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On Location: Implementing Icarus P2P-Blocking Software

All this makes for an intriguing debate: limited resources, university policies and copyright infringement versus privacy and freedom. For now, however, we'll leave that cerebral discussion to philosophers like David Joachim (see "The Enforcers," page 40) and focus on the technology behind Icarus. To paraphrase Descartes, we network, therefore we are.

Whose P2P?

First, let's define our terms. P2P connections are prohibited under UF's residence hall "no server" network policy. Some people mistakenly think that P2P sessions involve a community of peers working together with equal responsibilities--a serverless environment that would seem to exclude this class of application from UF's policy. Although it's true that P2P machines are peers, whenever one of those peers makes resources available to another, as it does when sharing an MP3 file, for example, that client machine becomes a server--a UF policy no-no.

The P2P category is broad, encompassing applications ranging from real-time Web conferencing to Kazaa and its ilk, which let a dynamic community of users share music and other files.

With P2P network nodes freely alternating as clients and servers, how--or even whether--a particular node will participate at any given moment is unpredictable. As P2P expert Clay Shirky explains, "P2P is a class of application that takes advantage of resources--storage, cycles, content, human presence--available at the edges of the Internet. Because accessing these decentralized resources means operating in an environment of unstable connectivity and unpredictable IP addresses, P2P nodes must operate outside the DNS system and have significant or total autonomy from central servers."

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