A computer network is two or more computing devices connected together to share data, resources, and services. The internet is the largest computer network in the world — a global network of billions of connected devices.
Why do we use computer networks?
Networks exist because sharing is more efficient than duplicating. Before networks, every computer was a standalone island: you saved files to a floppy disk, walked to another machine, and copied them across. Networks changed that by allowing:
- Data sharing — files, emails, and documents transferred instantly between devices
- Resource sharing — a single printer or server used by many machines
- Communication — messages, video calls, and collaboration in real time
- Centralised storage — data stored once and accessed from any device on the network
The DfE's national curriculum for computing requires KS3 students to "understand the hardware and software components that make up computer systems, and how they communicate with one another." Networks are central to that requirement.
What are the main types of network?
At KS3, students need to know two primary network types: LAN and WAN.
| Network type | Full name | Typical coverage | Example |
|---|---|---|---|
| LAN | Local Area Network | A single building or site | A school network, a home Wi-Fi |
| WAN | Wide Area Network | Multiple cities, countries, or globally | The internet; a company's offices in different countries |
A LAN connects devices within a limited area and is typically owned and managed by a single organisation. The school network you log in to every morning is a LAN.
A WAN connects multiple LANs across larger distances, usually via leased telephone lines, fibre optic cables, or wireless connections. The internet is a WAN, but companies can also create private WANs to link offices in different cities.
Other network types worth knowing
- MAN (Metropolitan Area Network) — covers a town or city; less commonly tested at KS3 but useful to recognise.
- PAN (Personal Area Network) — very short-range connections between personal devices, such as a phone connected to headphones via Bluetooth.
What hardware makes a network work?
Networks require physical and logical components to function.
| Component | What it does |
|---|---|
| Router | Directs data packets between networks; connects a home or school LAN to the internet |
| Switch | Connects devices within a LAN and sends data only to the intended device (unlike a hub, which broadcasts to all) |
| Network Interface Card (NIC) | Hardware in each device that allows it to connect to a network |
| Modem | Converts digital signals from a computer into signals that can travel over telephone lines and back again |
| Wireless Access Point (WAP) | Allows devices to connect to a network wirelessly (Wi-Fi) |
| Server | A powerful computer that provides services or stores data for other devices (clients) on the network |
The client-server model is the dominant architecture for most networks: clients (your laptop, phone) make requests; servers (a web server, file server, email server) respond. In a home network, your router performs many of these functions in one device.
How does data travel across a network?
Data does not travel as one continuous stream across a network. It is broken into smaller units called packets, which then travel independently and are reassembled at the destination. This process is managed by a set of rules called protocols.
What is a packet?
A packet typically contains:
- Header — source address, destination address, packet number (so reassembly is possible)
- Payload — a chunk of the actual data being sent
- Trailer — error-checking information
Breaking data into packets has key advantages:
- If one packet is corrupted or lost, only that packet needs to be resent, not the whole message.
- Packets from different sources can share the same network link simultaneously (packet switching).
- Each packet can take a different route to the destination, making the network more robust.
What are protocols?
A protocol is a set of agreed rules for how data is formatted and transmitted. Without protocols, devices from different manufacturers could not communicate. The most important protocols at KS3 are:
| Protocol | What it does |
|---|---|
| TCP/IP | The foundation of the internet: TCP breaks data into packets and reassembles them; IP routes them |
| HTTP/HTTPS | Used for loading web pages; HTTPS is the secure, encrypted version |
| FTP | File Transfer Protocol — used to transfer files between servers and clients |
| SMTP | Used for sending email |
What is the difference between the internet and the World Wide Web?
This is one of the most commonly confused distinctions in KS3 computing.
- The internet is the global network of interconnected computers — the physical infrastructure of cables, routers, and wireless links.
- The World Wide Web (WWW) is a service that runs over the internet — specifically, the system of websites and hyperlinks accessed using HTTP/HTTPS.
The internet also carries email, video streaming, online gaming, and file transfers. The web is just one of many services delivered over that infrastructure.
Worked example: what happens when you load a web page?
When you type www.bbc.co.uk into a browser, the following happens:
- DNS lookup — your device asks a Domain Name System (DNS) server to translate the human-readable domain name into an IP address (e.g. 151.101.0.81).
- Connection — your device sends a request via your router and ISP to the BBC's web server.
- Data is split into packets — the server sends the web page's HTML, CSS, and images as separate packets.
- Packets travel independently — each packet may take a different route across the internet.
- Reassembly — TCP reassembles the packets in order on your device.
- Rendering — your browser converts the received files into the visible web page.
The whole process typically takes less than one second for a well-optimised page.
Frequently asked questions
What is the difference between a LAN and a WAN?
A Local Area Network (LAN) connects devices within a single site, such as a school or home. A Wide Area Network (WAN) connects devices across large distances — multiple cities, countries, or globally. The internet is the largest WAN in existence, connecting billions of devices worldwide.
What is a data packet in networking?
A data packet is a small unit into which data is divided before being sent across a network. Each packet contains a header (source and destination addresses, packet number), a payload (a chunk of the data), and a trailer (error-checking information). Packets travel independently and are reassembled at the destination.
What does a router do in a network?
A router directs data packets between different networks. In a home or school setting, the router connects the local network (LAN) to the internet (WAN), deciding the best path for packets to travel. Routers use the IP address in each packet's header to make routing decisions.
What is the difference between the internet and the web?
The internet is the global physical network of connected computers — cables, routers, wireless links, and the protocols that govern how data travels. The World Wide Web is a service that runs over the internet, consisting of web pages linked by hyperlinks and accessed via HTTP or HTTPS. Email, streaming, and online gaming also run over the internet but are not part of the web.
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