What is a Network?
A computer network is two or more computers or devices connected together to share resources, data, and services. Networks can be wired (using cables) or wireless.
Types of Network
LAN (Local Area Network)
A LAN covers a small geographical area — a single building, school, office, or home. The hardware (cables, routers, switches) is typically owned by the organisation.
- High data transfer speeds (up to 10 Gbps on modern systems)
- Generally more secure — limited physical access
- Low cost to set up and maintain
- Example: a school network, a home network
PAN (Personal Area Network)
A PAN covers a very small area around an individual, typically within a few metres. PANs connect personal devices to each other.
- Examples: connecting a smartphone to wireless earbuds via Bluetooth, linking a smartwatch to a phone, a laptop connecting to a wireless mouse
- Typically uses Bluetooth or Wi-Fi Direct
- Very short range (Bluetooth: ~10 metres)
- Low power consumption
WAN (Wide Area Network)
A WAN covers a large geographical area — cities, countries, or globally. It connects multiple LANs together. WANs often use infrastructure owned by telecom companies (leased lines, satellites, fibre).
- Slower than LANs due to greater distances and shared infrastructure
- More expensive — relies on third-party infrastructure
- Less secure — data travels over public infrastructure
- Example: the internet is the world's largest WAN
Network Models
Client-Server Network
A central server provides services and resources. Clients request and receive those resources. The server manages security, user accounts, and data storage centrally.
- Centralised management — easy to update and secure
- If the server fails, clients lose access
- Used in schools, businesses, and most large organisations
Peer-to-Peer (P2P) Network
All computers (peers) have equal status. Each can act as both client and server — sharing resources directly with other peers. No central server.
- Easy to set up, low cost
- Less secure — no central control
- Harder to manage as the network grows
- Suitable for small home networks or file sharing
Network Hardware
| Device | Purpose |
|---|
| Router | Connects a LAN to the internet (WAN); routes data packets between networks using IP addresses |
| Switch | Connects devices within a LAN; sends data only to the intended device (using MAC addresses) |
| Hub | Like a switch but sends data to ALL connected devices — less efficient, rarely used today |
| WAP (Wireless Access Point) | Enables devices to connect to the network wirelessly (Wi-Fi) |
| NIC (Network Interface Card) | Hardware in a device that allows it to connect to a network (wired or wireless) |
| Modem | Converts digital signals to analogue (and back) for transmission over telephone lines |
| Transmission media | Copper cables, fibre optic cables, Wi-Fi radio waves, Bluetooth |
📝 Exam Tip: Know the difference between a hub and a switch. A hub sends data to all devices (inefficient, less secure). A switch sends data only to the intended recipient. In the exam, always prefer a switch for efficiency and security in a LAN.
⚠️ Common Mistakes
- Saying a WAN is always the internet — the internet is a WAN but not all WANs are the internet (e.g. a company's private WAN connecting offices)
- Confusing client-server with peer-to-peer — in client-server, a dedicated server controls resources; in P2P, all devices are equal
- Saying a hub is the same as a switch — a hub broadcasts to everyone; a switch is targeted