Understand characteristics of network topologies (bus, star, mesh)

The idea

A network topology is the arrangement of nodes and connections. In a bus topology all nodes share one backbone cable; data travels along the backbone and terminators absorb signals at the ends. It needs little cable but a break in the backbone can stop the whole network and performance falls as traffic increases. In a star topology every node connects to a central switch or hub; a failed node or cable affects only that node, but the central device is a single point of failure. Star is common in schools and offices because it is easy to add nodes and troubleshoot. In a mesh topology nodes connect to multiple other nodes; a full mesh gives every node a direct link to every other node, so it is highly resilient but needs many cables and ports. Partial mesh connects some nodes by more than one path. A useful method is to compare cost, fault tolerance and ease of adding nodes.

What earns the marks

• Bus: all nodes share a single backbone cable, with terminators at each end; a break in the backbone can disrupt the whole network.
• Star: each node connects to a central switch or hub; a single node or cable failure affects only that node, but the central device is a single point of failure.
• Mesh: nodes connect to multiple other nodes; a full mesh links every node directly to every other node, giving high resilience but requiring many connections.
• Partial mesh: some nodes have more than one path to other nodes, balancing resilience against cost.
• Comparison factors: cost of cabling and hardware, fault tolerance, ease of adding or removing nodes, and performance under load.

Common mistakes and how to put them right

• Saying a star topology has no single point of failure.

  Put it right: The central switch or hub is a single point of failure.

• Confusing a bus backbone with a star's central device.

  Put it right: In a bus all nodes share one cable, while in a star each node has its own cable to the centre.

• Thinking a mesh always means every node is directly connected to every other node.

  Put it right: That is a full mesh; a partial mesh has some nodes with multiple links only.

• Ignoring cost: mesh gives high resilience but needs more cable and ports than bus or star.

Exam tips

• Compare topologies using the same factors, such as cost, fault tolerance and ease of adding nodes.
• Link each topology to a realistic context: bus for a small, low-traffic network; star for a school or office; mesh where resilience matters.
• State the effect of a single failure in each topology rather than only describing the layout.