BBC Future

How does the internet really work?

Upload a photo or send an email, and what happens next? BBC Factomania has a two-minute guide to the lightning-speed journey that happens as soon as you press click.

There are over 300 million images uploaded to Facebook every day, and over 5 billion gigabytes of material on the web in total, but have you ever thought how it all gets there?

This is how the internet works… get ready….

One click downloads, say, a picture from a cloud server. The request is picked up by your computer, stuffed into a packet (a cluster of electrical pulses), stamped with the address of the cloud server; and blasted out of your house, or wherever you are. Along with trillions of packets all around it, your request reaches hub computers that can read the address and pass it from hub to hub along the least congested route, until it reaches the sea.

Here, a landing station illuminates an underwater fibre optic superhighway cable, transforms your request from electricity to pulses of light, and fires it off. Your download photo request travels under the sea on a 10 gigabyte per second wavelength of light along with 10,000 other download requests, video streams and emails. In the same fibre are up to 70 other message wavelengths, and there are eight fibres in each cable.

Thanks to this, your requests can travel several thousand kilometres in a fraction of a section. Their destination is one of over 100 million server farms, found anywhere from Sweden to the US Midwest. These servers would quickly heat up as they crunch numbers, so  they use around 1.5% of the world’s electricity just to keep our data cool. A digital picture is around 5,000 times the size of a data packet, so to send it back the server has to smash it into 5,000 pieces which will then travel back to you in little bits before reassembling itself. Simple, really.

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