The big idea: A topology is how the devices are connected to each other.
The shape decides what happens when something fails, how much cable it takes, and how easy it is to add the next device.
The five things to weigh: Reliability · speed · scalability · collisions · cost.
Every topology question is answered from these five. No shape wins on all of them.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
Each shape, and what happens when something in it fails. Step through all five.
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
Star
- Every device connects to one central switch
- Cost low — one cable each
- Scalability good — add a device, add a cable
- Collisions rare — the switch separates traffic
- Reliability the switch is a single point of failure
Mesh
- Every device connects to every other
- Cost high — links grow much faster than devices
- Scalability poor — a sixth device needs five new links
- Collisions none — each link is private to one pair
- Reliability very high — no single link matters
Hybrid
- Stars joined together, often by stronger links
- Cost moderate — mesh only where it earns its keep
- Scalability good — add a switch for a new section
- Reliability a switch failure costs one section, not all
- What almost every real office and campus actually uses
Why a star still wins so often: The switch is a single point of failure — but switches fail rarely, and the topology is cheap, fast and easy to extend.
Organisations that cannot accept that risk buy a second switch rather than abandon the shape.
Get feedback like a real examiner
Submit your answers and get instant feedback — what you did well, what's missing, and exactly what to write to score full marks.
A home or small office — star
A handful of devices, a tight budget, and no dedicated staff.
One switch, one cable each. If it fails, someone replaces it in an hour — which is an acceptable risk at this scale.
A bank's core links — mesh
Between a few critical sites, where an outage costs far more than cable does.
Multiple routes mean no single failure can disconnect anything. The poor scalability does not matter, because there are only a few sites.
A campus or corporation — hybrid
Stars in each building, joined by resilient links between them.
Cheap where devices sit, reliable where the traffic concentrates. This is why hybrid is what you actually find.
Full mesh does not scale: 5 devices need 10 links. 10 devices need 45. 20 devices need 190.
The links grow roughly with the square of the devices, which is why full mesh is reserved for a small number of critical points.
How this is tested — you must justify a topology from the five factors, not just name it. It comes up two ways:
Paper 1 Section A
- Describe or compare topologies, 3-5 marks
- Recommend one for a described organisation
- Explain what happens when a named component fails
Paper 1 Section B — case study
- Choose a topology for the case study's premises
- Justify it from their size, budget and uptime needs
The classic trap: Recommending mesh because it is the most reliable. Reliability is one factor of five — and mesh's cost and scalability rule it out for anything with more than a handful of nodes.
A hospital has three buildings, each with about forty computers. Patient monitoring must not be interrupted. Recommend a topology and justify it.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.