Network Topologies
What Is Network Topology?
Network topology is the physical or logical arrangement of devices and connections within a network. The choice of topology affects cost, reliability, performance and security.
Bus Topology
All devices connect to a single central backbone cable. Data travels along the backbone to all devices, and each device checks if the data is addressed to it.
Device, Device, Device, Device, Device
│ Backbone │
| Advantages | Disadvantages |
|---|---|
| Simple and cheap to set up | Backbone = single point of failure, if it breaks, entire network fails |
| Easy to extend | Slow, all devices share the same cable |
| Less cabling | Not secure, all devices receive all data |
Seen in: Some residential zones, older installations.
Star Topology
All devices connect to a central switch (or hub). Each device has its own dedicated connection.
Device
│
Device──Switch──Device
│
Device
| Advantages | Disadvantages |
|---|---|
| One failed connection = only that device affected | Central switch = single point of failure for whole network |
| Secure, switch sends data only to intended device | More cabling than bus |
| Easy to add devices | |
| Good performance |
Seen in: Schools, offices, most modern wired LANs.
Switch vs Hub
A switch sends data only to the intended device. A hub broadcasts to all devices. Switches are more secure and efficient.
Mesh Topology
Devices connect directly to multiple other devices, providing redundant paths.
Full Mesh
Every device connects to every other device.
| Advantages | Disadvantages |
|---|---|
| No single point of failure | Very expensive, large amounts of cabling |
| Fast, multiple direct paths | Complex to manage |
| Decentralised |
Seen in: Some businesses, core internet infrastructure, developer environments.
Partial Mesh
Some (but not all) devices have multiple connections, a compromise between full mesh and star.
| Advantages | Disadvantages |
|---|---|
| More resilient than star | Still more cabling than star |
| Cheaper than full mesh | Not fully redundant |
Seen in: Everywhere, most real-world networks are partial meshes.
Topology Comparison
| Topology | Reliability | Cost | Security | Performance |
|---|---|---|---|---|
| Bus | Low | Cheap | Low | Degrades with load |
| Star | Moderate | Moderate | High | Good |
| Full Mesh | Very high | Expensive | Moderate | Very fast |
| Partial Mesh | High | Moderate | Moderate | Good |
Exam Questions
Q: State one disadvantage of a bus topology.
If the backbone cable breaks, the entire network fails as all devices share the same cable.
Q: Why is a star topology more reliable than a bus topology?
Each device has its own connection to the switch. If one connection fails, only that device is affected, not the whole network.
Q: What is the main advantage of a full mesh network?
Multiple paths exist for data. If one connection fails, traffic can be rerouted, maintaining network availability.
Q: Give one disadvantage of a mesh topology.
It requires a large amount of cabling and equipment, making it expensive and complex to install.
Exam Tip
Single points of failure: bus = the backbone cable; star = the central switch. Full mesh eliminates single points of failure; partial mesh reduces them.