Network Builder
Switches inside, routers in between.
Your mission
Two campuses, one Internet. Find out what switches, routers and cables really do, then wire up a computer lab yourself: print, share files and open a website. Then play network doctor and work out what broke when a lab stops working.
Explore
Tap the devices, the cables and the dotted LAN boxes to see what each part of the network does.
Everything with a dashed circle can be tapped: devices, the round buttons on the cables, and the dotted LAN boxes.
Two university campuses, each with its own network, joined across the Internet. Tap the switches, the routers, the Internet and the cables to see what each part does. The data moves as you tap.
0 of 7 discoveries made
Experiment
Plug in the cables of a computer lab, then print, share a file and open a website. Unplug things to see what breaks.
Tap a glowing plug to connect a cable. Tap the small ✕ on a cable to unplug it again.
Lab technician's jobs
Try each one. They tick themselves off.
0 of 6 experiments done
Challenge
Six repair jobs: find the broken device, choose a switch or a router, sort LANs from WANs and match each medium to its signal.
Technician's notes
- Switch: connects devices inside one LAN
- Router: connects different networks (LAN ↔ Internet)
- LAN: a limited area · WAN: large distances
- The Internet is a network of networks
- Copper → electrical signals · Fibre → light · Wireless → electromagnetic waves
- A LAN keeps working when the Internet is down
Finish all 6 jobs to finish this stage.
Understand
Here is what the networks were showing you, in the words you need for the exam.
What is a computer network?
A computer network is a group of devices that can communicate and exchange data: laptops, phones, servers, printers. Networks can use wired connections (cables) and wireless connections. Networks come in different sizes:
| Network | Covers |
|---|---|
| LANLocal Area Network | A limited geographical areaA home, a computer laboratory, an office, a university building |
| WANWide Area Network | Larger geographical distancesCampuses in different cities or countries; the Internet |
The Internet is a network of networks
The Internet is not one giant computer. It connects many computers and networks around the world, joined by routers and Internet service providers. It is the best-known example of a WAN.
It grew fast: in 1969 ARPANET connected four research sites; in the 1980s networks expanded rapidly; in the 1990s the World Wide Web brought in the public; today billions of people and devices are connected.
Switch ≠ router
A switch connects devices within a LAN and forwards data to the correct device (PC ↔ PC ↔ printer). Local devices can still communicate without Internet access.
A router connects different networks and forwards data between them (LAN ↔ Internet). The box at home that links your home network to the Internet is a router.
Switch = inside the network. Router = between networks.
What carries the data?
| Medium | Carries data as |
|---|---|
| CopperEthernet (twisted pair) and coaxial cables | Electrical signals |
| Optical fibreFibre optic cables between buildings, cities and countries | Light signals through glass fibres |
| WirelessWi-Fi, Bluetooth, cellular, satellite, microwave | Electromagnetic waves |
Different physical media, same goal: move bits from one device to another.
Hong Kong's connection to fibre optics
Sir Charles K. Kao (1933–2018) pioneered the use of high-purity optical fibre for long-distance communication. He received the 2009 Nobel Prize in Physics and was a former Vice-Chancellor of CUHK. A large share of the world's long-distance Internet traffic now travels as light through optical fibre.
Exam tip
Don't mix up the two boxes: a switch connects devices inside one LAN, and a router connects different networks (for example your LAN and the Internet). If the Internet goes down, devices on the same LAN can still communicate through the switch. For media questions, match the signal: copper → electrical signals, fibre → light signals, wireless → electromagnetic waves. And the Internet is a network of networks, the best-known WAN.