OSPF - Open Shortest Path First

Open Shortest Path First is the most widely used Interior gateway protocol (IGP) that uses the link state routing algorithm to construct the network graph. The current version of the OSPF protocol for IPv4 is OSPF version 2. The changes for IPv6 is specified in OSPF version 3.

OSPF is an open-source protocol and works with a wide variety of routing devices from any manufacturer. It is his biggest advantage over EIGRP that works only with the Cisco devices.

How does OSPF works?
OSPF protocol is quite suitable to distribute routing information to a group routers in a specific network known as Autonomous system (AS). In the OSPF protocol, routers exchange topology information with their neighboring routers within the AS. In this way, each and every system in the AS get to know the complete picture of the topology. It helps in calculating the shortest path from one end to another, using the variant of the Dijkstra algorithm.

This arrangement of the OSPF protocol is only suitable for a smaller network structure. The architecture would be a problem once more routers are added to the routing domain. Increasing the number of routers will increase the topology updates, and the time it takes to calculate the end-to-end routes. Due to this problem, OSPF is only suitable for routing traffic within a single AS.