Which protocol uses a link-state routing algorithm?

Open Shortest Path First (OSPF) is the correct answer because it is specifically designed as a link-state routing protocol. In a link-state routing algorithm, routers maintain a complete map of the network topology by sharing information about their connectivity and link costs with all other routers in the network. Each router builds a complete database of the network's topology and then uses an algorithm, typically Dijkstra's algorithm, to compute the shortest path to each network destination based on that topology.

This method allows OSPF to respond quickly to topology changes and scale effectively in larger networks compared to distance-vector protocols. With OSPF, routers maintain more precise and granular knowledge of the network, resulting in more efficient route calculations and better overall network performance.

In contrast, the other protocols mentioned have different operational methodologies. The Routing Information Protocol (RIP) is a distance-vector protocol that makes routing decisions based on the number of hops rather than the topology of the network. Border Gateway Protocol (BGP) is classified as a path-vector protocol primarily used for routing between different autonomous systems and does not utilize a link-state approach. Enhanced Interior Gateway Routing Protocol (EIGRP), while incorporating features from both distance-vector and link-state protocols, is not fundamentally a link-state protocol