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Peer-to-Peer (P2P) Resource Sharing


3. Potential problems with peer-to-peer software

3.1. Bandwidth utilisation

The chief concern with peer-to-peer software, at least from the point of view of the network administrators, is in terms of bandwidth utilisation. The very nature of peer-to-peer networks means that for every unit of data downloaded by a given node, that unit of data may subsequently be sent from that node to many others. Well-connected nodes are particularly popular and the upload bandwidth available from a node on the University network is typically hundreds of times that of a node on a standard domestic broadband connection. Many applications are purposely designed to maximise usage of available bandwidth, even if this is to the detriment of other uses and users of the network.

Many peer-to-peer applications unfortunately give the user little or no degree of control over how their bandwidth may be used, other than disabling the application (and in some cases, even that much is nontrivial). It is natural for P2P networks to be concerned that some users may mostly be downloaders of content without contributing much to other users of the network. However, if for example one could instruct the application that for each item downloaded that it should serve out the equivalent of no more than three complete copies of said item, consuming no more than 5 megabits of bandwidth at any one time, then one might have a certain confidence that it would not completely overwhelm the local network infrastructure.

Bandwidth that seems insignificant for one user will soon add up when scaled up to the many thousands of users connected to Oxford University's networks, or the hundreds on a single college network. Many colleges have comparatively slow connections to the rest of the University network, particularly in view of the number of students, but cannot necessarily justify the expense of an upgrade to a faster connection. Some college annexes may be served over wireless links or commercial connections rather than the University's optical fibre network, which restricts bandwidth still further.

It is one thing attempting to justify a network upgrade on the basis of a genuine academic requirement, such as the petabytes of data expected from CERN when their latest collider comes online. It is another thing trying to do it purely to cope with the demands of high-bandwidth recreational usage. Taxpayers and research councils tend to like to see their money being spent more wisely! On most networks within the University, reasonable recreational usage of the network is expected and tolerated, but measures may be taken in the event of excessive utilisation so that resources can be fairly shared by all.

3.3. Security issues

It is wise to be cautious before installing any software, and peer-to-peer applications are no exception. Insecure applications may open up a machine to the danger of external attack from malicious third parties. Additionally, software from some sources may come bundled with malicious "spyware" which invades the user's privacy, or worse. There are known cases of peer-to-peer applications incorporating spyware.

Saying that, many peer-to-peer-based applications, provided that they are obtained from a trustworthy source, will not be intentionally malicious. However, as with all software, security flaws may be discovered from time to time and so it is important to ensure that it is kept up to date with respect to vendor patches.

Up: Contents Previous: 2. Introduction Next: 4. University regulations on use of peer-to-peer applications


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Maintained by: OUCS Webmaster (webmaster@rt.oucs.ox.ac.uk) July 2010. Robin Stevens, based upon an original document by Peter Higginbotham.
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