1. BitTorrent
Presented By :Seminar Guide:
Ashish KumarMs. Preetha M Kurup
Roll no.: 17
Cs A

2. Contents:
Introduction
Working of BitTorrent
Terminology
Architecture of bitTorrent
Simple example
Conclusion
References

3. Introduction
BitTorrent is a peer to peer communication protocol for file sharing.
The data to be shared is divided into many equal sized portions called pieces.
Each piece is further sub-divided into equal-sized sub-pieces called blocks.
All clients interested in sharing the same data are grouped into a swarm.
It does not require a user to download a file completely from a single server.

4. Introduction
Instead a file can be downloaded from many such users who are indeed downloading the same file.
A user who has the complete file, called the seed will initiate the download by transferring pieces of file to the users.
Once a user has some considerable number of such pieces of a file then even he can start sharing them with other users who are yet to receive those pieces.
Pieces are not downloaded in sequential order.

5. Introduction
This concept enables a client not to depend on a server completely .
It also reduces the overall load on the server.

6. Terminology
Torrent : refers to the small metadata file you receive from the web server.
Peer : A peer is another computer on the internet that you connect to and transfer data.
Leech: peer thats downloading the file
Seed: A computer that has a complete copy of a certain torrent.
Swarm: The group of machines that are collectively connected for a particular file.

7. Terminology
Tracker : A server on the Internet that acts to coordinate the action of BitTorrent clients. The clients are in constant touch with this server to know about the peers in the swarm.
Share ratio : This is ratio of amount of a file downloaded to that of uploaded.
Choked: It is a state of an uploader where he does not want to send anything on his link. In such cases, the connection is said to be choked.

8. Swarm -snapshot

9. Working of BitTorrent
BitTorrent protocol shares data through what are known as torrents.
For a torrent to be alive or active it must have several key components to function.
These components include a tracker server, a .torrent file, a web server where the .torrent file is stored and a complete copy of the file being exchanged.
The first step in the BitTorrent exchange occurs when a peer downloads a .torrent file from a server.

10. Working of BitTorrent
The role of .torrent files is to provide the metadata that allows the protocol to function.
The .torrent files contains :

• The URL of the tracker
• 11. Pieces
• 12. Piece length
• 13. Name of the file
• 14. Length of the file