Data moves in one direction around the ring. Normally, ring networks use tokens to designate which node has the right to communicate. Each node replicates the signal, so very little degradation occurs. No collisions occur because of the token scheme. Fault tolerance keeps your network running even when one segment goes down.
Ring topology is expensive to buy and maintain.
A break in the line can bring down the network, but most have more than one line. Harder to support because it is not popular.