Fundamentals of computer networks: star

The idea

In a star topology every device connects by its own cable or link to a central device, usually a switch. Each device therefore has a dedicated point-to-point connection to the centre, and all traffic passes through that central node. This makes faults easy to isolate: if one cable fails, only that device loses connectivity, while the rest of the network keeps working. Adding a device means running one new link to the centre, so expansion is straightforward. The trade-off is dependence on the centre: if the central switch fails, the whole network goes down. It also needs more cabling than a bus, which raises cost. Contrast this with a bus, where all devices share one backbone cable and a break can affect many users. When answering, identify the central device, explain the dedicated links and weigh the reliability and cost consequences.

What earns the marks

• A star topology connects each device to a central device such as a switch or hub by its own dedicated link.
• A single cable or device failure affects only that device, so the rest of the network continues to operate.
• Adding a new device requires only one new connection to the central device, making expansion simple.
• If the central device fails, the entire network becomes unavailable, which is the main weakness.
• Star topologies use more cabling than a shared bus, increasing installation cost.

Common mistakes and how to put them right

• Thinking devices connect directly to each other in a star.

  Put it right by stressing that every link goes to the central switch.

• Claiming a single cable fault brings down the whole star network.

  Put it right by noting only the affected device loses connection.

• Ignoring the central point of failure.

  Put it right by stating that central device failure disables the whole network.

Exam tips

• Name the central device explicitly, for example a switch, rather than saying 'a centre'.
• Give one advantage and one disadvantage with a reason, such as easy fault isolation or dependence on the centre.
• Compare with another topology only when the question asks, and keep the comparison to one clear point.