Open Shortest Path First (OSPF) is a routing protocol that has a significant place in internet infrastructure. It is one of the Interior Gateway Protocol (IGP) which helps to find the best routing path between the source and the destination router using its own shortest path first (SPF) algorithm. It is a Link State Routing Protocol that is used to distribute routing information about data packets within a large Autonomous System. Being able to find the shortest path easily and quickly helps in reducing unnecessary network load and the ability to find another path in case of error at the optimal one helps in increasing the stability of the network.
An autonomous system can be divided into areas, these help in reducing the link state advertisements and other overhead traffic that will be otherwise sent to the network.
When it is configured, it listens to its neighbors in the networks and it gathers all the link state data available. This data is then used to make a topology map that contains all available paths in the network. This database is saved and called Link State Database.
Once the Link State Database is made it is used to calculate the shortest path to subnets/ networks using an algorithm known as Shortest Path First which was developed by Edsger W Dijkstra.