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Bittorrent
 

Bittorrent

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    Bittorrent Bittorrent Presentation Transcript

    • Bit torrent
      • 09BCE009:UTSAV DHOLAKIA
      • 09BCE010:VATSAL GAJERA
    • Flow of presentation
      • Introduction
      • Origin!
      • Why to use?
      • Terminology
      • Creating and downloading torrent
      • Security issues
      • Facts
    • Introduction
      • Bit torrent is a peer-2-peer file sharing protocol
      • One of the most common protocols for transferring large files and accounts
      • Bit torrent maximizes transfer speeds by breaking down a large file into numerous small pieces and allows a recipient to download each tiny piece form a different clients.
      • The only objective of bit torrent is to quickly give a copy of a single large file to a set of clients.
    • Origin!
      • Bit torrent is creation of an American programmer Brahm Cohen
      • Cohen revealed his idea at the first CODECON conference
      • Cohen wrote the bit torrent client implementation in python and several other programs have since implemented the protocol
      • Bit torrent is designed in April 2001 by Brahm Cohen and then maintained by Cohen ’ s company BitTorrent Inc.
    • Why Bit Torrent?????
    • Traditional client-server downloading
      • Millions want to download same popular huge files (for free)
        • Media
        • Softwares
      • You open a web-page and click a link to download a file to your computer
      • The web-browser software on your computer tells the server to transfer copy of the file to your computer
      • The transfer is handled by protocol such as FTP or HTTP
    • Host Router Source OVERLOAD
    • Disadvantages of client-server method
      • Client-server model fails if
          • Single server fails
          • Can ’ t afford to deploy enough servers
    • The Bit torrent(P2P) method
      • Bit torrent is a peer-2-peer file sharing protocol allowing users to distribute large amounts of data without putting the level of strain on their computers that would be needed for standard internet hosting
      • Peer-2-peer file sharing is different from traditional file downloading. In peer-2-peer sharing you use a software program rather then your web browser to locate computers that have the file you want. Because there are ordinary computers like yours as opposed to servers that are called peers.
    • P2P Protocols
    • Advantages of P2P method
      • No central point of failure
        • Eg. the internet & the web do not have a central point of failure.
        • Most internet & web services use the client-server model (e.g. HTTP) so a specific service does have a central point of failure
      • Scalability
        • Since every peer is alike, it is possible to add more peers to the system and scale to larger networks
    • Disadvantages of P2P Computing
      • Decentralized co-ordination
      • All nodes created are not equal
    • Terminology
      • Peers/ Leechers: A node or computer that does not have the complete file.
      • Seed or seeder: A computer with a complete copy of a Bit Torrent file.
      • Swarm: A group of computers simultaneously sending (uploading) or receiving (downloading) the same file.
      • .torrent: A pointer that directs your computer to the file you want to download.
      • Tracker: A server that manages the Bit Torrent file transfer process.
      • Share ratio: This is the ratio of the amount of data user has uploaded divided by the amount of data downloaded(UL/DL)
      • Index: An index is , as the name implies , searchable list of .torrent files hosted on websites.
    • Peer exchange different pieces of the file with one another until they assemble whole Machine with complete copy(the seed) can distribute incomplete pieces to multiple peers As soon as the user has a piece of the file on his machine he can become a source of that piece to other peers helping speed download All peers act as a source
    • Creating & Publishing Torrent
      • Peers that provide a complete file are called seeders, and the peer providing the initial copy is called the initial seeder.
      • The peer distributing a data file treats the file as a number of identically sized pieces, usually with byte sizes of a power of 2, and typically between 32 kB and 16 MB each.
      • Torrent File:
          • A bencoded metadata file consisting info about one or more files:
            • Name/size/date for each file
            • # no. of pieces of each files
            • SHA1 hash of each file
            • Trackers for the torrent
