Link-state routing protocols determine least-cost routes by modeling the entire network. This is accomplished through the exchange of link state advertisements throughout the network, which each router uses to update its link-state database. Once these databases are fully populated, link-state routers implement an algorithm such as Dijkstra's Shortest Path First to determine a unique least-cost pathway to each potential destination.
Link-state routing protocols contrast with distance-vector protocols. Distance-vector protocols do not model the entire network. For this reason, link-state protocols are generally considered more stable and reliable, whereas distance-vector protocols may be a bit simpler to implement. Link-state protocols scale much better, however, and are suitable for use by large autonomous systems (AS).
Open Shortest Path First (OSPF) is one example of link-state routing protocol.