What Is the Internet and How Does It Work? KS3 Computing Guide

The internet is a global network of networks — billions of devices connected together so they can send and receive data. It was developed in the late 1960s and has grown into the infrastructure that supports email, streaming, social media, and the World Wide Web. Understanding how it works is a core part of the KS3 computing curriculum.

What exactly is the internet?

The internet is a network of networks. Each device connected to it — your phone, your laptop, a school server, a data centre in Iceland — is part of a smaller local network, and those local networks are connected to each other via a system of physical cables (copper, fibre-optic) and wireless signals (Wi-Fi, 4G, 5G).

The key idea is that no single organisation owns or controls the internet. It is a decentralised system designed so that data can find multiple routes from one point to another. If one route goes down, data can be rerouted. This was originally designed during the Cold War to create a communication system that could survive a nuclear attack on any single node.

The internet vs the World Wide Web

These two terms are often used interchangeably, but they refer to different things:

The World Wide Web is one service that runs on top of the internet, just as email is another service. You could have the internet without the Web (and it existed for around 20 years before Berners-Lee invented the Web in 1989), but you cannot have the Web without the internet.

How does data travel across the internet?

Data does not travel across the internet as one continuous stream. Instead, it is broken into small chunks called packets. Here is the basic process:

1. You request data — for example, you click on a YouTube video. Your device sends a request.
2. The data is broken into packets — the video file is divided into thousands of small packets, each labelled with the sender's address, the recipient's address, and the order in which the packet belongs.
3. Packets travel independently — each packet may take a different route across the internet, passing through multiple routers (devices that direct traffic).
4. Packets are reassembled — when all the packets arrive at your device, they are reassembled in the correct order and the video plays.

This system is called packet switching and it is fundamental to how the internet works. It is efficient (multiple packets from different users can share the same cable simultaneously) and resilient (if one route is blocked, packets can be rerouted).

What is an IP address?

Every device on the internet has a unique IP address (Internet Protocol address) — a numerical label that identifies it on the network, similar to a postal address for a house. Without IP addresses, data would have no way of knowing where to go.

IPv4 addresses look like this: 192.168.1.1 (four numbers separated by dots, each between 0 and 255). There are approximately 4.3 billion possible IPv4 addresses — a number that turned out to be far too small as the internet grew. The newer standard, IPv6, uses longer addresses (e.g. 2001:0db8:85a3:0000:0000:8a2e:0370:7334) and supports an astronomically larger number of devices.

Most devices do not have a permanent IP address — they are assigned a temporary one by their internet service provider (ISP) whenever they connect. This is called a dynamic IP address.

What are protocols and why do they matter?

A protocol is a set of rules that governs how data is sent, received, and interpreted across a network. Protocols are essential because the internet connects billions of different devices made by different manufacturers running different software — without agreed rules, none of them could communicate.

Key protocols at KS3:

• TCP/IP (Transmission Control Protocol / Internet Protocol): The foundational protocols of the internet. IP handles addressing and routing; TCP ensures that packets arrive completely and in the correct order.
• HTTP/HTTPS (HyperText Transfer Protocol / Secure): Used by web browsers to request and receive web pages. HTTPS adds encryption, so data cannot be read by a third party intercepting the connection.
• DNS (Domain Name System): Translates human-readable web addresses (like www.bbc.co.uk) into numerical IP addresses that computers can use. DNS is sometimes called the "phone book" of the internet.

What happens when you type a web address?

Here is the full journey, step by step, when you type https://www.bbc.co.uk into your browser:

1. DNS lookup: Your device contacts a DNS server to convert www.bbc.co.uk into an IP address (e.g. 212.58.237.252).
2. TCP connection: Your browser establishes a TCP connection with the BBC's web server at that IP address.
3. HTTPS handshake: Your browser and the server exchange encryption keys so the connection is secure.
4. HTTP request: Your browser sends an HTTP GET request: "Please send me the homepage."
5. Server response: The BBC's server sends back the HTML, CSS, and JavaScript files that make up the page, broken into packets.
6. Rendering: Your browser reassembles the packets and renders the page on your screen.

This entire process typically takes less than half a second.

Key terms for KS3 computing

Frequently asked questions

What is the difference between the internet and the World Wide Web?

The internet is the physical and logical infrastructure — the global network of cables, routers, and wireless signals that connects billions of devices. The World Wide Web is one service that runs on top of this infrastructure: a collection of websites and linked web pages that you access through a browser. The internet existed for about 20 years before Tim Berners-Lee invented the Web in 1989. Other services also run on the internet — email, video calling, and online gaming all use internet infrastructure but are not part of the World Wide Web.

How does data actually travel across the internet?

Data travels across the internet as small chunks called packets. When you request a file — a video, a web page, or an email — it is broken into thousands of packets, each labelled with the sender's address, the recipient's address, and the packet's position in the sequence. These packets travel independently across the network, potentially taking different routes, and are reassembled into the correct order when they arrive at your device. This process, called packet switching, makes the internet fast, efficient, and resilient to single points of failure.

What is an IP address and why does every device need one?

An IP address is a unique numerical label assigned to every device connected to the internet, similar to how every house has a unique postal address. Without IP addresses, packets of data would have no way of knowing where to go. IPv4 addresses have the format 192.168.0.1 and allow approximately 4.3 billion unique addresses. Because there are now more internet-connected devices than IPv4 addresses can accommodate, a newer format called IPv6 has been introduced with a much larger address space.

What is DNS and why is it important?

DNS stands for Domain Name System. It is a protocol that converts human-readable domain names (like www.gov.uk) into the numerical IP addresses that computers use to locate servers. Without DNS, you would need to memorise a string of numbers for every website you visit. DNS servers act like a phone book for the internet: your device contacts a DNS server, says "I want to visit bbc.co.uk — what is its IP address?" and the DNS server replies with the correct number so your browser can connect.

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