OSPF Protocol

OSPF Protocol stands for open shortest path first.

Its a routing protocol for Internet Protocol networks.
If network is based on IP, the OSPF algorithm will calculate the most efficient way for data to be transmitted.
OSPF has largely replaced RIP protocol in most of corporate networks.
It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous system (AS).

Following diagrams will help you understand why OSPF protocol is necessary !!

Basic network topology with data flow.

If we see above network the data/traffic from source to destination is going via router A-H-D.
Let assume this path is the primary and is assigned by user after calculating the shortest path manually.Whenever, there will be any issue in the network the user needs to manually check shortest path and reassign.
Which is definitely cumbersome and time consuming if user have a huge network with many routers.

Fibre cut between router A and H