How to use it. Choose a device in the Devices panel, then tap the canvas to place it (or drag it on). Pick Cable or Wireless and tap two devices to connect them; drag a device to move it; Delete removes a device or a connection. Each connection says whether it works and why. Check my network marks the task's requirements, and Send a message follows a message from one device to another, showing what each device on the way does with it. Work through the five tasks (the review at the end lists your mistakes, with the right answers), or choose Free build.
The devices
- Every device has a network interface card (NIC), with a MAC address: a unique number given to it when it was made, written as six pairs of hexadecimal digits (such as 3C-52-82-1A-0B-F0). It doesn't change.
- An IP address is given to a device by the network it joins (such as 192.168.1.10), so it changes when the device moves to another network. IPv4 addresses are 32 bits, written as four numbers from 0 to 255; IPv6 addresses are 128 bits.
- A switch connects the devices of a LAN. It learns which MAC address is on which of its ports and sends each frame only to the device it is addressed to. (A hub sends everything to every device, which wastes bandwidth and is less secure.)
- A router joins networks: a LAN to the internet, or one LAN to another. It reads each packet's destination IP address, looks it up in its routing table and sends it on towards that network.
- A wireless access point (WAP) lets wireless devices join a wired LAN: it is cabled to a switch and sends and receives WiFi radio signals.
- A modem (modulator-demodulator) converts digital signals into analogue signals to travel over a telephone or cable line, and back again.
In this simulator a router only joins networks, so a LAN's computers plug into a switch. A home "router" box is several devices in one case: a router, a small switch, a WAP and often a modem.
LAN, WLAN and WAN
- A local area network (LAN) covers a small area, such as one building or school, using cables and switches.
- A wireless LAN (WLAN) is a LAN whose devices connect by radio (WiFi) through wireless access points.
- A wide area network (WAN) covers a large area, such as a country, by joining LANs; the routers at each site are linked over the internet, a leased line or a VPN. The internet is the largest WAN.
Wired or wireless?
- Cables are faster and more reliable (less interference), and harder to eavesdrop on, but cost more to install, and devices can't move about freely; cables can be a trip hazard.
- Wireless lets devices move (laptops, tablets, phones) and is easy to add to, with no cabling cost, but it is slower, its signal is weakened by walls and distance and suffers interference, and anyone in range can try to intercept it, so it must be encrypted (WPA2/WPA3) and password protected.
- WiFi and Bluetooth both use radio waves. WiFi has a longer range and is faster, for joining a network; Bluetooth is short-range and low-power, for pairing two devices (a phone and headphones).
Cloud computing
Storing files and running software on servers owned by a provider, reached over the internet, rather than on your own computers. For: files can be reached from any device, anywhere; no need to buy and maintain your own servers and storage; the provider backs it up; it is easy to add storage. Against: it needs a fast, reliable internet connection; your data is held by another company (security and privacy, data protection laws); there are ongoing fees; and if the provider fails, your data may be lost or unreachable.
Common exam mistakes: saying a switch uses IP addresses (it uses MAC addresses) or that a router connects the computers in a LAN (it joins networks); confusing a router with a modem; saying a MAC address changes when a device moves (its IP address does); calling a WAP a router; treating the internet and the World Wide Web as the same thing; giving "faster" or "cheaper" without saying faster or cheaper than what.
For AS Level (9626). Also know a bridge (joins two LANs that use the same protocol), a repeater (boosts a signal over a long cable), a gateway (joins networks that use different protocols), and cable types: twisted pair (Ethernet), coaxial and fibre optic (fastest, longest distances, no electrical interference).
Objective: Cambridge IGCSE ICT (0417) section 4, networks: network devices (NIC, MAC and IP addresses, routers, switches, hubs, WAPs, modems), WiFi and Bluetooth, cloud computing, and LAN, WLAN and WAN; Cambridge International AS Level IT (9626), using networks: network types and devices, and wired and wireless connections.
Where this fits
- AQA: AQA A Level Computer Science (7517)
- Cambridge: Cambridge IGCSE Information and Communication Technology (0417); Cambridge IGCSE Computer Science (0478); Cambridge A Level Computer Science (9618); Cambridge AS Level Computer Science (9618); Cambridge A Level Information Technology (9626) Goes beyond Cambridge IGCSE Computer Science (0478): Switches, WAPs, modems and LAN/WLAN/WAN go beyond 0478 3.4.
- IB: IB Computer Science HL; IB Computer Science SL; IB Digital Society HL; IB Digital Society SL
- NCEA Level 2 Digital Technologies: 91895 Use advanced techniques to develop a network; 91895 Use advanced techniques to develop a network
- Pearson Edexcel International: Edexcel International GCSE Computer Science (4CP0); Edexcel International GCSE ICT (4IT1); Edexcel International A Level Information Technology
- USDP: USDP Computer Science
