BitTorrent is kollaboratives file sharing minutes, which are suitable particularly for the fast distribution of large files (beyond of 100 MT). The first implementation by the inventor Bram Cohen took place in the programming language Python. Meanwhile a set of alternative programs is available, which implement BitTorrent minutes.

The procedure of the data distribution with BitTorrent is in principle different from the function of the well-known file sharing exchange stock exchanges, with which each participant offers parallel own files. The application purpose is rather comparable with the traditional File Transfer Protocol or similar minutes for file transmission. By the increasing implementation of Trackern, trackerless enterprise as well as search functions in the Clients, these can be increasingly also used however like traditional exchange stock exchanges.

Function of BitTorrent Filesharing

In the comparison to the conventional Download of a file by HTTP or ftp with the BitTorrent technology the Upload capacities of the Downloader are along-used, even if they downloaded the file only incompletely. Files are not distributed thus any longer only star shaped by a server, but also from user to user it distributes (Peer ton Peer) whereby all can keep their files faster. The server is loaded and the offerers saves costs less. Altogether the Downloadlast is not smaller, it on the Clients is only shifted. This kind of the spreading becomes possible by the utilization of unused Upload capacities. With popular source files this technology prevents a breaking down of the net.

BitTorrent (which is called translated as many as "„rapid data stream"”) consists of two parts: The server program, called tracker, administers information to one or more files. The downloading Client experiences from the tracker, who downloads and distributes otherwise still the file. As soon as a Client a segment (chunk) of the file received and verified the check total, it announces this to the tracker and can this piece of file on to other Clients pass. One calls Peers, which are interested in the same Torrent, swarm. One calls Peers, which exclusively downloaden, more leecher (English "„Blutegel, blood Auger "“) and such those mainly uploaden, are called sea-that (English "“).

In order to be able to download a file, the Client needs a Torrent file (file dung .torrent or .tor). In this is the address of the tracker as well as file name, size and check totals of the file which can be downloaded. A Torrent file can contain also information about several files. Torrent files are large few kilobytes and lie usually on the homepage of the offerer ready for the Download. If the offerer deletes the Torrent from the tracker or if the contact is lost to the tracker, the Clients cannot develop a new contact to other Clients more, the exchange between already well-known Clients can however be continued.

Contrary to the well-known file sharing systems arbitrary files from the existence of the participants are not exchanged. Rather each swarm distributes only the files, which the author of the Torrent file planned explicitly for the Download. Also the operator of the tracker determines, which Downloads is to be administered by this. The individual tracker are not located in connection to each other, existed therefore no common net. Offerers can dissociate themselves in such a way from strange, possibly illegal, contents more easily.

In new versions "„trackerless "“(trackerless) systems were developed. The tracker function is taken over thereby by the Clients with. This avoids some the past problems (e.g. the missing reliability of the tracker), even if tracker-supported enterprise will be further possible. It facilitates also an offering, since tracker represent the part in BitTorrent. Since in November 2005 the version 4.2.0 appeared the reference Client supports the trackerless enterprise and sets thereby on the Kademlia algorithm. The tracker can thereby decentralized, similarly as in the Kad network, when Distributed Hash Table on the Clients (in the net) are put down and administered.

In the future the advancement of minutes is carried out no longer alone by Bram Cohen but also by other developers. BitTorrent users are lately increasingly affected by (partly unwissentlichen) the Traffic Shaping of their Provider. These use usually Sandivine/Ellacoya of systems or Cisco SCE 1000 series, which can sniffen deeply into the data traffic. If packages are classified as P2P-Pakete, the Upload is almost throttled on zero. When answer to it, and because Bram Cohen did not see a necessity, the Clients Azureus implemented and uTorrent a END END coding (RC4) over the Traffic Shaping to escape. BitComet supports the new minutes coding likewise.

Operational areas, pro and cons

BitTorrent for the fast distribution of large files is particularly well suitable, for which a up-to-date large demand is present. With somewhat older or less asked files the Download over ftp or HTTP is to be perhaps preferred because of that possibly to small number of Uploadern.

Since the quantity of the range, which can get each Downloader (Leecher), of the quantity of the finished and the quantity of the incomplete Downloads (sources) in the net, as well as the Uploadraten the user depends, it can depending upon quantity the offerer (Seeder), who too more or less comes Downloader (Leecher) and the distribution rate "“kilobytes per second"”. Since a user with complete Download needs practically no Download range, the maximally available range for the entire net rises, because this finished user only high-loaded (seeden). Andersrum stress Downloader range, contribute however even with its Upload range. By the following (only very theoretical) example is the effect of different quantities of pure offerers (Seeder) and Downloadern (Leecher) to be represented:

• A Upload range of 30 kilobytes per second has 5 complete Downloads, each of the connections on average: 5 30 = 150 KByte/s
• A Upload range of 30 KByte/s has 10 incomplete Downloads, each of the connections on average: 10 30 = 300 kbyte/s

The entire range in the network amounts to thus 150 KByte/s plus 300 KByte/s, entirely thus 450 KByte/s. 10 user at the same time downloads there, divides this available range on in on the average 45 KByte/s.

In the reality such is however usually reached a value on large, public Trackern only with popular Torrents, since also range is lost through waiting periods, allocations, different accessibilities etc. In addition in practice also different connection speeds and priorities are responsible for a more or less fast Runterladen.

On anti- Leech Trackern (explanation see below) such and still substantially higher Downloadraten is however very often to be found. Here also fast connections can be used as for instance DSL 6000 with Download speeds beyond the 500 KByte/s optimally.

Folder and applications

The BitTorrent Client eXeem distributed also the.torrent files and can do thereby without tracker. This program received bad criticisms however by the installation from Adware into the software (similar the program Kazaa).

Modern BitTorrent Clients can do without tracker and work thus decentralized ("„trackerless"”). However they use still different minutes, so that communication between different Clients on DHT basis is not always possible. Among themselves compatibly at present Azureus are and as well as Bitcomet and the Classic Client. The developers work however strengthened on it compatibility to manufacture.

Talk has belonged beside Ubuntu to the first Linux distributions, also with BitTorrent the CD-ROM of the distribution distributed and also Blizzard brought the World OF Warcraft beta and brings now, like ID software it already longer tried, the larger Patches for the final version by BitTorrent under the people. In the meantime all more well-known Linuxdistributionen and FreeBSD over BitTorrent are available. Also outside of the software range there are concrete applications: The British BBC undertakes at present pilot attempts, in order to make current transmissions and documentations available immediately after the radiant emittance on-line over BitTorrent.

Also various BitTorrent applications for the decentralized, anonymous and coded communications network work I2P exist.

Articles in category "BitTorrent"

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