To understand how BitTorrent works and why it is different from traditional client-server network, let's examine what happens when you download a file from a Web site. This process follows traditional client-server architecture. The transfer speed is affected by mainly by the amount of traffic on the server and the number of other computers that are downloading the file. If the file is both large and many clients are getting the file from it, the load on the server will be huge and downloads are mostly likely to slow down.The Solution - Bittorrent Peer-to-Peer Network
Bittorrent uses Peer-to-Peer protocol and is different from traditional file distribution.The way Peer to Peer works is that people who want a file and people who have a file are all linked up together. Bits and pieces of the file are swapped around until they all have a complete copy.Let's say that Client A has the whole file, while clients B and C want it. A good P2P system will have client A feeding the first 1/2 of the file to client B, the second 1/2 to client C.. Then, while that's happening, clients B and C feeding each other bits of what they've downloaded from client A.
This speeds up the process, because instead of clients B and C receiving the file at 1/2 the speed that client A can deliver it, they're getting that, plus a portion of the speed each of the other two can deliver the file. So, all things being equal, it can double or triple the download speed for B and C.
The whole idea of P2P is that there's never a centralized location for a file and file transfer load is distributed across computers sharing the file. It resides in whole on at least one computer in the sharing network and in whole or in part on all the rest. Then the people who are downloading the file can get pieces of the file from others in the network until each one has a complete copy. The more people in the network and the more people with a complete copy, the faster the sharing goes.
Advantages of Bittorrent
- Most Bittorrent clients and servers are not only freeware and contain no spyware and ads but are also Open Source and avaible for editing.
- No leeching is permitted. Your download speed is dependent on the files that you have and upload speed to the peers.
- Unlike KaZaA and Napster, there's no underlying network of nodes or servers which can be shut down. As long as torrents are made and distributed, and trackers remain online, BitTorrent will continue to run.
- It alleviates server strain of the transfer load as described above.
- You have to upload as well as download. All BitTorrent clients which allow throttling will adjust your download throttle to match your upload throttle: if you're not letting people download from you then you won't be allowed to download from them.
- Not searchable. Big sites full of torrents are easy to find, but no single site carries all the torrents. You may have to actually do some looking before you can find what you want.
- BitTorrent is good for downloading stuff which is popular now, because the number of seeds and peers will be large. Old, obscure and non-mainstream material, on the other hand, is difficult to find.
- BitTorrent is totally public and hence insecure. While nobody can use it to send you viruses or anything like that, your IP address is visible to everybody else using the torrent. If you're using BitTorrent illegally, you can be tracked down easily.
Large files distribution such as Linux operating system images and legal blu-ray movies from Hollywood studios are what I see Bittorrent being used for extensively from now to the near future. It also serves as content distribution for TV broadcastor to deliver shows to a wider audience. CBC became the first public broadcaster in North America to make a full show available on torrent in 2008. The proliferation of Bittorrent is so fast that even government has adopted bittorrent to distribute tax and government budget information. In terms of commericial use, Blizzard Entertainment has been one of the most successful companies so far. They use their proprietary Bittorrent client to distribute games content and the actual games without incurring too much traffic costs. These are just the most obvious uses. As more people use Bittorrent and become comfortable with it, they will begin using it in entirely new ways.
Bittorrent Clients
uTorrent (http://www.utorrent.com)
Small enough to run off a USB key, but powerful enough to download any torrent in a jiffy (if it's got enough seeders), uTorrent is easy on the eyes and smart on your network. The memory footprint for uTorrent is very small, and system resources are barely touched. While you're torrenting, you shouldn't be surprised to find that other programs that use your Internet connection slow down, but the latest version of uTorrent has an answer to that. Called uTorrent Protocol, or uTP, it's a built-in throttling that detects network congestion and slows down the torrent until the traffic jam has dissipated.
It includes a transfer cap, so that users who have had limits imposed by their Internet Service Providers can keep track and automatically kill torrenting when that limit is reached. Skins have also been introduced, but there's no skins option in Preferences: instead, you must go to the uTorrent site and download and install them yourself. That's unnecessarily irritating.
Transmission (http://www.transmissionbt.com/)
Transmission is one of the very best choices for a free BitTorrent client on the Mac, being both extremely lightweight (some users even manage to run the Ubuntu version on their cell phones!) and fairly feature-packed. Transmission's interface is easy to use--and easy on the eyes--and this open-source app provides a whole host of clever features and flexible settings, especially when it comes to managing your bandwidth.
Transmission sets initial preferences so things "Just Work", while advanced features like watch directories, bad peer blocking, and the web interface can be configured with just a few clicks. Macworld put it this way: "It's fast, it's extremely lightweight, and -- even though it's available for a variety of platforms -- it behaves just as you'd expect a Mac program to."
Controversy
We've established that BitTorrent is a good way to get content to lots of people in a short space of time without expending huge amounts of bandwidth. What we also find is that BitTorrent is a great way to distribute copyrighted material.
It works like this. Instead of it being something legal (a game patch or the latest Linux distribution), the file being distributed can easily be illegal, or at least of dubious legality (an album (you can distribute many files at once using the same torrent), the CD or DVD images of a new game, a movie). And instead of some reputable companies or a Linux developer group, the person who makes and distributes the relevant torrent and maintains the tracker can be anybody. There are in fact a bundle of groups of individuals which churn out tonnes of these torrents.
Distributing the torrents for these movies/games/videos becomes a little more complicated as, while technically a site providing torrents isn't directly providing any copyrighted material, it is still legally very dodgy ground. Various jurisdictions have pursued legal action against websites that host BitTorrent trackers.There are a whole bunch of sites dedicated to circulating these torrents, but finding them isn't trivial.
Interesting Facts
Largest Torrent - There are several huge torrent files active at the moment, but the record goes to a torrent with a 746.70 GB collection of all the 2010 World Cup soccerr matches (~ 6GB per half match). This torrent couldnt even fit into the harddisks available in the market before year 2007.
Oldest Torrent - The torrent file that has been around for the longest time according to our knowledge is The Matrix ASCII. The torrent file in question was created in December 2003 when sites like isoHunt, The Pirate Bay and Torrentz.com were only a few months old and when Facebook and YouTube didn't yet exist. Thus far, this torrent has survived a mind boggling 2500 days.
Largest Swarm - We know that BitTorrent is used by millions of people, but which torrent was shared by the most people at once? According to our records this honor goes to the first episode of Heroes season 3, which appeared on BitTorrent September 23, 2008. It had a swarm (seeders + leechers) of 144,663 peers, a record that hasn’t been broken since. Today, most than two years later the episode has been downloaded more than 7 million times and at the time of writing it is still active.
Most Data Transferred - The final record we will discuss is the torrent that has resulted in the transfer of the most data. This record goes to a release of Blizzard’s StarCraft 2 which came out three months ago. The most popular torrent file for this 7.19 GB game has been downloaded 2.3 million times, totalling a massive 15.77 Petabytes.
References
RIAA sues an Iguana for using BitTorrent?, http://www.zeropaid.com/news/8464/pic_riaa_sues_an_iguana_for_using_bittorrent/
HowStuffWorks - How Bittorrent Works, http://computer.howstuffworks.com/bittorrent3.htm
5 Torrent Files That Broke Mind Boggling Records, http://torrentfreak.com/5-torrent-files-that-broke-mind-boggling-records-101107/
How Bittorrent Works, http://qntm.org/bittorrent
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