Simulic
English

Network hardware and transmission media – build a LAN and connect it to the Internet

Computer ScienceNetworks & the InternetAges 17–18

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Build a LAN with network interface cards (NICs), a switch, a router, a wireless access point and a modem that connects to an Internet service provider. Choose twisted pair or fibre-optic cable and 2.4 or 5 GHz Wi-Fi, then change the number of devices, cable length, distance to the access point, interference, encryption and Internet speed to see signal loss, link rates and each device's bandwidth. Animated packets show what every device does with the frame, including its MAC and IP addresses; cut cables to compare star and mesh layouts, and use the table to compare media and the security of wired and wireless networks.

Lesson: Network hardware (NIC, switch, router, wireless access point, modem) and transmission media (twisted pair, fibre optic, Wi-Fi); LAN and WAN; MAC and IP addresses; wired and wireless networks; star and mesh topologies

What it shows

Every device on a network needs a network interface card with a unique MAC address. A switch joins the devices of a LAN and forwards each frame only to the port of its destination MAC address, a wireless access point joins Wi-Fi devices to the cabled network, and a router reads IP addresses to send packets on to other networks; a modem links the router to the Internet service provider's line. Twisted pair loses signal quickly and is limited to 100 m per run, fibre carries light over kilometres without electrical interference, and Wi-Fi is convenient but shared, shorter-range and readable outside the building unless encrypted.

How to use

Tick or untick Switch, Router, Access point and Modem to see what each one is for. Set the numbers of wired PCs and Wi-Fi devices, the cable type and length, the Wi-Fi band, distance, interference, encryption and Internet speed. Click a device to make it the sender, then press Send file in LAN or Open web page and watch the packet and the frame header hop by hop. Click a cable to cut it and compare Star with Mesh. The table and the graph show signal, link rate and throughput.

Parameters you can change

  • LAN topology Star (one switch), Mesh (three cross-linked switches)
  • Wired PCs 0–8 PCs
  • Wi-Fi devices 0–12 devices
  • Cable type Twisted pair (Cat 6), Fibre optic (single-mode)
  • Cable length to each PC 1–2000 m
  • Wi-Fi band 5 GHz, 2.4 GHz
  • Distance to the access point 1–60 m
  • Interference None, Low, Medium, High
  • Wi-Fi encryption None (open network), WPA2, WPA3
  • Internet connection speed 10–1000 Mbit/s
  • Switch fitted
  • Router fitted
  • Wireless access point fitted
  • Modem fitted

Questions to explore

  1. Why does a twisted-pair cable longer than 100 m need a switch in the middle or a change to fibre?
  2. Which addresses in the frame change at the router, and which stay the same all the way to the server?
  3. Why can an outsider in the street receive Wi-Fi frames, and what stops them reading the data?

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