What type of routing protocol uses a directory to share information about distance to destinations?

Link-state protocols use a directory, commonly referred to as a topology database, to share information about the distance to various destinations in the network. These protocols operate by having each router generate and distribute link-state advertisements (LSAs), which provide detailed information about the router's direct neighbors and the status of the links to those neighbors.

This detailed information allows each router to construct a complete view of the network topology, enabling them to calculate the shortest paths to all other nodes using algorithms such as Dijkstra's algorithm. The reliance on a central database of network state information differentiates link-state protocols from others, allowing for faster convergence and more efficient routing decisions.

In contrast, distance-vector protocols share routing information that encompasses only the distance to destinations and the direction (vector) to reach them, but they do not maintain a comprehensive directory of the entire network. Path-vector protocols are primarily used in exterior gateway protocols and focus on the path taken to reach a destination rather than distances. Static routing protocols do not involve dynamic sharing of routing information; they require manual configuration of routes by a network administrator.

Thus, link-state protocols are designed specifically to maintain and use a directory for comprehensive routing information, which aids in creating a robust routing environment.