized shutdown. The second generation of P2P file sharing encompassed networks like Kazaa, Gnutella and Gnutella2, which were not dependent on any central servers, thus connecting users directly to one another. The third generation of filesharing network used Freenet, which provides user anonymity besides independence from central servers. The BitTorrent protocol is special in many ways. Basically, it is dependent on central servers, like in the first generation, called trackers. However, it does not form what we might term as a conventional network. Instead new, separate networks are created for a definite group of users, for every set of files, called a torrent. Users are asked to upload an index file with the files they want to share to the website, where they are shared with others.

The mechanism of peer-to-peer file-sharing works in a unique way. The user has to run a peer-to-peer file-sharing software like Gnutella on their machine and send out a request for the file they would like to locate in the network. To locate the file, the software enquires with other machines connected to the network and finds out if any of them have the file in question. If the file is present in the memory of any of these machines, the download starts and the file is shared with the user placing the request. Now you know what exactly happens when you send out a request to download a file using BitTorrent. It’s fast, user-friendly, and consequently, very popular among most movie-freaks today, although it does bring into question issues like cyber security, copyright infringement, piracy and other legal issues.

This article was originally written by Shreyanka Dhar for the original Pragyan blog.