Which routing protocol is characterized by link-state information exchange?

The routing protocol that is characterized by link-state information exchange is Open Shortest Path First (OSPF). OSPF operates by having routers share information about their local state with other routers in the same area of the network. This allows each router to build a complete and updated topology of the network, which is then used to calculate the shortest path to each destination using Dijkstra's algorithm.

In contrast, other protocols mentioned have different fundamental mechanisms for routing. For example, Routing Information Protocol (RIP) uses a distance-vector approach, where routers share information about the distance to reach various networks based on hop count, rather than the state of links. Enhanced Interior Gateway Routing Protocol (EIGRP) combines principles from both distance-vector and link-state protocols but does not purely function as a link-state protocol. Border Gateway Protocol (BGP), on the other hand, is primarily used for routing between different autonomous systems and utilizes path vector mechanics, not a link-state exchange.

Due to these factors, OSPF is the protocol that uniquely employs link-state information exchange, making it efficient for converging rapidly in dynamic network environments.