Bittorent Presentation

A SEMIMAR REPORT ON BITTORENT PROTOCOL

Outline 1 Introduction  2 Overview of BitTorrent  3 BitTorrent protocol 1.0  4 New features  5 References 

1 Introduction    

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30% of all Internet bandwidth was used by BitTorrent at the end of 2004. popular ways of sharing and downloading files. BitTorrent is used for legal distribution of files and to illegally share and download of copyrighted material. Due technology within the protocol large amounts of data can be distributed without the need of a high capacity server, and expensive bandwidth. Bittorent is decentralized.

2 Overview of BitTorrent  BitTorrent is

a file sharing protocol, implementing peer-to-peer technology.  A file is divided into smaller pieces.  A piece downloaded by a peer is then shared for uploading by that peer. 

COMPONENTS OF THE PROTOCOL 

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Metainfo file. Describes metadata about the sharing file(s), and the tracker, and has the file ending .torrent. Tracker. A central server keeping track of peers and seeds sharing and downloading the file(s). Peer. A user on the network downloading the file(s), and sharing the parts that have been successfully downloaded. Seed. A peer that has the complete file or files available for sharing. At least one seed is needed in the beginning for the sharing to be possible. Client. An application implementing the BitTorrent protocol.

BITTORENT WORKING

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 contact tracker.

3 BitTorrent protocol 1.0  designed

by Bram Cohen. 3.1 Metainfo file structure: .torrent file is bencoded.  Bencoding -way to organize data. Types supported : byte strings, integers, lists and dictionaries.  A metainfo file can be in one of two modes: Single-file mode and Multi-file mode. 

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Keys in the dictionary  length:

The length of the file in bytes  · name: The name of the file  · piece length: The piece length in bytes  · pieces: A 20 byte SHA1 hash file.  md5sum: 32 byte string file.  announce-list: list of tracker URL.  creation date  Comment  created by

3.2 Tracker protocol  implemented on

top of HTTP/HTTPS.  client sends a GET request to the tracker URL+CGI variables.  E.g.http://some.url.com /announce?var1=value1&var2=value2&var3=  tracker responds with a “text/plain” document, containing a bencoded dictionary.  client then sends rerequests, either on regular intervals, or when an event occurs, and the tracker responds.

4 New features 4.1 DHT (Distributed Hash Table)  Problems: centralized services,(query flooding broadcasts a message over whole network). Merits of DHT:  provides lookup service.  Any participating node can retrieve the value associated with given key easily.  Maintenance of mapping keys is distributed to nodes.  Highly scalable. 

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4.2 Multi trackers  To

avoid interruption when a tracker fails, multiple trackers is used.  [‘announce-list’] = [ [tracker1] , [backup1] , [backup2] ]  [ [tracker3,tracker2,tracker1] ] [‘announce-list’] = [ [tracker1,tracker2] , [backup1] ] 

4.3 Encryption  Due

to high BitTorrent traffic of 30% bandwidth, some ISPs block BT traffic.  encryption of BitTorrent traffic was implemented in some clients to fool the ISPs blocking system.  encrypting and recognition of BitTorrent traffic, takes up resources.  That’s why ISPs don’t implement this kind of blocking.  It is known as traffic shaping or bandwidth throttling. 

5 References

 http://www.cachelogic.com/research/2005_slide06 

http://www.bittorrent.com/protocol.html

  http://wiki.theory.org/BitTorrentSpecification   http://home.elp.rr.com/tur/multitracker-spec.txt 

 http://www.cs.rice.edu/Conferences/IPTPS02/174.  http://www.slyck.com/news.php?story=1083  

The Pirate Bay Raid 2004: MPAA pressured the U.S. and Swedish government to shut down The Pirate Bay  May 2006: Police in Sweden raided The Pirate Bay, shut down their website, & confiscated their servers  The Pirate Bay 

 BitTorrent search engine & tracker server  Launched in November 2003 by

Gottfrid Svartholm & Fredrik Neij

Down for 3 days  Publicity and +1.7 million more users 

The Pirate Bay Trial January 2008: Criminal & civil prosecution in Sweden for promoting the copyright infringement of others with torrents by the International Federation of the Phonographic Industry (IFPI).  Fredrik Neij, Gottfrid Svartholm, Peter Sunde, and Carl Lundström  Found guilty 

Sentenced to 1 year in prison Pay a fine of $3.5 million

SUBMITTED BY YOGENDRA KUMAR SAHU (0201IT071089) PRASHANT KUMAR (0201IT071049) IT V SEM JABALPUR ENGINEERING COLLEGE JABALPUR