Networks : Hubs and Switches

The most common network topology is the bus (or line) topology. It is cheap and easy to set up a bus network because relatively little cable is required but bus networks are not as reliable as other topologies. If the main cable breaks anywhere along the network the computers connected to it will no longer be able to communicate with each other.

One way to reduce the effect of a cable break is to split the network up into sections using hubs or switches. This diagram shows a bus network that has been split up into three sections :

• The main network cable is known as the backbone. It will use a fast transmission medium such as fibre optic cable.
• Devices called hubs or switches are connected to the backbone.
• Each computer is connected to a hub/switch by its own cable. Through the hub the computers can communicate with other computers on the network.

A sectioned network is more reliable than a standard bus topology. If a cable connecting a computer to a hub breaks then only that one computer will be affected. All of the other computers will continue to be able to use the network (note however that if the main backbone cable fails none of the computers will be able to use the network).

Hubs and switches are also used to connect together the computers at different levels in a hierarchical network.

GCSE ICT Companion 04 - (C) P Meakin 2004