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See Shared resource for the conventional meaning of file sharing

File sharing usually follows the peer-to-peer (P2P) model, where the files are stored on and served by personal computers of the users. Most people who engage in file sharing on the Internet both provide (upload) files and receive files (download).

P2P file sharing is distinct from file trading in that downloading files from a P2P network does not require uploading, although some networks either provide incentives for uploading such as credits or forcing the sharing of files being currently downloaded.

First P2P-generation: Server-client

The first generation of peer-to-peer file sharing networks had a centralized file list. In the centralized peer-to-peer model, a user would send a search to the centralized server of what they were looking for. The server then sends back a list of peers that have the data and facilitates the connection and download.

The first file-sharing programs marked themselves by inquiries to a server, either the data to the download held ready or in appropriate different Peers and so-called Nodes further-obtained, so that one could download there. Two examples were Napster (today using a pay system) and eDonkey2000 in the server version (today, likewise with Overnet and KAD - network decentralized). Another notable instance of peer to peer file sharing, which still has a free version, is Limewire.

Web-based sharing

Webhosting is also used for file-sharing, since it makes it possible to exchange privately. In small communities popular files can be distributed very quickly and efficiently. Web hosters are independent of each other; therefore contents are not distributed further. Other terms for this are one-click hosting and web-based sharing.

File Sharing On The Social Graph

Recently, Facebook opened up its API to 3rd party developers that has allowed for a new type of file-sharing service to emerge. Box.net and FreeDrive.com [2] are two examples of companies that have specific Facebook Applications that allow file sharing to be easily accomplished between friends.

Server-client-protocols

Audiogalaxy - Service ended in the middle of 2002.
Direct Connect
Napster - Closed in its original form in July 2001, since changed to a fee-based service.
Scour Exchange - The second exchange network after Napster. No longer exists.
Soulseek - Still popular today despite being relatively old, with more than 120,000 users online at any time.
TinyP2P - 15 lines Python - SOURCE code
WinMX - The original Frontcode servers were switched off in September 2005, but alternate servers can be used by installing a Software Patch.

Second P2P-Generation: Decentralization

After Napster encountered legal troubles, Justin Frankel of Nullsoft set out to create a network without a central index server, and Gnutella was the result. Unfortunately, the Gnutella model of all nodes being equal quickly died from bottlenecks as the network grew from incoming Napster refugees. FastTrack solved this problem by having some nodes be 'more equal than others'.

By electing some higher-capacity nodes to be indexing nodes, with lower capacity nodes branching off from them, FastTrack allowed for a network that could scale to a much larger size. Gnutella quickly adopted this model, and most current peer-to-peer networks implement this design, as it allows for large and efficient networks without central servers.

Also included in the second generation are distributed hash tables (DHTs), which help solve the scalability problem by electing various nodes to index certain hashes (which are used to identify files), allowing for fast and efficient searching for any instances of a file on the network. This is not without drawbacks; perhaps most significantly, DHTs do not directly support keyword searching (as opposed to exact-match searching).

The best examples are Gnutella, Kazaa or eMule with Kademlia, whereby Kazaa has still a central server for logging in. eDonkey2000/Overnet, Gnutella, FastTrack and Ares Galaxy have summed up approx. 10.3 million users (as of April 2006, according to slyck.com). This number does not necessarily correspond to the actual number of persons who use these networks; it must be assumed that some use multiple clients for different networks.

Multi-Network-Clients

See Multi-network applications

Further networks or clients

See other networks

Third P2P-Generation: indirect and encrypted

The third generation of peer-to-peer networks are those that have anonymity features built in. Examples of anonymous networks are ANts P2P, RShare, Freenet, I2P, GNUnet and Entropy.

A degree of anonymity is realized by routing traffic through other users' clients, which have the function of network nodes. This makes it harder for someone to identify who is downloading or who is offering files. Most of these programs also have strong encryption to resist traffic sniffing.

