Bored up with technical updates :( We can see the working of some famous websites

Today we can see working of BitTorrent.

Before moving on to the working principles some of the frequently used words in torrent are to be discussed.

1. Peer: A peer is one instance of a BitTorrent client running on a computer on the Internet to which other clients connect and transfer data. Depending on context, "peer" can refer either to any client in the swarm or more specifically to a downloader, a client that has only parts of the file....
2. Seed: A seed refers to a machine possessing some part of the data. A peer or downloader becomes a seed when it starts uploading the already downloaded content for other peers to download from. This includes any peer possessing 100% of the data or a web seed.
3. Tracker: A tracker is a server that keeps track of which seeds and peers are in the swarm.          Clients report information to the tracker periodically and in exchange, receive information        about other clients to which they can connect. The tracker is not directly involved in the data  transfer and does not have a copy of the file.
4. Leeches: The term leech also refers to a peer (or peers) that have a negative effect on the swarm by having a very poor share ratio, downloading much more than they upload. Leeches may be on asymmetric Internet connections or do not leave their BitTorrent client open to seed the file after their download has completed. However, some leeches intentionally avoid uploading by using modified clients or excessively limiting their upload speed.
5. Swarm: Together all peers sharing a torrent is called swarm.

NOW MOVING ON TO WORKING PRINCIPLE,

Unlike some other peer-to-peer downloading methods, BitTorrent is a protocol that offloads some of the file tracking work to a central server (called a tracker). Another difference is that it uses a principle called tit-for-tat. This means that in order to receive files, you have to give them. This solves the problem of leeching. With BitTorrent, the more files you share with others, the faster your downloads are. Finally, to make better use of available Internet bandwidth (the pipeline for data transmission), BitTorrent downloads different pieces of the file you want simultaneously from multiple computers.

Here's how it works:

• You open a Web page and click on a link for the file you want.
•   BitTorrent client software communicates with a tracker to find other computers running BitTorrent that have the complete file (seed computers) and those with a portion of the file (peers that are usually in the process of downloading the file).
•  The tracker identifies the swarm, which is the connected computers that have all or a portion of the file and is in the process of sending or receiving it.
•  The tracker helps the client software trade pieces of the file you want with other computers in the swarm. Your computer receives multiple pieces of the file simultaneously.
• If you continue to run the BitTorrent client software after your download is complete, others can receive .torrent files from your computer; your future download rates improve because you are ranked higher in the "tit-for-tat" system.

Downloading pieces of the file at the same time helps solve a common problem with other peer-to-peer download methods. Peers upload at a much slower rate than they download. By downloading multiple pieces at the same time, the overall speed is greatly improved. The more computers involved in the swarm, the faster the file transfer occurs because there are more sources of each piece of the file. For this reason, BitTorrent is especially useful for large, popular files.