Network Types
LAN — Local Area Network
A LAN covers a small geographical area (e.g. a school, office, or home). Hardware is owned by the organisation. Connected using cables (Ethernet) or Wi-Fi.
- Small geographic area (single site)
- High data transfer speeds
- Hardware owned and maintained by the user
- Example: school network, home network
WAN — Wide Area Network
A WAN covers a large geographical area, connecting multiple LANs. Uses third-party telecoms infrastructure (leased lines, internet). The internet is the world's largest WAN.
- Large geographical area (cities, countries, worldwide)
- Lower speeds than LAN (depends on infrastructure)
- Infrastructure leased from third parties
- Example: internet, a company's network across multiple countries
| Feature | LAN | WAN |
|---|
| Area | Small (single site) | Large (multi-site/global) |
| Ownership | User organisation | Third-party / leased |
| Speed | High | Generally lower |
| Cost | Lower initial cost | Ongoing leased costs |
Network Topologies
A topology describes the physical or logical arrangement of devices in a network.
Star Topology
All devices connect to a central switch or hub. Most common in modern LANs.
- Advantages: Failure of one device doesn't affect others; easy to add/remove devices; easy fault diagnosis
- Disadvantages: Central switch failure brings down entire network; more cable required; switch is expensive
Bus Topology
All devices connect to a single shared cable (backbone) with terminators at each end.
- Advantages: Cheap and easy to install; less cabling needed
- Disadvantages: Backbone failure brings down entire network; collisions as devices compete for the cable; performance degrades with more devices; difficult to fault-find
Mesh Topology (extension)
Devices connect to multiple other devices. Common in wireless networks and the internet.
- Fully meshed: every device connects to every other — very resilient but expensive
- Partially meshed: some redundant paths — compromise between cost and resilience
- Advantages: Highly resilient, many redundant paths
- Disadvantages: Very expensive; complex to configure
Exam tip: Cambridge most commonly tests star vs bus. Know the key trade-offs. Star is more reliable; bus is cheaper. If the question mentions a switch, it's star topology. If it mentions a backbone cable, it's bus.
⚠️ Common Mistakes
- Saying a bus network is fast — collisions make it slow with many devices
- Confusing "hub" and "switch" — a hub broadcasts to all; a switch sends only to the intended device
- Saying a star network fails if one computer breaks — it's only the central switch failure that brings it all down