Network topology describes how devices in a network are physically or logically connected to each other. Star, mesh and bus topologies all appear regularly in GCSE Computer Science exams — you need to be able to draw them, describe how data travels and compare their advantages and disadvantages.
All devices connect to a central switch. The switch manages traffic — it sends data only to the intended recipient.
✓ Advantages
• One cable fail = only one device affected
• Easy to add new devices
• Easy to identify faults
• Switch manages traffic efficiently
✗ Disadvantages
• If the central switch fails, entire network goes down
• More cable needed than bus
• Switch is a single point of failure
Every device connects directly to every other device. Data can travel via multiple paths.
✓ Advantages
• No single point of failure
• Data can take alternative routes if one link fails
• Very reliable and resilient
✗ Disadvantages
• Very expensive — many cables required
• Complex to install and manage
• Impractical for large networks
All devices share a single cable (the bus). Data is broadcast to all devices; only the intended recipient accepts it.
✓ Advantages
• Simple and cheap to set up
• Uses very little cable
✗ Disadvantages
• A break in the bus cable = whole network fails
• Only one device can transmit at a time — collisions possible
• Performance degrades as more devices added
Try these before expanding the hints. Write your answer, then compare.
A school has 30 computers in a classroom all connected to a central switch. State what type of network topology this is and give one advantage of this topology.
Mark scheme hint: Star topology [1]. Advantage: if one cable fails, only that one device is disconnected — the rest of the network continues to work [1]. OR: easy to add new devices [1]. OR: easy to identify faults [1].
Compare the star and mesh network topologies. Your answer should include one similarity and one difference.
Mark scheme hint: Similarity: both connect multiple devices in a network [1]; OR both can be used for LANs [1]. Difference: star has a single central switch (potential failure point) whereas mesh has no central device and multiple paths between devices [1].
Explain one disadvantage of a mesh topology compared to a star topology.
Mark scheme hint: A mesh topology requires many more physical cables — each device must connect directly to every other device [1], making it much more expensive to install and maintain than a star topology where only one cable per device is needed [1].
State the difference between a LAN and a WAN.
Mark scheme hint: A LAN covers a small geographical area such as one building or site [1], whereas a WAN spans a large geographical area such as multiple cities or countries [1]. A LAN is typically owned by one organisation; a WAN uses infrastructure owned by multiple providers [1].
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Question Bank →"Star topology is better than mesh" — too vague, no marks.
"Star topology is cheaper to install and easier to manage because only one cable per device is needed. Mesh topology is more reliable because there is no single point of failure and data can take alternative routes if one link fails." Choose based on the scenario.
Saying "if the cable breaks in a star topology, the whole network goes down".
If ONE CABLE breaks in a star topology, only that one device loses connection. If the SWITCH fails, the whole network goes down. These are different — the cable and the switch are not the same thing.
Confusing a switch with a router.
A switch connects devices WITHIN a network (LAN) and directs data to the correct device. A router connects two DIFFERENT networks (e.g. your home LAN to the internet). A switch manages local traffic; a router routes traffic between networks.
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In a star topology, every device connects to a central switch or hub. If the switch fails, all devices lose connectivity — but a single cable failure only affects one device. In a mesh topology, every device connects directly to every other device. There is no single point of failure and data can take multiple routes, but it requires many cables and is expensive to install.
Star topology is dominant because: easy to add new devices (just plug in to the switch); a failure in one cable only affects that one device; easy to diagnose faults; the central switch can manage traffic efficiently. The main downside is that if the central switch fails, the whole network goes down.
A LAN (Local Area Network) covers a small geographical area — typically one building or site — and the hardware is usually owned and managed by one organisation. A WAN (Wide Area Network) spans a large geographical area, often connecting multiple LANs across cities or countries. The internet is the largest WAN. WANs typically use infrastructure leased from telecommunications providers.
A switch is the key hardware — it connects devices in a star topology and manages data traffic by sending packets only to the intended recipient device (unlike a hub which broadcasts to all). A router connects one network to another (e.g. a home network to the internet). A WAP (Wireless Access Point) allows wireless devices to connect to a wired network.