      • Torrent files are typically published on websites or elsewhere, and registered with at least one tracker. The tracker maintains lists of the clients currently participating in the torrent.
    • Creating & Publishing Torrent
      • Alternatively, in a trackerless system (decentralized tracking) every peer acts as a tracker. Azureus was the first BitTorrent client to implement such a system through the distributed hash table (DHT) method
      • After the DHT was adopted, a "private" flag — analogous to the broadcast flag  — was unofficially introduced, telling clients to restrict the use of decentralized tracking regardless of the user's desires.
      • The purpose of the flag is to prevent torrents from being shared with clients that do not have access to the tracker.
    • Downloading torrent files
      • Clients incorporate mechanisms to optimize their download and upload rates; for example they download pieces in a random order to increase the opportunity to exchange data, which is only possible if two peers have different pieces of the file.
      • Clients will decide from certain schemes that to which node ’ s request is to be satisfied. The schemes may be anyone from the following:
          • A tit for tat scheme
          • Optimistic unchocking
      • “ Seeder promotion problem ”
          • This occurs on a huge scale; measurements have shown that 38% of all new torrents become unavailable within the first month
      • BitTorrent does not offer its users anonymity. It is possible to obtain the IP addresses of all current and possibly previous participants in a swarm from the tracker
    • Technologies built on BitTorrent(Security Issues)
      • Distributed Trackers:
          • On May 2, 2005, Azureus 2.3.0.0 (now known as Vuze ) was released,introducing support for "trackerless" torrents through a system called the "distributed database." This system is a DHT implementation which allows the client to use torrents that do not have a working BitTorrent tracker . The following month, BitTorrent, Inc. released version 4.2.0 of the Mainline BitTorrent client, which supported an alternative DHT implementation (popularly known as "Mainline DHT") that is incompatible with that of Azureus.
          • Most BitTorrent clients also use Peer exchange (PEX) to gather peers in addition to trackers and DHT . Peer exchange checks with known peers to see if they know of any other peers.
    • Technologies built on BitTorrent(Security Issues)
        • Web Seeding:
            • Web seeding was implemented in 2006 as the ability of the bit torrent clients to download from HTTP sources in addition to swarm
            • This first specification requires running a web service that serves content by info-hash and piece number, rather than filename
      • 3. Throttling & Encryption:
            • Some ISP have chosen to reduce the amount of bandwidth given to bit torrent users and thus it reduces the traffic on the net.
            • So encryption technique called
              • 1.Protocol Header Encrypt(PHE)
              • 2.Message Stream Encryption/Protocol Encryption(MSE/PE)
              • are employed in the bit torrent downloads.
          • This encryption techniques have banned ISPs from viewing or reducing traffic when it is using bit torrent, it will not allow to distinguish it from other traffic.
    • Technologies built on BitTorrent(Security Issues)
        • Multitracker Systems:
          • Torrents with multiple trackers decrease download time but it has following consequences:
            • Poorly implemented clients may contact to several trackers, increasing traffic overhead on the network
            • Torrents from closed trackers may be downloaded by unauthorized users as they can contact multiple trackers
        • Legal Issues:
          • There has been several controversies about using bit torrent as it is usually seen that it distributes illegal and pirated softwares, games, media files, and encourage malware to be spread
          • Various countries have banned the use of bit torrent and many courts are filled up with the cases against bit torrent from different companies
    • Some FACTS
      • Bit torrent is responsible for roughly 27-55% of all internet traffic and 45-78% of P2P traffic
      • As of 2011 bit torrent has more than 100 million users and grater share of bandwidth than Netflix and Hulu combined
      • THE PIRATE BAY:
        • Who in september 2008 had 69,12,029 visits and 21,40,325 unique visitors making it 109th most popular website
      • Another popular torrent tracker isoHunt claims to have 9857 TB of data
    • References
      • http://www.bittorrent.com
      • http://www.wikipedia.org/bittorrent
      • http://computer.howstuffworks.com/bittorrent.htm
      • Thank you