New Internationalist 286
The Internet explained
Picture a maze-like garden of forking paths with each path
connected to its neighbour and thousands of new paths
being added daily. That's roughly how the Internet looks.
But how does a message travel along those pathways?
1 Suppose you're in Aotearoa/New Zealand and you want to send a message to your uncle in Boston. Whether it's a brief letter, a mathematical formula or a photo of your dog the 'information' is all treated in the same way. First it is digitized, that is, turned into the mathematical language that computers use to communicate.
2 The digitized data in the form of electronic blips then travels along phone lines to your local provider or 'server'. Here it's broken down into chunks called 'packets'. Each 'packet' is labelled with the address of the recipient, in this case something like [email protected]
3 A computer called a 'router' next reads each addressed packet and sends your data in the right general direction to the next 'server'. None of the 'routers' has a map of the whole Internet. They only have an idea of their little patch of it and the best way to get to the next point in the network. This process continues from server to server, mostly on telephone lines leased from existing telephone companies.
4 Depending on traffic flow different parts of the same message may be sent by entirely different routes, only to be electronically stitched back together at their final destination. Since electronic communication is for all practical purposes instantaneous it doesn't matter whether your uncle's message goes via Sydney or San Francisco. Eventually, providing there are no drastic system crashes en route, your message arrives at the computer of the Internet service provider that your uncle is signed up with.
5 Next time he checks his electronic mail he'll find your re-assembled message on the screen in front of him.