BitTorrent – A revolution
in P2P networking
Mihir Jyoti Chakrabarti, Arijit Roy, Anirban
Sen
27 11 06
Swami Vivekananda Institute of Science and
Technology
Introduction
WHAT IS P2P NETWORKING?
2
Client/Server Architecture
What is it?
Client sends request, server provides the client with
data.
Server is the only data source.
3
Client/Server Architecture4
Problems
Scalability: how many users can a server support?
What happens when user traffic overload servers?
Limited resources (bandwidth, CPU, storage)
Reliability: if number of servers is small, what happens
when they break, fail, get disconnected, are
mismanaged by humans?
Efficiency: if your users are spread across the entire
globe, how do you make sure you answer their
requests quickly?
The Alternative: Peer-to-Peer
A simple idea
Provides as well as consumes network services.
A cooperative model: clients = peers = servers
5
A
B E
DC
Peer to Peer6
The benefits
Scalability: Number of “servers” grows with users
BYOR: bring your own resources (storage, CPU, B/W)
Reliability: load spread across many peers
Probability of them all failing is very low…
Efficiency: peers are distributed
Peers can try and get service from nearby peers
Types of P2P programs7
Centralized
In a centralized system a server maintains directories
of what is stored in each peer computer. The central
server directs the connections between peers.
Example Napster , Maze etc
Types of P2P programs8
De-Centralized
With a decentralized program each peer connect
directly to other peers without being directed by a
server. This connection is repeated making the
resulting network large.
Example: Gnutella
What is BitTorrent9
Programmer Bram Cohen designed the protocol in
April 2001 and released its first implementation of
the BitTorrent client on 2 July 2001.
Protocol for the practice of peer-to-peer file sharing
Designed for fast, efficient content distribution
Ideal for large files, e.g. movies, DVDs, ISOs, etc.
Not a full fledged P2P system
Does not support searching for files
Important Terminology 10
.torrent – Metadata file containing information(size,
about) about file to be shared via BitTorrent.
Share Ratio – The ratio of the amount of data you've
uploaded to the amount of data you've downloaded.
Peer – One instance of a BitTorrent client running on a
computer connected to the Internet to which other clients
connect and transfer data.
Seeder – A peer who has a complete copy of the torrent
and offers it for upload.
Important Terminology 11
Leech – Usually a peer who has a negative effect on
the swarm by having a very poor share ratio - in other
words, downloading much more than they upload.
Swarm – Together, all peers (including seeders) sharing
a torrent. For example, six ordinary peers and
two seeders make a swarm of eight.
Tracker – A tracker is a server that keeps track of which
seeds and peers are in the swarm. The tracker is not
directly involved in the data transfer and does not have a
copy of the file.
Piece – This refers to the torrent files being divided up
into equal specific sized pieces (i.e. 512Kb, 1Mb).
Sharing Pieces12
Initial Seeder
1 2 3 4 5 6 7 8
Peer
1 2 3
Peer
54 76 8 1 2 3 54 76 8
Seeder Seeder
Working of BitTorrent13
Tracker
Swarm
Leechers
Seeder
The Beauty of BitTorrent14
More seeders = more availability of the full file
Great for content distribution
More peers = more replicas of pieces
More replicas = faster downloads
Multiple sources for each piece
Screenshot of a BitTorrent Client 15
History of BitTorrent16
Bram Cohen (born October 12, 1975) created the
first file sharing program to use the protocol, also
known as BitTorrent.
Prior to version 6.0, BitTorrent was written in Python,
and was free software. Very early versions released
prior to December 30, 2001 were released into
the public domain without a license. Versions up to and
including 3.4.2 were distributed under the MIT license.
Since version 6.0, the BitTorrent client has been a
rebranded version of µTorrent. As a result, it is no
longer open source.
BitTorrent Revolution17
BitTorrent Revolution18
19
WHAT IS LEGAL AND
ILLEGAL?
Illegal Events20
Finland: Finreactor
Hong Kong: Individual actions
Singapore: Odex actions against users
Slovenia: Suprnova
Sweden: Pirate Bay
TorrentSpy
Conclusion21
One thing for sure, torrent is not equal to piracy.
The torrent protocol is just a transmission mean for users to download files more easily.
It is the content (not the protocol) that makes the act illegal. When it comes to downloading through the torrent protocol, there’s no real way to stay completely safe.
However, it remains one of the most effective peer-to-peer protocols in the world. If you’re worried that you may be downloading something that’s against the laws in your country, follow your moralistic instinct.
Reference22
http://en.wikipedia.org
http://www.google.co.in
http://www.krazytech.com
http://www.slideshare.net
http://blog.seattlepi.com/timothymccormack/2013/0
7
http://historycomputer.com/Internet/Conquering/Bit
Torrent.html
http://www.youtube.com
http://www.bittorrent.com
Clear Your Doubts23