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 (opens a new tab)
- IT security co-ordinator (opens a new tab)
- Systems analyst (opens a new 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).
Full lessons and marked practice for this course are coming soon to Brainlag Learn. See courses