OSPF

A link-state interior routing protocol.

Open Shortest Path First is a link-state interior gateway protocol that routers use to share topology information and compute efficient paths within an autonomous system. Each router builds a map of the network and selects routes based on a cost metric, converging quickly after changes. From a security standpoint, OSPF should use authentication so that malicious or misconfigured devices cannot inject false routes that cause traffic interception or denial of service. It contrasts with exterior protocols like BGP, which exchange routes between separate autonomous systems.