THE BIT TORRENT PROTOCOL

Peer-to-Peer Networks

FILE TRANSFER PROTOCOL (FTP)

• Client-Server Model• Central server store the files • Large traffic to the server will lead to

download failure.• Shortcomings of FTP makes people to think over traditional FTP.

WHAT IS P2P NETWORK ?•Network built and sustained by the resources of each participant.

•Peers act as both client and server.

•Centralized/decentralized models.

TYPES OF P2P PROTOCOLS

• Napster• Gnutella (Bearshare, Limewire)• Kademlia (Overnet, eDonkey)• Fasttrack (Kazaa)• Bit torrent

BITTORRENT PROTOCOL

• Created by Bram Cohen• P2P(Peer To Peer) file transfer

protocol• Transfer of large files• Files are shared by many users• Active participation of all users• Huge success in file sharing domain since 2003

BITTORRENT NETWORK

TERMINOLOGIES

TORRENT

This refers to the small metadata file you

receive from the web server (the one that ends in .torrent)

Metadata here means that the file contains information about the data you want to

download, not the data itself.

TORRENT

• info: a dictionary that describes the file(s) of the torrent.

• announce: contains the URL of the “tracker”.• creation date• Comments from the author (optional)• created by (optional)• piece length: number of bytes in each piece

(integer).• pieces: string consisting of the concatenation of all

20-byte SHA1 hash values, one per piece.• private: (optional) is a field where the client requests

to avoid publicising it’s request.

WHAT DOES IT CONTAIN???

SEEDERS, LEECHERS & PEERS

• A peer is another computer on the internet that you connect to and transfer data.

• They are similar to peers in that they won’t have the complete file. But the main difference between the two is that a leech will not upload once the file is downloaded.

• A computer that has a complete copy of a certain torrent. Once a client downloads a file completely, he can continue to upload the file which is called as seeding..

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.

SWARM

The group of machines that are collectively connected for a

particular file.

VIRTUAL SEEDER

HOW DOES THE FILE DOWNLOAD HAPPEN?

1. Download the torrent file

2. Contact the tracker

3. Tracker response

4. Peer connection

5. Peer 'A' downloads a piece from the network

6. Piece exchange starts

7. Peers periodically the contact tracker

Visualization of the working ofBitTorrent

Visualization

Download files using BitTorrent

• First download a Torrent client to do us the job of downloading the files

• Then, go to a good Torrent search engine• Download the file with '.torrent' extension• Open it in your client• If the download starts with the progress

bar moving, take a deep breath!

BitTorrent Clients

• Deluge• Transmission• Ktorrent• Vuze• qBittorrent • Bittorrent • Bitcomet• µtorrent

Torrent search sites

• torrentz.com• piratebay.org• mininova.com• isohunt.com• extratorrent.com• kickass.to

BITTORRENT AND THE LAW

• The BITTORENT protocol (the technology)- No laws against file-sharing standards

• The BITTORENT client program- Similarly, the client software does not do anything

illegal

• *.TORRENT meta-files/trackers- A grey area

• Content files - It is illegal to download/upload copyright material.

Thanks for hearing me patiently!

QUESTIONS?