REASON FOR MULTIPLE TOPOLOGIES
Every topology has disadvantages and advantages, which are described below:
IN A RING:
It is simple to coordinate access to other devices however entire network is disabled if a cable cut happens.
IN A STAR:
On the other hand only once device is affected when a cable cut happens.
IN A BUS:
The network uses fewer wires than a star, however entire network is disabled when a cable cut happens.