How does P2P work?

Aram

May 15, 2012

¶ 1 Leave a comment on paragraph 1 0 Before exploring the social and economic ramifications of peer-to-peer file sharing, it would be helpful to review some of the key concepts and components of this platform. There is no single technology, protocol or architecture underpinning P2P, nor is there even a clear boundary separating P2P from other forms of online information-sharing. Though it typically gets represented as a kind of digital black market, a shady back alley where contraband and counterfeits flourish free from the prying eyes of the authorities, this representation is wrong on at least two important counts. First, P2P isn’t a “place” any more than email or instant messaging is a place. It is simply a collection of diverse and often competing technologies, any of which may enable two or more users (or “peers”) to share digital information, encoded in a file of any kind. Like email, this platform may be accessed via a web site or via a stand-alone application, yet it is independent of these avenues of entry. In the parlance of computer developers, these websites and applications are “front-ends,” and the P2P protocol or network in question is the “back-end.”

¶ 2 Leave a comment on paragraph 2 0 Second, there is nothing necessarily shady or illicit about the material being shared on these networks – at least, no more than is the case for any other communication network, such as email, telephone or the US mail. And, though some P2P networks are “closed,” requiring invitations or other credentials for participation – a safeguard typically used for quality control as well as privacy – the vast majority of file sharing takes place on “open” networks, which are as accessible and subject to surveillance as the web, and far more transparent than email or instant messaging.

¶ 3 Leave a comment on paragraph 3 0 Not only are there dozens of rival back-end technology platforms for P2P file sharing and hundreds of front-ends via which to access them, there is also a wide range of different architectures for the networks themselves.[1] Some platforms, such as the original Napster, are centralized, meaning that all the information about who is searching for what travels through a single server, which has a kind of god’s-eye-view on the activities of each peer. Other networks, such as Gnutella, are unstructured; there is no center to the network, and each peer only has a limited view of the network based on information from the other peers to which it is randomly connected. While Napster and Gnutella facilitate the exchange of complete files, such as MP3s, between any two given peers, BitTorrent (currently the most popular P2P protocol) breaks down files into their component bits, and requires that users go through a somewhat complex process to collect and reassemble those bits into a complete file. A peer enters the network by opening a “torrent” – a small text document containing information about the file in question, generally hosted on a web site and discoverable through a specialized search engine called an “index.” The torrent then directs the user’s software to a “tracker,” which is a database containing a list of other peers that currently have all or part of the file. The user’s computer then collects bits of the file from each of these other peers, and once it has all of the file’s bits, it reconstructs them into the file itself. At no point does an individual peer deliver an entire song, movie, document, or other file directly to another individual peer, nor is there a central node from which a god’s-eye-view of the network is attainable. While there are several other variations on P2P network architectures, these are the three primary flavors at the time of writing – the vanilla, chocolate and strawberry of file sharing.

¶ 4 Leave a comment on paragraph 4 0 These distinctions are not academic, nor sheer computer science geekery. They have profound implications for how legally culpable, surveilable, and censorable the networks themselves are. Napster, due to its centralized architecture, was the most vulnerable to both legal and technical challenges. Because the service was capable of identifying copyrighted files on its servers and restricting their transfer, it was found liable for “contributory infringement” and “vicarious infringement” for the unlicensed sharing behaviors of its users.[2] Once its servers were shut down, the service became unusable. The same could not be said of more decentralized file sharing services such as Grokster and LimeWire.[3] Because these file sharing services lacked network oversight and therefore could not be found liable for contributory or vicarious infringement, they were ultimately found liable for “inducement” of copyright infringement, a new legal standard that emerged from the US Supreme Court’s decision in the Grokster case.[4] Yet despite these rulings, the networks were not as easy to shut down as Napster was. For instance, even though LimeWire stopped publishing its software and remotely disabled many of its users’ copies via a “back door” in the program’s code, an open-source “Pirate Edition” of the software emerged two days later, and remains fully functional and active at the time of writing despite the efforts of LimeWire and the RIAA to shut it down.[5]

¶ 5 Leave a comment on paragraph 5 0 BitTorrent is the most difficult “flavor” of P2P to successfully prosecute or contain. Because the BitTorrent protocol is freely available for programmers to use, there are many open-source software front-ends based on it, each of which operates completely independently of its developer, BitTorrent Inc. And because the sharing process is broken up into so many moving parts and reduced to the scale of bits, issues of legal liability become far more complex. Is hosting or contributing to an index a violation of copyright, even though the torrent file is only a text file about a copyrighted work, rather than the work itself? Is joining or maintaining a tracker a violation of copyright, even if the tracker is neither contributing to nor inducing infringement, in a legal sense? Is there a de minimis, or a minimum number of digital 1s and 0s that need to be shared by a given peer before they constitute an infringement? Would sharing a single bit of data, technically indistinguishable from any other bit of data on the internet, constitute infringement if it were related to a torrent for a song or a film? These questions have yet to be definitively addressed in by either legislation or caselaw, although the music and film industries, as well as several governments around the globe, have taken legal and quasi-legal action against many parties including scores of trackers and hundreds of thousands of individual BitTorrent users.

¶ 6 Leave a comment on paragraph 6 0 In short, P2P file sharing is not simply a piece of “rogue technology” that enables “pirates” to infringe on copyrights. It is a diverse assortment of technologies and platforms with a broad range of uses in a variety of different contexts. While some specific P2P architectures are vulnerable to some varieties of legal challenges and technological restrictions, others are technically legal or as yet untested, and many remain impervious to any kind of legal or technological regulation except perhaps total surveillance or closure of all digital communications networks. And, as network technologies continue to evolve in the coming years, it is likely that the range and complexity of P2P platforms will increase as well. While there is no preordained path for social or technological development, it seems very likely that in the near future, our mobile devices will be able to establish ad hoc, locally-aware P2P networks[6] that eschew internet traffic altogether and remain virtually undetectable and unsurveillable by centralized authorities. Torrent tracker The Pirate Bay has already made moves in a similar direction, announcing plans on its blog to launch low-orbit drone airplanes hosting its servers.[7] Given the likelihood that technological developments such as these will continue to outpace efforts at policing and enforcement, any economic or legal strategy that attempts to contain P2P rather than accept and embrace it is very likely to fail.