Network topologies

## What is a topology? A **topology** is the shape of how devices are connected to each other. ``` Star Bus Ring PC PC PC PC PC PC ── PC \ / │ │ │ │ │ PC ── SW ── PC ═╧════╧════╧═ PC ── PC / \ PC PC ``` | Topology | Good side | Weak side | |---|---|---| | **Star** | If one cable breaks, only one computer is cut off. The most common today | If the central switch breaks, everything goes down | | **Bus** | Little cable | If the main cable breaks, the whole network stops | | **Ring** | Simple | If one link breaks, there's a problem | | **Mesh** | Very reliable | Lots of cable: n×(n−1)/2 for *n* devices | | **Tree** | Good for buildings and organisations | The top-level switch is critical | A **tree** topology joins many **stars** together: central switch → a switch on each floor → the computers in each room. > 🧮 Problems: **Networks → Level 3**