Network topologies GCSE computer science questions usually come down to two layouts: star and mesh. A star topology connects every device to one central switch; a mesh topology connects devices directly to several (or all) other devices. Examiners want you to compare their reliability, cost, and how each copes with a failed connection.
What is a network topology?
A network topology is the arrangement of devices, cables, and connections in a network — essentially, the map of how everything is wired together. It describes the physical or logical layout, not the data itself. GCSE specifications (AQA, OCR, and Pearson Edexcel) all require you to compare topologies and explain their trade-offs, because the layout a school or business chooses affects cost, speed, and resilience.
The two topologies most commonly examined at GCSE are star and mesh. Bus and ring topologies appear on some historical specifications but are largely replaced by star and mesh in current courses, since almost all modern wired networks use a star arrangement built around a switch.
What is a star topology?
In a star topology, every device (computer, printer, server) connects with its own individual cable to a central device — usually a switch — rather than to each other. Data sent from one device travels first to the switch, which then forwards it to the correct destination.
Most school and office networks use a star topology because it is straightforward to install, monitor, and expand.
Advantages of star topology:
- If one cable or device fails, only that device loses its connection — the rest of the network keeps working.
- New devices are easy to add: just run a new cable to the switch.
- The central switch can monitor traffic and manage data efficiently, reducing collisions.
- Performance stays consistent even as more devices join, provided the switch has spare ports and bandwidth.
Disadvantages of star topology:
- If the central switch fails, the entire network goes down — this is the topology's single point of failure.
- It needs more cabling than some other layouts, since every device needs its own direct run back to the switch.
- Network performance depends on the capability of the central switch.
What is a mesh topology?
In a mesh topology, devices connect directly to several other devices rather than to one central point. In a full mesh, every device connects to every other device. In a partial mesh, only some devices have multiple direct connections, while others connect through an intermediate device.
Mesh topologies are common in situations where reliability matters more than cost — wide area networks (WANs) linking data centres, wireless mesh networks in large buildings, and parts of the internet's core infrastructure.
Advantages of mesh topology:
- No single point of failure: if one connection or device breaks, data can usually be rerouted through another path.
- High reliability and fault tolerance — this is the main reason organisations choose mesh over star for critical infrastructure.
- Multiple paths can improve performance under heavy traffic, since data is not forced through one central bottleneck.
Disadvantages of mesh topology:
- Expensive: a full mesh needs far more cabling (and network ports) than a star topology with the same number of devices.
- Complex to install, configure, and maintain, especially as the network grows.
- Adding a new device to a full mesh means wiring it to every existing device, which becomes impractical past a handful of nodes.
Star topology vs mesh topology: side-by-side comparison
| Feature | Star topology | Mesh topology |
|---|---|---|
| Wiring | Every device to one central switch | Devices connect directly to several/all other devices |
| Single point of failure | Yes — the central switch | No — multiple paths for data |
| Cost of cabling | Lower | Much higher |
| Ease of adding devices | Easy — one new cable to the switch | Hard — may need cables to every other device |
| Fault tolerance | Low (if switch fails, network fails) | High (data reroutes around a failure) |
| Typical use | School and office LANs | WAN backbones, critical infrastructure |
| Installation complexity | Simple | Complex |
How much cabling does each topology need? A worked example
Cabling cost is a common exam calculation, so it helps to work through the numbers.
Star topology with 6 devices: each device needs exactly one cable to the central switch, so the network needs 6 cables.
Full mesh topology with 6 devices: every device must connect directly to every other device. The number of cables needed is given by the formula for connecting $n$ devices:
$$\text{cables} = \frac{n(n-1)}{2}$$
For $n = 6$:
$$\frac{6 \times 5}{2} = \frac{30}{2} = 15 \text{ cables}$$
That is 15 cables for a full mesh compared with 6 for a star — more than double, for the same six devices. Scale this up to a 20-device office and the star topology still needs only 20 cables, while a full mesh would need $\frac{20 \times 19}{2} = 190$ cables. This is exactly why full mesh topologies are reserved for small, critical networks rather than everyday office LANs.
Which topology should you choose in an exam question?
GCSE questions often present a scenario and ask you to recommend a topology with justification. Use this checklist:
- Identify the priority. Is the question emphasising cost, reliability, or ease of expansion?
- Match the topology to the priority. Choose star for low cost and simple management; choose mesh for maximum reliability where downtime is unacceptable.
- Justify with a specific advantage AND disadvantage. Mark schemes reward answers that explain a trade-off, not just a definition — for example, "star is cheaper to install but the whole network fails if the switch breaks."
- Reference the scenario. A school computer suite, a hospital's critical systems, and a small business office each have different priorities — tie your answer to the context given.
Frequently asked questions
What is a star network?
A star network is a topology where every device connects with its own cable to one central switch, rather than to each other directly. All data passes through the switch, which forwards it to the correct device. It is the most common topology in school and office networks because it is affordable, easy to expand, and keeps most of the network running even if one device's cable fails.
What are the main advantages of a star topology?
The main advantages are that a single cable or device failure does not bring down the rest of the network, new devices are simple to add by running one cable to the switch, and the central switch can manage traffic to reduce data collisions. These advantages explain why star is the default choice for most GCSE-level network scenarios.
Why is mesh topology more expensive than star topology?
A mesh topology needs far more cabling because devices connect directly to several (or all) other devices rather than to one central switch. A full mesh of $n$ devices needs $\frac{n(n-1)}{2}$ cables, which grows much faster than the $n$ cables a star topology needs for the same number of devices. This extra cabling and the extra network ports required make mesh topologies significantly more expensive to install.
Which topology has no single point of failure?
Mesh topology has no single point of failure, because devices have multiple paths to reach each other — if one connection breaks, data can be rerouted through an alternative path. Star topology, by contrast, relies entirely on its central switch; if that switch fails, every device loses its connection to the rest of the network at once.
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