Functions and practical applications of network topologies
Describe the functions and practical applications of network topologies
In this lesson
- What a network topology is: nodes, links, hops and single points of failure
- How star, mesh and hybrid topologies are arranged
- How they compare for reliability, transmission speed, scalability, data collisions and cost
- Which topology suits a home, a small office or a large organisation
LearnWhat a topology is
A network topology is the arrangement of the devices (nodes) in a network and the links between them.
LearnStar, mesh and hybrid
LabBreak the network
Build each topology, then select a device, a switch or a cable to break it. Watch which devices can still reach each other, how many hops data needs, and how much cabling each design uses.
Select a device, a switch or a cable to break it; select it again to repair it. Switches outlined in orange are single points of failure.
- Cables / links
- 6
- Switches
- 1
- Ports used on busiest switch
- 6
- Most hops between two devices
- 2
- Single points of failure
- S1
All 15 pairs of devices can reach each other.
Every device has its own cable to the central switch. A modern switch gives each cable its own full-duplex link, so frames do not collide; an old hub shared one channel between all devices, so frames could collide.
Try at least three topologies and break something in each to complete this activity.
LearnComparing the topologies
| Star | Mesh | Hybrid (stars + meshed core) | |
|---|---|---|---|
| Reliability | A broken cable or device affects only that device, but if the central switch fails the whole network stops | Several paths, so data is rerouted around a failed link or node; a full mesh has no single point of failure | The core keeps working if one core link fails, but each edge switch is still critical for the devices attached to it |
| Transmission speed | Two hops between any two devices; each device has its own link to the switch; the switch can become a bottleneck | Full mesh: one hop on a dedicated link. Partial mesh: some data needs several hops | Fast within a star; traffic between parts crosses the core, which uses high-capacity links |
| Scalability | Easy: plug a new device into a free port, until the switch runs out of ports | Wired full mesh scales badly: every new node needs a link to every other node. Wireless mesh nodes join easily | Good: add a new star, or a new core switch, without changing the rest |
| Data collisions | None on wired links to a switch, because each device has its own full-duplex link. Wi-Fi devices around an access point share one radio channel, so they must take turns. Possible on any shared medium | None on wired point-to-point links. Wireless mesh nodes share radio channels, so they must take turns | Depends on the parts: switched stars and wired core links have no collisions |
| Cost | Low: one cable per device and one switch | High for wired full mesh (cables and ports grow very quickly); wireless mesh nodes cost more than simple access points | Higher: more switches and links, and more complex to design and manage |
A collision happens when two devices transmit on the same shared medium at the same time, so both transmissions are damaged and must be sent again.
CheckQuick check
An office of 20 computers is wired in a star around one switch. Which event stops all 20 computers communicating with each other?
LearnTopologies in practice
CheckWhich topology fits?
Choose the most suitable topology for each network.
- Six computers and a printer in a dentist's surgery
- Hundreds of temperature sensors spread across a large warehouse, with no cables
- A university with 12 buildings, each with its own switch
- Four core routers in a bank's data centre that must never lose contact
- A family home with a laptop, two phones and a smart TV, all near the router
- A government ministry with offices on 8 floors and a server room
ExamWorked exam answer
Outline one advantage of a wireless mesh system for a large house where one access point does not reach every room.
[2]ReviewMistakes examiners see
“A star is unreliable” is too vague. Say what fails: one cable or device affects only that device; the central switch affects everyone.
Mesh is not only wireless. The idea applies to any network where nodes have links to several other nodes.
A hybrid is not automatically free of single points of failure. Check each part of the design.
When asked to choose a topology, link each factor to the scenario: not just “more reliable”, but what keeps working when a named device fails.
Exam practiceExam-style questions
5 questions · 12 marks. Answer each one first, then mark it yourself against the markscheme. Your answers are saved in this browser only.
A college has seven buildings. The computers in each building are connected to a switch in that building, and the seven building switches are linked to each other. The old library building still uses a hub instead of a switch.
Calculate the number of links needed to connect the seven building switches in a full mesh.
The computer science building will add 40 computers next year, but its switch has only 8 free ports. Outline how the star design can be extended.
The college links the seven building switches in a partial mesh rather than a full mesh. Explain why.
Library users complain that the network becomes slow when many students use it at once, while other buildings with the same number of users do not. Explain why.
Describe what happens to the college network if the switch in the science building fails, compared with the failure of one cable between two building switches.
0 of 5 questions marked. Mark every question to see your total.
Exam-style questions written for Praxis IB in the format of the 2027 specimen papers. They are not IB past-paper questions.