Every routing protocol uses a routing algorithm to facilitate the decision-making process for routers. A routing algorithm is a formula used to calculate the best path between two networks. The algorithm uses information gathered by the routing protocols, known as metrics, to compute the best path.
The two major types of routing algorithms are distance vector and link-state. Distance vector algorithms generally use one metric to calculate the lowest cost from source to destination. Link-state protocols use multiple metrics to calculate the shortest distance from a source to a destination one hop at a time.