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.