What is a Topology?
You have six computers to connect in a lab. You could run one long cable past all of them. You could give each one its own cable to a box in the middle. Or something in between. Each choice is a different shape of network.
1The definition
Below are the same six computers wired in five different shapes. Switch between them and watch the cables change.
Pick a shape. Then break something and send a message.
2Why the shape matters
The shape decides the answers to three practical questions:
More cable costs more money and more work to lay.
Does one computer lose the network, or does everyone?
Can you add a computer without disturbing the others?
Try it in the lab: cut PC C’s cable in each shape, then make the central device fail. The same kind of fault does very different damage.
3The five shapes
Your syllabus names three of these — bus, star and tree. Ring and mesh appear in many textbooks and are worth knowing too, so they have lessons of their own.
All computers share one main cable, called the backbone.
Each computer has its own cable to a central hub or switch.
Several stars joined to one backbone — bus and star together.
Each computer is cabled to the next, in a closed loop.
Every computer is cabled directly to every other.
4Topology is not the same as network type
The last chapter sorted networks by how far they reach — PAN, LAN, MAN, WAN. Topology is about shape. The two answer different questions, so a network has both: your school lab is a LAN (type) wired as a star (topology).
5Check yourself
The topology of a network describes…
A school lab has each computer cabled to a central switch. Which is correct?