Friend-to-friend networks only allow already-known users (also known as "friends") to connect to the user's computer, then each node can forward requests and files anonymously between its own "friends" nodes.

Third-generation networks have not reached mass usage for file sharing because most current implementations incur too much overhead in their anonymity features, making them slow or hard to use. However, in countries where very fast fiber-to-the-home Internet access is commonplace, such as Japan, a number of anonymous file-sharing clients have already reached high popularity.

An example might be: Petra gives a file to Oliver, then Oliver gives the file to Anna. Petra and Anna thus never become acquainted and thus are protected. Often used virtual IP addresses obfuscate the user's network location because Petra only knows the virtual IP of Anna. Although real IP's are always necessary to establish a connection between Petra and Oliver, nobody knows if Anna really requested and Petra really send the file or if they just forward it (As long as they won't tell anyone their virtual IP's!). Additionally all transfers are encrypted, so that even the network administrators cannot see what was sent to whom. Example software includes WASTE, JetiANts, Tor and I2P. These clients differ greatly in their goals and implementation. WASTE is designed only for small groups and may therefore be considered Darknet; ANts and I2P are public Peer-to-Peer systems, with anonymization provided exclusively by routing reach.

Ants network

Mute network

MUTE
Kommute - KDE

I2P network

I2P
I2Phex - Gnutella over I2P
iMule - eDonkey (Kademlia) over I2P
Azureus - has I2P plugin

Retroshare-Network (F2F Instant Messenger)

Retroshare Instant Messenger - Retroshare Chat Messenger for privacy of filesharing

other networks or clients

The fourth P2P-Generation: Streams over P2P

Apart from the traditional file sharing there are services that send streams instead of files over a P2P network. Thus one can hear radio and watch television without any server involved -- the streaming media is distributed over a P2P network. It is important that instead of a treelike network structure, a swarming technology known from BitTorrent is used. Best examples are Peercast, Miro, Cybersky and demo TV.

General

Tree structure

Swarm structure such as BitTorrent

Economic impact

Since illegally downloading files has become more common, there has been much controversy about whether infringement of copyrighted music has either hurt or helped CD sales.

Some economic studies have found that file sharing has a negative impact on record sales. For example, three papers published in the April 2006 issue of the Journal of Law and Economics (Liebowitz, Rob and Waldfogel, Zentner) all found harm from filesharing. Alejandro Zentner notes in another paper published in 2005 (Topics in Economic Analysis & Policy), that music sales have globally dropped from approximately $38 billion in 1999 to $32 billion in 2003, and that this downward trend coincides with the advent of Napster in June of 1999. Finally, using aggregate data Stan J. Liebowitz argues in a series of papers (2005, 2006) that file sharing had a significant negative impact on record sales.

However, the most widely cited paper concludes that file sharing has no negative effect on CD sales. This paper by Olberholzer-Gee and Strumpf,^[1] was published in the February 2007 issue of the Journal of Political Economy, and is the only paper which analyzes actual downloads on file sharing networks. As staff writer John Borland of CNET News.com reports, “even high levels of file-swapping seemed to translate into an effect on album sales that was ‘statistically indistinguishable from zero,’ they [the researchers] wrote.”^[2] From data gathered from the many weeks of tracking downloading on OpenNap servers they found that most users logged on very rarely and when they did log on they only downloaded a little more than one CD’s worth of songs. To show how these downloads affected album sales they tracked sales and downloads of 500 random albums of varying genres and after doing so found that illegal downloads would only be a small force in the decrease in album sales, possibly even slightly improving album sales of the top albums in stores at the time.^[2]

Some researchers believe that massive copying has been occurring ever since the invention of tape cassettes and the increased economic impact of simpler access to copying provided by computer networks does not seem to have been large.^{[citation needed]}.

