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