A computer network connects two or more computers so they can share data, files, printers and an Internet connection. This chapter covers how networks are built and organised.
1Why networks & the devices
Networks let computers share resources (files, printers, Internet), communicate (email, chat) and save money (one printer for many PCs). The hardware that builds a network:
| Device | Job |
|---|---|
| NIC (Network Interface Card) | Connects a computer to a network (its network "door") |
| Hub | Joins devices; sends data to ALL of them (basic, less efficient) |
| Switch | Joins devices; sends data only to the RIGHT one (smarter than a hub) |
| Router | Connects different networks; directs data between them (e.g. your LAN to the Internet) |
| Modem | Converts digital ↔ analog signals so data can travel over phone/cable lines |
Key difference: a hub sends data to everyone; a switch sends it only to the intended device — so a switch is faster and more secure.
Key points
- Networks share resources (files, printers, Internet) and let computers communicate.
- NIC connects a PC to a network; a hub sends data to all devices, a switch only to the right one.
- A router connects different networks (LAN↔Internet); a modem converts digital↔analog signals.
2Types & topologies
Networks are classified by size:
| Type | Covers |
|---|---|
| PAN | A few metres (around one person — Bluetooth) |
| LAN | A building/campus (a school lab) |
| MAN | A city |
| WAN | Countries/the world (the Internet) |
Topology = the shape of the network
| Topology | Arrangement |
|---|---|
| Bus | All devices on one main cable (backbone) |
| Star | All devices connect to a central hub/switch (most common) |
| Ring | Devices in a closed loop; data travels around it |
| Mesh | Every device linked to every other (very reliable) |
| Tree | A hierarchy — like several stars joined to a backbone |
Key points
- By size: PAN (person) → LAN (building) → MAN (city) → WAN (the Internet).
- Topology is the network's shape: bus (one cable), star (central hub — most common), ring (loop), mesh (all-to-all), tree (hierarchy).
- Star is the most common; mesh is the most reliable but uses the most cable.
3Transmission media & protocols
Data travels over transmission media — wired or wireless:
| Wired (cables) | Wireless (no cables) |
|---|---|
| Twisted pair (Ethernet/LAN cable) | Infrared (TV remote, short range) |
| Coaxial cable (TV/cable) | Bluetooth (short range, devices) |
| Fibre optic (very fast, uses light) | Wi-Fi (a building) / WiMAX (a city) |
Protocols
A protocol is a set of rules for communication:
- HTTP — transfers web pages.
- FTP — transfers files to/from a server.
- TCP/IP — the core suite that packetises and reliably delivers data across the Internet.
Key points
- Wired media: twisted pair, coaxial, and fibre optic (fastest, uses light).
- Wireless media: infrared, Bluetooth (short range), Wi-Fi (building), WiMAX (city).
- Protocols are rules: HTTP (web pages), FTP (files), TCP/IP (the core Internet suite).
★ Practical: map a network
Think about your school or home network:
- Name the device that gives your computer Internet (router/modem).
- Say whether your network is a LAN, MAN or WAN.
- Which topology does a setup with all PCs connected to one switch use?
- Give one wired and one wireless transmission medium it uses.
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