In routing, the route can be determined dynamically or statically. The main advantage of dynamic routing over static routing is that the route selection is dynamic, i.e. it takes place during ongoing network operation, and network expansions, load changes and overloads are taken into account by the routing algorithm. This type of route adaptation is also called adaptive routing, since the path selection is "adapted" to the current network situation.
In dynamic routing, the optimal path selection is weighted by metrics. After parameter setting at the beginning of the procedure, the optimal route is determined by the routing protocol alone and is thus transparent to the user. The metrics for such dynamic routing protocols realize central functions of the network and, compared to static routing, take into account the shortest, cheapest, fastest or safest path, as well as congestion, queues, and line and node failures with the possibility to build alternative routes.
The high flexibility of dynamic methods is achieved by the fact that the routers involved constantly exchange control information about the currently available configuration and topology. This causes additional overhead, which is directly reflected in the network load.
There are several routing protocols that support adaptive routing through different algorithms. Such as the Routing Information Protocol( RIP), Open Shortest Path First( OSPF), Intermediate System to Intermediate System Protocol( IS-IS), Interior Gateway Routing Protocol( IGRP) and others. The RIP protocol, which uses distance vector algorithm, creates routing tables that change during operation. In contrast, Open Shortest Path First (OSPF) is characterized by the fact that it captures the availability of the connection paths, and the IS-IS protocol, unlike the mentioned ones, works with the link-state algorithm.