October 22nd, 2009

Kettering, CS

What's the bandwidth of a carrier pigeon?

Some of you are familiar with Andrew Tanenbaum's famous quote: "Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. " It's a favorite exercise to assign to students in a networking class.

The idea is as follows. Assume you've got a huge amount of data you want to send across town ... say, enough to fill a hundred magnetic tapes. (Ok, it's a really old idea ... stay with me here.) If you calculate the amount of time it takes to write all the data to tape, haul all the tapes outside to a pickup truck, drive across town, haul the tapes inside, and read all the data off the tapes, you have a measure of bandwidth: bits transferred per unit time. Now, compare that number with network speeds commonly available on wide area networks. Often, the results are surprising ... namely, that the pickup truck can beat most networks (at least, the networks available at the time). It's an interesting gedankenexperiment.

Well ... someone's updated it, for real this time. An office in South Africa was having severe problems with their ADSL line, so they decided to see if they could do any better. They got a carrier pigeon, stuck a 4GB data stick to its leg, then sent it to the office across town. By the time the carrier pigeon had finished its work, the ADSL network had only copied 4% of the same amount of data.

Guess it's time to clean up some of those notes ...

SA pigeon 'faster than broadband'(from BBC News)
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