Free lesson with a practice sheet
How the internet works
See how the internet connects devices: clients, servers, routers, IP addresses, domain names and data packets.
Let us begin
The big idea
When you open a web page, it appears in a moment. Behind that moment, many machines in different places pass messages to each other. Let us see how it works, step by step.
The internet is a huge network of networks. Millions of computers, phones and other machines are linked by cables, radio waves and satellites. A router connects the devices in your home to the wider network.
Your device is the client. It asks for something, such as a web page. A server is a powerful computer that stores web pages and sends them when asked. This is the client-server model.
Every device on the internet has an address called an IP address. People prefer names, so we use domain names such as the name of a school website. A system called DNS works like a phone book: it turns the name into the number address.
Data does not travel in one piece. It is cut into small parts called packets. Each packet has the sender, the receiver and its number. Packets may take different routes and are put back in order at the end.
The web (websites) is only one service that runs on the internet, just as shops run on roads. Email and video calls also use the internet. A padlock in the address bar means the connection is encrypted, so others cannot read your data on the way.
Worked examples
See how it works
Opening a web page
Step 1: you type the website name. Step 2: DNS finds the IP address. Step 3: your device sends a request to that server. Step 4: the server sends back the page in packets. Step 5: your browser puts them together and shows the page.
Counting packets
A file of 1,000 KB is sent in packets of 250 KB each. Number of packets = 1,000 / 250 = 4. If one packet goes missing, the receiver can ask for just that one again.
Internet or web?
Sending an email uses the internet but is not a web page. A news website is on the web, and the web runs on the internet. So the internet is the roads and the web is one kind of shop on those roads.
Try it at home
Packet post game
You will need
- a sheet of paper
- pencil
- a friend or family member
What to do
Write a short message of about 12 words on the paper.
Tear the paper into 4 pieces, with about 3 words on each. Number the pieces 1 to 4.
Shuffle the pieces and give them to your friend without telling the order.
Your friend puts the pieces in order using the numbers and reads the message.
Now remove one piece. Can your friend tell which number is missing? That is why packets are numbered.
This is a paper-only game. No device or internet is needed. An adult can help tear the paper evenly.
Fun fact
Most of the internet traffic between countries travels through cables under the sea, where data moves as flashes of light in glass fibres.
Practice sheet
Check what you learned
Practice sheet: How the internet works (Classes 9-10, Computers and coding)
- What is the internet in simple words?
- In the client-server model, what is the client and what is the server?
- What is a router used for at home?
- What is an IP address?
- What does DNS do?
- Why is data sent as packets?
- A file of 600 KB is sent in packets of 150 KB. How many packets are needed?
- What is the difference between the internet and the web?
- What does the padlock sign in the address bar tell you?
- List in order the steps when you open a website.
Answer key
Answers: How the internet works
- A huge network of networks that connects computers and other devices all over the world.
- The client is the device that asks, such as your phone. The server is the computer that stores things and sends them back.
- It connects the devices in your home to the internet (and to each other).
- A number that acts as the address of a device on the network.
- It turns a website name into the IP address, like a phone book.
- Small packets can take different routes, are easier to resend if lost, and share the network fairly with others.
- 600 / 150 = 4 packets.
- The internet is the network itself. The web is one service (websites) that runs on it. Email also uses the internet.
- The connection is encrypted, so others cannot easily read your data on the way.
- Type the name, DNS finds the IP address, a request goes to the server, the server sends packets back, and the browser puts them together to show the page.