Networks, hardware and topologies
A network connects devices so they can share data and resources. You need to name the hardware, compare the layouts (topologies), and describe how the internet works at a basic level.
Part 1 of 3: Learn it
In short
- A LAN covers a small area and uses the owner's own hardware; a WAN covers a large area and uses hired lines.
- In a star topology every device connects to a central switch; in a mesh, devices connect to many others.
- The internet is a worldwide WAN; DNS turns web addresses into IP addresses.
Where this is in your specification
Spec points: AQA 3.5, OCR 1.3.1 and 1.3.2, Edexcel Topic 4
| Board | Topic: Networks and protocols |
|---|---|
| AQA 8525 | 3.5 |
| Edexcel 1CP2 | Topic 4 |
| OCR J277 | 1.3.1 and 1.3.2 |
| Eduqas C500 | 3 Networking and cybersecurity |
| Cambridge IGCSE 0478 | 2.1, 2.2, 3.4, 5.1, 5.2 |
LANs and WANs
A local area network (LAN) covers one site, such as a school or a home, and the hardware belongs to the organisation. A wide area network (WAN) connects LANs across large distances using infrastructure owned by telecoms companies. The internet is the biggest WAN.
Network hardware
| Device | Job |
|---|---|
| Network interface card (NIC) | lets a device connect to a network; has a unique MAC address |
| Switch | connects devices in a LAN and sends data only to the device it is addressed to |
| Router | sends data between networks, such as from a LAN to the internet |
| Wireless access point (WAP) | lets wireless devices join a wired network |
| Transmission media | copper (Ethernet) cable, fibre optic cable, or radio waves for wireless |
Topologies
| Star | Mesh | |
|---|---|---|
| Layout | every device has its own cable to a central switch | devices connect to many (full mesh: all) other devices |
| If one cable fails | only that device is affected | data takes another route |
| If the centre fails | the whole network stops | no single centre to fail |
| Cost | cheaper | more cabling or more wireless links |
Wired and wireless, and the internet
Wired connections are usually faster, more reliable and harder to intercept; wireless ones allow movement and need no cables, but suffer interference and must be encrypted.
Websites are stored on web servers. When you type a web address, a DNS server looks up the matching IP address so your device knows where to send its request. Hosting means storing a website on a server that is always connected to the internet.
What does a DNS server do?
Show the answer
It translates a domain name into the IP address of the server.
Part 2 of 3: See it worked
Worked examples
Example 1
A 2.5 GB file is sent over a connection of 100 megabits per second. Estimate the time taken, using 1 GB = 1000 MB.
- 2.5 GB = 2500 MB
- In bits: 2500 × 8 = 20 000 megabits
- Time = 20 000 ÷ 100
Answer: About 200 seconds.
Example 2
A hospital is choosing between a star and a full mesh network for its critical equipment. Recommend one, with a reason.
- In a star, a failure of the central switch stops every device
- In a mesh, data can be sent another way if one link fails
- For critical equipment, staying connected matters more than cost
Answer: A mesh, because there is no single point whose failure would stop the whole network.
Common mistakes
- Saying a router connects devices within a LAN. That is the switch; the router connects networks.
- Confusing the internet (the network) with the World Wide Web (the pages carried on it).
- Forgetting to multiply bytes by 8 to get bits in transfer time questions.
- Saying a star network fails if any cable breaks. Only the device on that cable is affected.
Give one advantage of a wired connection over wireless.
Show the answer
Any one of: faster, more reliable, less interference, harder to intercept.
Part 3 of 3: Test yourself
Check yourself
Answer each one in your head or on paper first, then open it to check.
What does a DNS server do?
It translates a domain name into the IP address of the server.
Give one advantage of a wired connection over wireless.
Any one of: faster, more reliable, less interference, harder to intercept.
What is the main weakness of a star topology?
If the central switch fails, the whole network stops working.
Jobs that use this
- Network engineer (öffnet einen neuen Tab)
- IT security co-ordinator (öffnet einen neuen Tab)
- Systems analyst (öffnet einen neuen Tab)
Each link opens the job profile on the National Careers Service (England). In the rest of the UK: My World of Work (Scotland), Careers Wales, nidirect careers (Northern Ireland).
Diese Lernzettel sind auf Englisch, weil sie britischen Prüfungslehrplänen folgen.
Full lessons and marked practice for this course are coming soon to Brainlag Learn. See courses