How are computers connected together, and in what shapes?
Understand what a network is, the difference between a LAN and a WAN, and the star and bus (mesh) network topologies.
A focused answer to AQA GCSE Computer Science 3.5.1, covering what a network is, the difference between a LAN and a WAN, and the star and bus network topologies.
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What this dot point is asking
AQA wants you to explain what a network is, distinguish a LAN from a WAN, and describe the star and bus network topologies with their advantages and disadvantages.
What a network is
LAN and WAN
The two distinguishing features the exam wants are geographic scale and ownership of the infrastructure. A WAN is not simply a large LAN: the defining point is that it spans a wide area using infrastructure the organisation does not own, often connecting several LANs together.
Star topology
A star is reliable, because if one cable fails only that one device is cut off while the rest keep working, and it performs well because the switch sends each message only to its recipient, reducing collisions. The trade-offs are that it needs more cabling (one cable per device) and the whole network depends on the central switch, so if the switch fails the network goes down.
Bus topology
A bus uses less cabling and is cheap and simple to set up, but because the cable is shared, only one device can transmit at a time, so it can become congested as more devices are added, and if the backbone cable fails the whole network goes down.
The hardware that makes a network
A network needs more than cables. A network interface card (NIC) gives each device a connection and a unique MAC address. A switch connects devices in a star and sends each message only to its destination. A router connects different networks together, for example a home LAN to the internet (a WAN), choosing the path packets take. A wireless access point lets devices join without cables. Understanding these roles explains why a star topology depends on its central switch and why connecting a LAN to a WAN needs a router.
Try this
Q1. State one difference between a LAN and a WAN. [2 marks]
- Cue. A LAN covers a small area and is usually owned by one organisation; a WAN covers a large area using third-party infrastructure.
Q2. Give one advantage of a star topology. [1 mark]
- Cue. If one cable fails, only that device is affected; the rest of the network keeps working.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20184 marksExplain the difference between a LAN and a WAN, referring to geographic area and ownership of the infrastructure, and give one example of each.Show worked answer →
A LAN (local area network) covers a small geographic area such as a single building or site, and the hardware and cabling are usually owned by the one organisation that runs it; an example is a school network. A WAN (wide area network) covers a large geographic area such as a country or the whole world, and it uses infrastructure owned by third parties such as telecoms companies; the internet is the largest example.
Markers reward the area contrast (small site versus large geographic spread), the ownership contrast (one organisation versus third-party infrastructure), and a valid example of each.
AQA 20215 marksCompare a star topology with a bus topology. Give one advantage and one disadvantage of each, and recommend which is more suitable for a busy office that cannot tolerate the whole network failing.Show worked answer →
Star: each device has its own cable to a central switch. Advantage: if one cable fails only that device is affected, so it is reliable; disadvantage: it needs more cabling and depends on the central switch. Bus: all devices share one backbone cable. Advantage: cheap and uses little cabling; disadvantage: the shared cable can become congested and if the backbone fails the whole network goes down.
For a busy office that cannot tolerate total failure, a star is more suitable: a single cable fault affects only one device, and the higher cabling cost is worth the reliability.
Markers reward one advantage and one disadvantage of each plus a justified recommendation tied to reliability.
Related dot points
- Compare wired and wireless connectivity, understand how Wi-Fi works, and the role of encryption in wireless networks.
A focused answer to AQA GCSE Computer Science 3.5.2, covering the comparison of wired and wireless connectivity, how Wi-Fi works, and the role of encryption in wireless networks.
- Understand the purpose of network protocols, the common protocols and ports, and the four-layer TCP/IP model and why layering is used.
A focused answer to AQA GCSE Computer Science 3.5.3, covering the purpose of network protocols, the common protocols and ports, and the four-layer TCP/IP model and why layering is used.
- Understand the methods used to keep a network secure, including authentication, encryption, firewalls and MAC address filtering.
A focused answer to AQA GCSE Computer Science 3.5.4, covering the methods used to keep a network secure, including authentication, encryption, firewalls and MAC address filtering.
- Understand the difference between hardware and software, and the relationship between them in a computer system.
A focused answer to AQA GCSE Computer Science 3.4.1, covering the difference between hardware and software and the relationship between them in a computer system.
Sources & how we know this
- AQA GCSE Computer Science (8525) specification — AQA (2020)