Link State $-$

Open Shortest Path First $($OSPF$)-$ OSPF is a link state routing protocol that uses the Shortest Path First $($SPF$)$ algorithm to determine the best path to a destination network. It exchanges link state information with neighboring routers and builds a complete topology map of the network.

Intermediate System to Intermediate System $($IS$-$IS$)-$ IS$-$IS is another link state routing protocol commonly used in large$-$scale networks. It operates similarly to OSPF, exchanging link state information with neighboring routers to build a complete network topology. IS$-$IS is often used in service provider networks.