BitTorrent tracker
From Wikipedia, the free encyclopedia
A BitTorrent tracker is a server which assists in the communication between peers using the BitTorrent protocol. It is also, in the absence of extensions to the original protocol, the only major critical point, as clients are required to communicate with the tracker to initiate downloads. (Clients that have already begun downloading also communicate with the tracker periodically to negotiate with newer peers and provide statistics; however, after the initial reception of peer data, peer communication can continue without a tracker.)
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[edit] Trackers and Indexers
A tracker should be differentiated from a BitTorrent index by the fact that it does not necessarily list files that are being tracked. A BitTorrent index is a list of .torrent files (usually including descriptions and other information). Trackers merely coordinate communication between peers attempting to download the payload of the torrents.
Many BitTorrent websites act as both tracker and index. Sites such as these publicize the tracker's URL and allow users to upload torrents to the index with the tracker's URL embedded in them, providing all the features necessary to initiate a download.
[edit] Private Trackers
A private tracker is a tracker which restricts who can use it, often by requiring registration of a user account. Private trackers usually register how much the users upload and download and may enforce a minimum upload-to-download ratio. As a result their torrents usually offer better availability and speed compared to public trackers where leeching is more common. The concept was pioneered by the (now defunct) site TorrentBits on whose code many private trackers are now based.
[edit] Legal Issues
Many torrent trackers have been the target of cease and desist lawsuits from copyright bodies, despite the fact that they do not actually host any of the copyrighted data themselves. Some torrent tracking websites are operated in countries with copyright laws that differ from the country of origin of the copyrighted material.
In many countries, it is illegal to distribute copyrighted material without the permission of the copyright holder. Of course, there are many circumstances under which it is legal to distribute copyrighted material. For instance, copyright holders may choose to allow their content to be distributed for free, using licenses such as the Creative Commons family, or the GPL. There are also the fair use provisions of copyright law, which allow people to use copyrighted material for parody, criticism, review and other purposes. In addition, there are currently some experiments at legally selling content that is distributed over BitTorrent using a "secure" tracker system.
[edit] Improving tracker reliability
Trackers are the primary reason for a damaged BitTorrent 'swarm'. (Other reasons are mostly related to damaged or hacked clients uploading corrupt data.) The reliability of trackers has been improved through two main innovations in the BitTorrent protocol:
[edit] Multi-tracker torrents
Multi-tracker torrents feature multiple trackers in the one torrent. This way, should one tracker fail, the others can continue supporting file transfer.
[edit] 'Tracker-less' torrents
There are two incompatible 'trackerless' BitTorrent transfer (aka. decentralized tracking) methods: DHT-based implementations, and Azureus' 'Distributed Database'.
The term 'trackerless' is something of a misnomer, as decentralized or distributed tracking essentially treats every peer in the swarm as a tracker. The original BitTorrent client was the first to offer decentralized tracking through its DHT method. Later, Azureus, µTorrent, BitComet and KTorrent adopted this feature, although Azureus's method of implementation is incompatible with the DHT offered by all other supporting clients.
[edit] See also
- BitTorrent
- Bram Cohen
- BitTorrent client
- Distributed hash table
- UDP tracker
- BNBT - C++ port of the original BitTorrent tracker written in Python by Bram Cohen
- XBT Tracker - C++ BitTorrent tracker designed for performance (does not serve .torrent files or other web pages); requires MySQL
- URLGrab Tracker Index
| BitTorrent (category) | |
|---|---|
| Companies | BitTorrent, Inc. |
| Prominent individuals | |
| Technology | Tracker • Client • Super-seeding • Peer exchange • Broadcatching (BT RSS List) |
| Prominent clients (category) |
Official BitTorrent Client • ABC • Azureus • BitComet • BitTornado • KTorrent • Transmission • µTorrent • Halite
|
| Prominent sites (category) | LokiTorrent • Suprnova.org • The Pirate Bay • AnimeSuki • Demonoid • Mininova • isoHunt • TorrentSpy • Empornium • UKNova |
