RIB (Routing Information Base) update is the last post of OSPF fast convergence series whereas earlier posts have already covered OSPF Event Detection, OSPF Event Propagation and OSPF Event Processing.

Whenever there is change of interface state arises, OSPF detect that change and according to that Dijkstra runs the algorithm and update the RIB table according to that. This process is time consuming and requires lot of CPU and memory cycles.