According to an article published by the Almighty Institute of Music Retail, an estimation of 900 independent record stores have closed since 2003, leaving 2,700 nationwide. Carolyn Draving, the owner of Trac Records is being closed after 32 years and she believes the downfall is a direct result of the illegal internet. She states that she lost many long-time consumers to the internet and knows for certain that a few stopped coming in because they just downloaded instead. Another owner, Warren Greene of Spinsters Records claims that nobody buys CD’s anymore and that most of his customers have turned to the internet in order to obtain their music.

In order to keep these smaller record stores alive, owners are having to find alternative means to stay afloat. Greene has saved his store from going under “...by finding a new product to sell: T-shirts emblazoned with digital images.”^[3]He purchased a digital garment printing machine that lets him print any digital photo a customer wants onto a T-shirt. The shirts sell for $20 to $25, and are creating a higher profit margin than the sale of CD’s.

An article posted in the Wall Street Journal have found that CD sales have dropped 20% since last year, which they say is the latest sign of the shift in the way people acquire their music. While the music industry, along with other types of media such as film and TV are having a difficult time adapting to the digital age, BigChampagne LCC has reported that around one billion songs a month are being traded on illegal file-sharing networks. As a result of this decline in CD sales, a significant amount of record stores are going out of business and “...making it harder for consumers to find and purchase older titles in stores.”^[4]

Legal and copyright issues

File sharing grew in popularity with the proliferation of high-speed Internet connections, and the relatively small file size and high-quality MP3 audio format. Although file sharing is a legal technology with legal uses, many users use it to download and upload copyrighted materials without permission, which can be copyright infringement if done without authorization for improper purposes. Despite the existence of various international treaties, there are still sufficient variations between countries to cause significant difficulties in the protection of copyright. This has led to attacks against file sharing in general from many copyright owners and litigation by industry bodies against private individual sharers. The legal issues surrounding file sharing have been the subject of debate and conferences, especially among lawyers in the entertainment industries. [3] The challenges facing copyright holders in the face of file-sharing systems are quite novel historically and have highlighted many new challenges in both theory and practice:

Ambiguities in the interpretation of copyright law
The new challenges posed by international communications and varying legislations
Mass litigation and the development of processes for evidence and discovery
Rapidly developing new technologies and uses
Low barriers to entry by would-be sharers and the development of a mass usage of the technologies
File-sharing approaches developed in response to litigation against sharers, which obfuscate or hide the fact that sharing is happening, or the identities of those involved. For example: encryption and darknets.
The transfer of segmented files that; arguably, by themselves do not constitute a copyright issue.

Further challenges have arisen because of the need to balance self-protection against fair use. A perceived overbalance towards protection (in the form of media that cannot be backed up, cannot be played on multiple systems by the owner, or contains rootkits^[5] or irksome security systems inserted by manufacturers) has led to a backlash against protection systems in some quarters. For example, the first crack of AACS was inspired by a perceived unfair restriction on owner usage.^[6]

Public perception

According to a poll, 75% of young voters in Sweden (18-20) support file sharing when presented with the statement:

I think it is OK to download files from the Net, even if it is illegal.

Of the respondents, 38% said they "adamantly agreed" while 39% said they "partly agreed".^[7]

Attacks on peer-to-peer networks

Many peer-to-peer networks are under constant attack by people with a variety of motives.

Examples include:

Poisoning attacks (e.g. providing files whose contents are different from the description, aka "spoofing")
Polluting attacks (e.g. inserting "bad" chunks/packets into an otherwise valid file on the network)
Defection attacks (users or software that make use of the network without contributing resources to it)
Insertion of viruses to carried data (e.g. downloaded or carried files may be infected with viruses or other malware)
Malware in the peer-to-peer network software itself (e.g. distributed software may contain spyware)
Denial of service attacks (attacks that may make the network run very slowly or break completely)
Filtering (network operators may attempt to prevent peer-to-peer network data from being carried)
Identity attacks (e.g. tracking down the users of the network and harassing or legally attacking them)
Spamming (e.g. sending unsolicited information across the network--not necessarily as a denial of service attack)

