The Biggest BitTorrent Library in Thailand

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BitTorrent is a peer-to-peer file sharing (P2P) communications protocol. BitTorrent is a method of distributing large amounts of data widely without the original distributor incurring the entire costs of hardware, hosting and bandwidth resources. Instead, when data is distributed using the BitTorrent protocol, each recipient supplies pieces of the data to newer recipients, reducing the cost and burden on any given individual source, providing redundancy against system problems, and reducing dependence on the original distributor. The protocol is the brainchild of programmer Bram Cohen, who designed it in April 2001 and released a first implementation on 2 July 2001.[1] It is now maintained by Cohen's company BitTorrent, Inc. Usage of the protocol accounts for significant traffic on the Internet, but the precise amount has proven difficult to measure. There are numerous compatible BitTorrent clients, written in a variety of programming languages, and running on a variety of computing platforms.

A BitTorrent client is a program that downloads files using the BitTorrent protocol. The first client, known as BitTorrent, was created by Bram Cohen in the summer of 2002. Most of the other clients are based at least in part on BitTorrent, and even more are being created right now. The following tables compare general and technical information for a number of applications supporting the BitTorrent protocol. Please see the individual products' articles for further information. This article is neither all-inclusive nor necessarily up-to-date

The company has announced two revenue models: content aggregation at http://www.bittorrent.com where the company, on February 26, 2007, released a web-based store to distribute movies, TV shows, music and video games. The company also licenses its technology to websites "to add the speed and efficiency of patented BitTorrent technology to their current content delivery infrastructure, significantly reducing bandwidth costs while increasing capacity over standard HTTP delivery solutions." http://www.bittorrent.com/about The latter solution allows website developers to overlay their content delivery network (CDN) vendor with BitTorrent's P2P CDN, built on the company's widely used client software. One should be able to expect dramatic cost savings using P2P bandwidth relative to the cost of CDN bandwidth, however ISPs may view this as an unattractive application of their network capacity. In the words of the company's president: "BitTorrent has fundamentally changed the Internet by enabling high-speed and high-quality content distribution on the web," said Mr Navin. "Today we have announced the role BitTorrent.com will play as a hub for consumers to enjoy their favourite entertainment, but we see a future that involves BitTorrent's content delivery platform powering thousands of websites, including those of content creators themselves."

Creating and publishing torrents
The peer distributing a data file treats the file as a number of identically-sized pieces, typically between 64 kB and 1 MB each. A piece with size greater than 512 kB will reduce the size of a torrent file for a very large payload, but is claimed to reduce the efficiency of the protocol [1]. The peer creates a checksum for each piece, using the SHA1 hashing algorithm, and records it in the torrent file. When another peer later receives that piece, the checksum of the piece is compared to the recorded checksum to test that the piece is error-free.[3] Peers that provide a complete file are called seeders, and the peer providing the initial copy is called the initial seeder. The exact information contained in the torrent file depends on the version of the BitTorrent protocol. By convention, the name of a torrent file has the suffix .torrent. Torrent files have an "announce" section, which specifies the URL of the tracker, and an "info" section, containing (suggested) names for the files, their lengths, the piece length used, and a SHA-1 hash code for each piece, all of which is used by clients to verify the integrity of the data they receive. Completed torrent files are typically published on websites or elsewhere, and registered with a tracker. The tracker maintains lists of the clients currently participating in the torrent.[3] Alternatively, in a trackerless system (decentralized tracking) every peer acts as a tracker. This is implemented by the BitTorrent, ?Torrent, BitComet, KTorrent and Deluge clients through the distributed hash table (DHT) method. Azureus also supports a trackerless method that is incompatible (as of April 2007) with the DHT offered by all other supporting clients. In November 2006, BitTorrent Inc. introduced its "Publish Torrent" service, which creates and hosts a torrent file (seeded from an existing web-hosted media file) and tracks the downloads. The service (http://www.bittorrent.com/publish) requires a client that supports web-seeding (currently the official client, Azureus, ?Torrent and anything based on Libtorrent).

Downloading torrents and sharing files
Users browse the web to find a torrent of interest, download it, and open it with a BitTorrent client. The client connects to the tracker(s) specified in the torrent file, from which it receives a list of peers currently transferring pieces of the file(s) specified in the torrent. The client connects to those peers to obtain the various pieces. Such a group of peers connected to each other to share a torrent is called a swarm. If the swarm contains only the initial seeder, the client connects directly to it and begins to request pieces. As peers enter the swarm, they begin to trade pieces with one another, instead of downloading directly from the seeder. Clients incorporate mechanisms to optimize their download and upload rates; for example they download pieces in a random order to increase the opportunity to exchange data, which is only possible if two peers have different pieces of the file. The effectiveness of this data exchange depends largely on the policies that clients use to determine to whom to send data. Clients may prefer to send data to peers that send data back to them (a tit for tat scheme), which encourages fair trading. But strict policies often result in suboptimal situations; e.g., when newly joined peers are unable to receive any data because they don't have any pieces yet to trade themselves or when two peers with a good connection between them do not exchange data simply because neither of them wants to take the initiative. To counter these effects, the official BitTorrent client program uses a mechanism called “optimistic unchoking,” where the client reserves a portion of its available bandwidth for sending pieces to random peers (not necessarily known-good partners, so called preferred peers), in hopes of discovering even better partners and to ensure that newcomers get a chance to join the swarm.[4]