Networks: Types and Topologies
What a network is
A network is two or more devices connected together so they can communicate and share resources (files, printers, an internet connection). You need to know the types of network, common topologies, and the hardware and factors involved.
LAN vs WAN
| LAN (Local Area Network) | WAN (Wide Area Network) | |
|---|---|---|
| Area covered | Small – one site (home, school, office) | Large – towns, countries, the world |
| Owned by | The organisation that uses it | Often uses third-party infrastructure (e.g. telecom lines) |
| Example | School network | The internet (the biggest WAN) |
Wired vs wireless
- Wired (usually Ethernet cable): faster, more reliable, more secure, but less convenient (needs cables).
- Wireless (Wi-Fi): convenient, no cables, lets devices move around, but generally slower, less secure and can suffer interference/range issues.
Factors affecting network performance
- Bandwidth – the amount of data that can be carried per second. More bandwidth = better performance. Bandwidth is shared between users, so more users can slow it down.
- Wired vs wireless – wired is usually faster/more reliable.
- Interference and distance – weaken wireless signals.
- Number of devices/users and number of collisions of data.
Network topologies
The topology is the layout — how devices are connected.
Star topology
- Every device connects to a central switch (or hub).
- Advantages: if one cable/device fails, the others keep working; easy to add devices; good performance (few collisions).
- Disadvantages: needs lots of cable; if the central switch fails, the whole network goes down.
Mesh topology
- Every device connects to many/all other devices, so data has multiple possible routes.
- Advantages: very reliable — if one path fails, data reroutes; no single point of failure.
- Disadvantages: expensive and complex (lots of connections). Common in wireless networks (e.g. smart devices).
Common network hardware
- NIC (Network Interface Card) – lets a device connect to a network.
- Switch – connects devices on a LAN and sends data only to the intended device.
- Router – connects different networks together and directs data between them (e.g. your home network to the internet).
- WAP (Wireless Access Point) – lets devices connect wirelessly.
- Transmission media – Ethernet cable, fibre-optic cable, or radio waves (Wi-Fi).
Worked example
A school wants a layout where one broken cable won't take down the whole network and devices are easy to add. Which topology?
- Star — each device has its own link to the central switch, so one failure is isolated. ✓
Common mistakes
- Confusing a switch (within one LAN) with a router (between networks).
- Saying the internet is a LAN — it's the largest WAN.
- Forgetting that in a star topology the central switch is a single point of failure.
Exam tips
- For "which topology" questions, justify with reliability, cost and single points of failure.
- Learn one clear advantage and disadvantage for star and mesh.
- Remember bandwidth is shared — a common reason a network "slows down when busy".
Key facts to remember
- LAN = small area, owned by one org; WAN = large area, third-party infrastructure (the internet).
- Star = devices to a central switch (one failure isolated, but switch is a single point of failure); mesh = many routes, very reliable.
- Key hardware: NIC, switch, router, WAP; performance depends mainly on bandwidth (shared) and wired vs wireless.