Introduction to cyber security: stay safe online
Introduction to cyber security: stay safe online

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

3.3 From numbers to names

When we type an address (such as into a browser, the address is translated into a unique IP address by a name server, called a Domain Name Server (DNS), located somewhere on the internet. This IP address is attached to every IP datagram destined for the Open University server.

As an example we will use an IP datagram belonging to an email being sent to Bob who works in the coffee bar at Big University in America (Bob’s address is The address is sorted from the most general part of the address to the most specific. First of all, the name server on the sender’s machine makes a request across the internet to a computer which holds the addresses of all American universities (most of which use .edu at the end of their address) asking for the IP number of Assuming that exists, the .edu name server then responds with the IP number for the name server at Big University.

The sender’s machine then uses that IP number to make a link to the name server at Big University and requests the IP number of the coffee shop computer used by Bob. The name server will then respond with the address of the coffee shop. The IP datagrams can then all be addressed correctly and sent into the network.

Up until 2019, the DNS information requested was sent as plain text and could be intercepted even when the data being sent or requested was encrypted. From 2019, it has become possible for DNS requests to be encrypted. In Firefox browser go to Settings, then Network settings and select the enable DNS over HTTPS checkbox.

Chrome 78 is also experimenting with this feature, which can be enabled by browsing to ‘chrome://flags/’ in your Chrome browser, searching for ‘dns-over-https’ and enabling. You will have to restart the browser for this change to take effect.

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371