Which of the following protocols utilizes distance-vector routing?

Distance-vector routing is a type of routing protocol where routers periodically share information about the entire network's reachability and distance from their own routing table. The Routing Information Protocol (RIP) is a classic example of a distance-vector routing protocol, relying on the number of hops to determine the best path to a destination. It uses a metric called hop count and can support a maximum of 15 hops, with 16 being considered an unreachable destination.

In RIP, routers share their routing tables with neighboring routers at regular intervals. This information exchange allows routers to update their knowledge about the network topology, but it doesn't consider other metrics like bandwidth or delay, which are aspects of more advanced routing protocols.

Conversely, protocols like Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS) use link-state routing, which involves a more complex mechanism for exchanging information about the state of links in the network. Border Gateway Protocol (BGP) operates differently as a path vector protocol that uses path information as its routing metric and is designed for use between different autonomous systems.

Therefore, the emphasis on the distance metric and the way RIP operates with periodic updates of routing tables clearly identifies it as a distance-vector routing protocol.