WHAT IS THE INTERNET?
This giant network can seem almost ethereal.
For the most part we connect to it without wires, sending and receiving data as if from thin air. We can scroll through cat pictures in the middle of a field and stream movies straight from the cloud. But despite that airy feeling, the nuts and bolts of the internet are very solid and very down to Earth. At its core, it’s a network of billions of miles of wires end-to-end, and millions of computers.
Your internet connection begins at the modem that’s set up in your house. It connects via a wire to a socket in the wall, which links to a box outside. That box connects via still more wires to a network of cables under the ground. Together they convert radio waves to electrical signals to fibre-optic pulses and back again.
At every connection point in the underground network, there are junction boxes called routers. Their job is to work out the best way to pass data from your computer to the computer you’re trying to communicate with. They use your IP addresses to work out where the data should go. The internet is so massive, and changes so rapidly, that it would be impossible for every router to know the IP address of every computer, so each one only cares about its local network. They each maintain an address book called a routing table. It shows the paths through the network to all the local IP addresses.
If a message arrives for a computer that the router doesn’t recognise, it passes it on to a router higher up in the local network. If that router doesn’t recognise the IP address either, it passes it up again. Eventually, it reaches the top of the network: the backbone. This is the motorway of the internet. Its job is to send traffic around the world, across both land and sea. The data passes from backbone to backbone until it reaches the network closest to its destination. Then it travels down through the layers of local routers until it arrives at the computer with the matching IP address.
These destinations are often data centres, buildings filled with rack upon rack of powerful computers called servers. They contain and manage everything from your social media profile to your email account, your bank and your holiday photographs.