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P2P

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Peer-to-peer (or P2P) is a computer network model close to the client-server model but where each client is also a server. The peer-to-peer can be centralized (the connections pass through an intermediate central server) or decentralized (the connections are made directly). It can be used for peer-to-peer file sharing (allows Internet users to share files and download files from others), distributed computing (creating a distributed computing resource around the world to use computing power to perform calculations that are too complex to be performed in a laboratory) or for communication. Peer-to-peer systems allow multiple computers to communicate over a network, sharing objects, which are often files, but also streaming, distributed computing, a service like telephony IP, etc... The peculiarity of peer-to-peer architectures lies in the fact that the data can be transferred directly between two stations connected to the network without passing through a central server. It allows all computers to play the role of client and server directly.

P2P File Sharing

Peer-to-peer file sharing is a network that allows users to share files between multiple computers connected to each other over the Internet : each user can be a server and receiver of another user. They form “peers”. The essential technical advantage of the system over centralized loading is that the more content has applicants on a central server, the more it is congested. On the contrary, the more it has on a peer-to-peer network, the greater the download speed from all these combined partial sources. This technology is called Segmented file transfer, it is nicknamed swarming downloads.

Some examples of P2P file sharing

Peer-to-peer file sharing technology has evolved through several design stages from the early networks like Napster, which popularized the technology, to the later models like the BitTorrent protocol.


Napster

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The first software used on a large scale, called Napster is created in June 1999. Its first goal was only to easily exchange music with friends, but it quickly became dedicated to download MP3 format on the Internet using a centralized search engine to download files without going through this server. From the first week, 15,000 people downloaded the software, then 23 million in July 2000.


KaZaA

In 2001, while the first legal pressures weighed on Napster, the suspicious users retreated to KaZaA, a network of the company Sharman Networks, based on a decentralized peer-to-peer architecture (Internet users are connected directly to each other and no longer via centralized servers), they are therefore more immune to justice because the creator isn’t responsible for the activities of the users.


eDonkey

In a complementary time, in 2003 the family eDonkey2000 (and its evolutions : eMule, Overnet) surpasses KaZaA and takes over in the habits of the users. Thanks to peer-to-peer experience, programmers who use these systems develop the technique of file splitting (barely a download started), the recovered part is already available for uploading.


BitTorrent

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In spite of everything, the new generation is already ready for the classics like KaZaA, and even for the recent eDonkey clones. The generation of GrabIt and BitTorrent recently lowers the frequency of their competitors. We also see the emergence of peer-to-peer systems like ANts that operate on an anonymous mode. Concretely, the data travels from user to user in a totally encrypted way.

Limewire was a very popular music and media sharing tool that was similar to the platforms above. It was started in 2000 and was very popular in its time. It was one of the lading programs of its type but got shut down due to law suits from record companies.

Consequences

As P2P file sharing technologies are progressing, the music and video industries are falling down, losing billions of dollars because they can’t sell CDs and DVDs anymore. Indeed, "pirates" found a way to put videos online and enable millions of users to upload and watch these films freely (on streaming websites) : this tendency is called the online video piracy or digital theft. It is now so easy to find a film online for free that people think it can’t be wrong to do that. Indeed, it exists so many streaming websites, that Internet users can watch immediately and without transferring a full copy of any movie or show from the Internet to their hard drive.

Distributed computing

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Distributed or shared computing is the action of spreading a calculation or processing on several microprocessors and more generally any computer central processing unit. Distributed computing is often performed on specialized computing clusters, but can also be performed on individual multi-core computing stations. The distribution of a calculation is a field of research in the mathematical and computer sciences. It implies in particular the notion of parallel computation.

References

1. http://searchnetworking.techtarget.com/definition/peer-to-peer

2. https://en.m.wikipedia.org/wiki/Peer-to-peer_file_sharing

3. http://www.nytimes.com/2009/02/05/business/media/05piracy.html

4. http://whatis.techtarget.com/definition/distributed-computing

5. https://en.wikipedia.org/wiki/LimeWire