Skype as a Bandwidth Hog?

by on September 25, 2006 · 20 comments

Ars has an interesting story about three California colleges that have decided to ban Skype from its campus. The school administrators have what strikes me as a puzzling attitude toward the service, describing it as a “potentially illegal waste of resources,” without explaining what might be illegal about it. Perhaps they’ve somehow gotten the erroneous impression that there’s something inherently illicit about “grid-computing-like” network applications.

Aside from legal concerns, the other issue seems to be bandwidth:

according to the Office of Information Technology, the chief problem comes when a Skype client acts as a “supernode” and makes itself available to relay calls made by other users. Having numerous supernodes on a school network increases bandwidth consumption and has a detrimental impact on connectivity, according to the memo. Anecdotal reports from individual Skype users reveal that bandwidth consumption can increase by as much as an entire gigabyte per month for a single Skype client when it acts as a supernode.

If my math is right, 1 gigabyte per month is roughly 3 kilobits per second, a trivial amount of bandwidth on a modern campus network. Even if the bandwidth is concentrated in shorter bursts–say, if the whole gigabyte is transmitted in a single hour–that’s still a rate of only 2.2 megabits per second–roughly the bandwidth of a typical DSL line. This is not a particularly abusive use of the network.

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