Thursday, 24 September 2009

Tech

Pigeons, packets and post

The other week most media outlets picked up on the story of Winston the Pigeon. This was clearly just a publicity coup ("coo-coo-coo").

The story was that a company in South Africa was so fed up with the speed of their broadband that they discovered it was faster to transfer data by carrier pigeon. The unwritten subtext was a comment on the state of broadband provision in South Africa.

But what happens if you run the numbers? Winston transferred 4 GBytes in two hours. That's equivalent to a sustained rate of 4.5 Mbit/s: hardly shabby, and nearly 1 Mbit/s higher than the average download throughput achieved by users in the UK.

It's even more remarkable if you assume that the constraint on broadband was the upload speed rather than the download speed. The "A" in "ADSL" stands for "asymmetric": the maximum rate at which you can send data is far less than the rate at which you can receive. So if you're sending data from one ADSL line to another it's not the headline "up to 8 Mbit/s download" rate that's limiting you; it's the maximum upload rate which for most people in the UK is a paltry 448 Kbit/s. At that rate it would take over twenty hours to transfer the full 4 GBytes.

So it's hardly a surprise the pigeon won.

What is worth observing is that twenty hour figure. It means that if you want to transfer over 4 GByte of data between any two points in the UK, no matter where they are it's probably quicker to move the data physically rather than electronically. (Now do you see why data CDs could get lost in the post?)

For the pigeon lovers out there, the Internet Engineering Task Force first described how to use "avian carriers" to extend the Internet back in 1990, although it took a further eleven years before this mechanism was demonstrated in practice.

Posted by pab at 22:47 | Comments will be back later in the year. Please email me instead!