BT Terminology

A list of commonly used terms in relation to the BitTorrent protocol.

Terms

Announce: The process in which a client requests a tracker to add it to a swarm.

Client: A program that manages torrent downloads and uploads using the BitTorrent protocol.

Distributed Hash Tables (DHT): A trackerless system used by many BitTorrent clients to gather more peers than are available on a single tracker. The DHT network may not be used in the BakaBT community.

Hash: A string of alphanumeric characters in the .torrent file that the client uses to verify the data that is being transferred.

Index: A list of .torrent files managed by a website and available for searches.

Interested: Term used in the protocol specification. It refers to the state of a downloader with respect to a connection. A downloader is marked as interested if the other end of the link has any pieces that the client wants, otherwise the connection is marked as not interested.

Leech: A peer that is currently downloading a file from other peers. Leech can also have a negative connotation referencing a peer that does not seed after downloading has completed.

Optimistic unchoking: Periodically, the client shakes up the list of uploaders and tries sending on different connections that were previously choked, and choking the connections it was just using.

Peer-to-Peer (P2P): The technology used for file sharing among computer users over the internet.

Peer: An instance of a BitTorrent client running on a computer on the Internet to which other clients connect and transfer data; a participant in a swarm. Generally a peer does not have the complete file, otherwise it would be called a seed. Some people also refer to peers as leeches, to distinguish them from those generous folks who have completed their download and continue to leave the client running and act as a seed.

Peer Exchange (PEX): A trackerless system used by many BitTorrent clients to gather more peers than are available on a single tracker. Peer Exchange may not be used in the BakaBT community.

Piece: This refers to the torrented files being divided up into equal specific sized pieces. The pieces are distributed in a random fashion among peers in order to optimize trading efficiency. Pieces can also be downloaded sequentially, but this is not recommended as it may slow the download process.

Reseed: When there are zero seeds for a given torrent (and not enough peers to have a distributed copy), then eventually all the peers will get stuck with an incomplete file, since no one in the swarm has the missing pieces. When this happens, someone with a complete file (a seed) must connect to the swarm so that those missing pieces can be transferred. Usually a request for a reseed comes with an implicit promise that the requester will leave his or her client open for some time period after finishing.

Scrape: A request from a client to a tracker in order to gather information about a certain torrent (number of peers, peer share ratios, etc.)

Seed: A peer that has finished downloading a file and is currently uploading pieces to other peers.

Share Ratio: A number determined by dividing the total uploaded data by the total downloaded data in a torrent. BakaBT encourages users to have a share ratio of greater than one.

Snatched: The number of times the .torrent file was downloaded. This does not mean the number of times the torrent has been completed.

Snubbed: If the client has not received anything after a certain period (default: 60 seconds), it marks a connection as snubbed, in that the peer on the other end has chosen not to send. See the definition of choked for reasons why an uploader might mark a connection as choked.

Super Seeding (Initial Seeding in uTorrent): A method in which a client reduces the amount of data that needs to be sent when seeding a new torrent or re-seeding a torrent. This method supposedly improves the distribution of data. This method is useful for people who pay their ISPs depending on how much data he/she transfers.

Swarm: Together, all peers (including seeders) sharing a torrent are called a swarm.

Torrent: The torrent file contains metadata about all the files it makes downloadable (Metadata means that the file contains information about the data you want to download, not the data itself), including their names and sizes and checksums of all pieces in the torrent. It also contains the address of a tracker that coordinates communication between the peers in the swarm.

Tracker: 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.