In simple terms
A friendly intro before the formal notes — no formulas yet.
From One Device to the World
A computer network is simply two or more computers linked together to share resources, like files or an internet connection. The internet is the ultimate example, connecting billions of devices globally.
Think of a network like a postal service. A Personal Area Network (PAN) is like passing a note to the person next to you. A Local Area Network (LAN) is like the internal mail system in an office building. A Wide Area Network (WAN) is the entire national and international postal system that connects all the buildings.
- 1
A single computer is a standalone 'node'. It can store data but cannot share it electronically.
- 2
Connect two or more devices in a small area, like a home. This forms a Local Area Network (LAN) for sharing files or a printer.
- 3
Introduce a central, powerful computer (a server) to manage resources for other computers (clients). This is the client-server model, common in schools and businesses.
- 4
Connect millions of these individual networks across the globe using specialised hardware like routers. This vast, interconnected system is the internet.
Explore the concept
Use the live diagram and synced steps — play it or tap a step card to walk through.
Full topic notes
Formal explanation with the rigour you need for the exam.
Classifying Networks by Scale
Networks are primarily categorised by their geographical size. Understanding these classifications is crucial for describing different network scenarios. The hardware, technology, and ownership of a network are often dictated by its scale.
PAN (Personal Area Network): The smallest type of network, spanning just a few metres. It's used for connecting personal devices, often using wireless technologies like Bluetooth. For example, connecting a wireless headset to a smartphone.
LAN (Local Area Network): Covers a limited area like a home, office, or school. Devices are connected via switches and cables (Ethernet) or wirelessly (WLAN - Wireless LAN). The organisation that owns the LAN also owns the networking equipment.
WAN (Wide Area Network): Spans a large geographical area, connecting LANs together. The internet is the ultimate example of a WAN. WANs rely on infrastructure provided by telecommunications companies, such as fibre optic cables, satellite links, or microwave relays.
Network Architecture: Client-Server vs. Peer-to-Peer
Beyond size, networks are defined by how their members interact. There are two main models: the centrally-managed client-server model and the decentralised peer-to-peer model.
Client-Server Model: In this model, a powerful central computer called a server provides resources and services (like file storage, web pages, or authentication). Other devices, called clients, connect to the server to request these services. This is the dominant model for the World Wide Web and most business networks.
Advantages: Centralised security, backups, and administration. Scalable by adding more clients or upgrading the server.
Disadvantages: Server failure can disable the network. Can be expensive to purchase and maintain a dedicated server. Server can become a bottleneck if overloaded.
Peer-to-Peer (P2P) Model: All computers on the network have equal status and are called 'peers'. Each peer can act as both a client and a server, sharing its files and resources directly with other peers. There is no central server.
Advantages: Easy to set up and low cost. More resilient, as the failure of one peer doesn't bring down the whole network.
Disadvantages: Security is decentralised and harder to manage. Backups must be performed on each individual peer. Locating resources can be less efficient than with a central server.
When asked to compare Client-Server and P2P, always discuss specific aspects like security, cost, setup, scalability, and what happens if a device fails. Use examples to support your points.
The Internet and its Core Technology
The internet is not a single entity but a massive, global WAN—a 'network of networks'. It connects private, public, academic, business, and government networks using a standardised suite of communication protocols (TCP/IP). Its operation relies on two key concepts: routers and packet switching.
Packet Switching: When you send data (e.g., an email), it's not sent as one continuous stream. It is broken into small, numbered chunks called packets. Each packet contains a portion of the data, the destination address, and its sequence number. Packets are sent independently, possibly taking different routes, and are reassembled in the correct order at the destination. This is efficient and robust; if one route is congested, packets can be sent via another.
Routers: These are the 'traffic police' of the internet. They are specialised computers that connect different networks together. When a router receives a packet, it reads the destination address and forwards the packet on to the next network on the best path towards its final destination.
Worked examples
See the formulas applied — reveal one step at a time, like the exam.
A school with 500 computers needs a network for students to save their work to a central location and access shared software. Which network model, Client-Server or Peer-to-Peer, would be more suitable? Justify your choice with two reasons.
- 1
The Client-Server model would be more suitable.
A video file is 240 Megabytes (MB). Calculate the theoretical minimum time it would take to transfer this file over a network connection with a bandwidth of 80 Megabits per second (Mbps).
- 1
Understand the units: The file size is in Megabytes (MB) and the speed is in Megabits per second (Mbps). We need to use the same unit. The key is that 1 Byte = 8 bits.
How it all connects
The big idea sits in the middle — tap a linked idea to explore the link.
Tap a linked idea to see how it connects back to the main topic — that connection is what examiners reward.
Glossary
Try to recall each definition before you reveal it.
Quick check
Answer in your head first — then tap to check. No pressure.
Revision flashcards
Flip the card. Test yourself before the exam.
What is a LAN (Local Area Network)?
A network confined to a small geographical area, such as a single building or a university campus. It typically has high data transfer rates and is owned by an individual or organisation.
Key takeaways
Review these before you close the topic — retrieval beats re-reading.
- ✓
PAN (Personal Area Network): The smallest type of network, spanning just a few metres. It's used for connecting personal devices, often using wireless technologies like Bluetooth. For example, connecting a wireless headset to a smartphone.
- ✓
LAN (Local Area Network): Covers a limited area like a home, office, or school. Devices are connected via switches and cables (Ethernet) or wirelessly (WLAN - Wireless LAN). The organisation that owns the LAN also owns the networking equipment.
- ✓
WAN (Wide Area Network): Spans a large geographical area, connecting LANs together. The internet is the ultimate example of a WAN. WANs rely on infrastructure provided by telecommunications companies, such as fibre optic cables, satellite links, or microwave relays.
Practice — then mark it
The whole point: a real Cambridge question, marked mark-by-mark.
Test Your Knowledge on Networks
Test Your Knowledge on Networks
Extra simulations & links
PhET, GeoGebra and other curated tools — open in a new tab.
Frequently asked
Checkpoint
One marked question is worth ten re-reads — close the loop before you move on.
Reading it isn’t knowing it — prove it.
Before you move on: do Test Your Knowledge on Networks on paper, snap a photo, and get examiner-style feedback on exactly where you win and lose marks.