Which algorithm does OSPF use to construct a loop-free topology?

OSPF (Open Shortest Path First) uses the Dijkstra Shortest Path First (SPF) algorithm to construct a loop-free topology within an IP network. The Dijkstra SPF algorithm is designed to compute the shortest path from the OSPF router to all reachable nodes in the network, ensuring that the paths used are optimal and free from loops.

When OSPF routers exchange routing information, they maintain a topology map of the network called the Link-State Database (LSDB). Using the Dijkstra SPF algorithm, each OSPF router calculates the shortest path to each destination based on the metric values (which are typically based on bandwidth). The result is a Shortest Path Tree (SPT) where the loop-free nature is guaranteed due to the algorithm's design, which systematically evaluates each path and eliminates those that would create a loop.

In contrast, while other algorithms like the Bellman-Ford algorithm are used in distance-vector protocols, they operate on different principles and can potentially allow for routing loops. The Ford-Fulkerson algorithm is associated with network flow problems and is not relevant to routing protocols, and the BFS algorithm is primarily used for searching tree or graph structures rather than finding optimal paths in a network. Thus, the Dijkstra SPF