Risks

Some file-sharing software comes bundled with malware such as spyware, viruses, adware, or otherwise privacy-invasive software. Sometimes this unwanted software remains installed on the system even if the original file-sharing software is removed, and can be very difficult to eliminate. In many cases such malware can interfere with the correct operation of web browsers, anti-virus software, anti-spyware and software firewalls; can cause degraded performance on affected systems; and in some cases may secretly compromise a user's privacy or security. Malware is typically bundled with proprietary software, and not those in open source. In most cases it is possible to remove adware and spyware by running spyware removal programs. Such programs can often remove malware without influencing the functionality of the file-sharing software.

Some are also concerned about the use of file-sharing systems to distribute adult pornography to children, child pornography to anyone, inflammatory literature, and illegal or "unpopular" material. Novice users may find it difficult to obtain information about which networks, if any, are "safe" for them to use. With experience, users can reduce their exposure to offensive material by structuring their searches carefully (for example, a search limited to audio file types avoids exposure to video and image files).^[8]

References

^ The Literature
^ ^a ^b By “John Borland”, See [1].
^ By “John Wilen”, See Almighty Institute of Music Retail.
^ By “Ethan Smith”, See Wallstreet Journal Website.
^ See 2005 Sony BMG CD copy protection scandal.
^ By "Muslix64", written on doom9's forum. See original post and the ensuing AACS encryption key controversy.
^ The Local - Young voters back file sharing
^ Morris, Alan (2003-08-22). "Testimony of Mr. Alan Morris about Pornography, Technology and Process: Problems and Solutions on Peer-to-Peer Networks". United States Senate, Committee on the Judiciary, Washington, DC. Retrieved 2006-11-20.

External links

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[1] The Literature

[”Borland”-2] By “John Borland”, See [1].

[Wilen-3] By “John Wilen”, See Almighty Institute of Music Retail.

[4] By “Ethan Smith”, See Wallstreet Journal Website.

[5] See 2005 Sony BMG CD copy protection scandal.

[6] By "Muslix64", written on doom9's forum. See original post and the ensuing AACS encryption key controversy.

[7] The Local - Young voters back file sharing

[8] Morris, Alan (2003-08-22). "Testimony of Mr. Alan Morris about Pornography, Technology and Process: Problems and Solutions on Peer-to-Peer Networks". United States Senate, Committee on the Judiciary, Washington, DC. Retrieved 2006-11-20.

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@@ Line 5: / Line 5: @@
 P2P file sharing is distinct from file trading in that downloading files from a P2P network does not require uploading, although some networks either provide incentives for uploading such as credits or forcing the sharing of files being currently downloaded.
-== First P2P-generation yo yo yo (Y) : Server-client ==
+== First P2P-generation: Server-client ==
 The first generation of peer-to-peer file sharing networks had a centralized file list. In the centralized peer-to-peer model, a user would send a search to the centralized server of what they were looking for. The server then sends back a list of peers that have the data and facilitates the connection and download.
 The first file-sharing programs marked themselves by inquiries to a server, either the data to the download held ready or in appropriate different [[Peer-to-peer|Peer]]s and so-called [[Node (networking)|Node]]s further-obtained, so that one could download there. Two examples were [[Napster]] (today using a pay system) and [[eDonkey2000]] in the server version (today, likewise with [[Overnet]] and [[Kademlia|KAD]] - network decentralized). Another notable instance of peer to peer file sharing, which still has a free version, is [[Limewire]].
-===Web-based sharing ===  yo yo yo :)
+===Web-based sharing ===
 [[Webhosting]] is also used for file-sharing, since it makes it possible to exchange privately. In small communities popular files can be distributed very quickly and efficiently. Web hosters are independent of each other; therefore contents are not distributed further. Other terms for this are one-click hosting and web-based sharing.