How the internet works

Sending emails
Email is another popular use for the internet. Millions of messages are sent every second, so how do they all get where they’re supposed to go?

Much like traditional letters, electronic messages all carry an address. To email us, for instance, you would send a message to letters@computeractive.co.uk. The bit before the @ symbol is the local part of the address (ie, the person or department it’s going to). The bit after the @ is the domain where their address ‘lives’.

When an email is sent it goes first to the ISP’s email server. This then looks up the domain part of the email address and finds the associated IP address or the recipient’s computer. You’ll remember that this information is stored the special list called the Domain Name Registry. When the message turns up at the right server, it looks at the local part of the address and drops it into that person’s mail box. When they next send and receive email, they pick up the message. It really is like the postal service – you post a letter, it goes to your local post office for sorting, they send it off to another post office which then organises the mail into local addresses and then delivers it to the recipient.

Logging off
So there you have it – our guide to what goes on behind the scenes of the internet. We could continue distilling down the technology almost indefinitely, to the binary ones and zeros that constitute all data flowing across the web. However, we’ll wrap up by considering what keeps all this data flowing. The key is packets. These are essentially small bundles of data (those ones and zeroes) packaged up with an embedded destination address. One email message, for example, could be broken down into hundreds of packets. Each of these will travel independently over the internet.

Though this may sound inefficient, packets are really what keep the internet flowing. Because these small chunks can take different paths across the internet it doesn’t matter if any one server computer develops a fault or is unavailable.

So, it would be impossible to switch off the internet. Well, unless we all switch off our computers at the same time. So let’s all agree to avoid that.

Going behind the scenes
Here are our favourite websites for finding out what the internet’s up to. The first one is useful if you’ve ever visited a site that won’t display and is at www.downforeveryoneorjustme.com.

If you want to know the IP address of your own PC, just visit www.whatismyipaddress.com and it will tell you, along with the name of your ISP.

Finally, want to know who’s really running a particular site? Go to http://whois.domaintools.com and type the name of the website into the empty box. Press Enter and it will list who owns the site, their postal address and so on.