RSTP was introduced to overcome the limitations of the spanning tree protocol (STP).
Advantage of STP:
Though STP ensures a loop-free network.
Problem with STP:
With increased topology changes, STP slows down the network topology convergence speed, leading to service deterioration causing regular interruption.
RSTP employs a proposal and agreement process which allows for immediate negotiation of links to take place, effectively removing the time taken for convergence based timers to expire before spanning tree convergence can occur. The proposal and agreement process tends to follow a cascading effect from the point of the root bridge through the switching network, as each downstream switch begins to learn of the true root bridge and the path via which the root bridge can be reached.