Network topologies

What is a network topology?

• Physical arrangement of the devices in a communications network.

• Most commonly used are bus and star.• Usually a combination of these two, referred

to as hybrid or tree networks.

Bus topology

• Many devices connect to a single cable ("backbone“).

• If the backbone is broken, the entire segment fails.

• Relatively easy to install and don't require much cabling compared to the alternatives.

Ring topology

• Every device has two neighbours for communication purposes.

• Messages travel through a ring in the same direction.

• A failure in any cable or device breaks the loop and will take down the entire segment.

• If any device is added to or removed from the ring, the ring is broken and the segment fails until it is reforged“.

• Considerably more expensive than other topologies.

Star topology

• Has a central connection point - like a hub or switch. • Involves more cable• If a cable fails, only one node will be brought down.• The central hub is usually a fast, self contained computer

and is responsible for routing all traffic to other nodes. • The main advantage of a star network is that one

malfunctioning node does not affect the rest of the network.

• Can be prone to bottleneck and failure problems at the central site.

Hybrid/tree topology

• Also known as the 'Hierarchical topology‘.• A combination of bus and star topologies. Very

common in larger networks. • Typical scenario is: a file server is connected to

a backbone cable that runs through the building, from which switches are connected, branching out to workstations.

Activities

• Make a list of advantages/disadvantages for the topologies.

• What topologies to you feel are outdated?• What type of topology does the school use?

Why do you think they have chosen this one?• What topology would you suggest for a small

business? Home network? Large business? Why?