Routing Protocol Technologies

Routing protocols are based either on a distance vector, link state, or path vector technology.

Distance Vector: Distance vector routing protocols propagate routing information in the form of a network ID and its "distance" (hop count). Routers use distance vector-based routing protocols to periodically advertise the routes in their routing tables. Routing information exchanged between typical distance vector-based routers is unsynchronized and unacknowledged. The advantages of distance vector-based routing protocols include simplicity and ease of configuration. The disadvantages of distance vector-based routing protocols include relatively high network traffic, a long convergence time, and inability to scale to a large or very large network.

Link State : Routers using link state-based routing protocols exchange link state advertisements (LSAs) throughout the network to update routing tables. LSAs consist of a router's attached network prefixes and their assigned costs and are advertised upon startup and when changes in the network topology are detected. Link state updates are sent using unicast or multicast traffic rather than broadcasting. Link state routers build a database of link state advertisements and use the database to calculate the optimal routes to add to the routing table. Routing information exchanged between link state-based routers is synchronized and acknowledged.The advantages of link state-based routing protocols are low network overhead, low convergence time, and the ability to scale to large and very large networks. The disadvantages of link state-based routing protocols are that they can be more complex and difficult to configure.

Path Vector : Routers use path vector-based routing protocols to exchange sequences of hop numbers, for example autonomous system numbers, indicating the path for a route. An autonomous system is a portion of the network under the same administrative authority. Autonomous systems are assigned a unique, autonomous system identifier. Routing information exchanged between path vector-based routers is synchronized and acknowledged. The advantages of path vector-based routing protocols are low network overhead, low convergence time, and the ability to scale to very large networks containing multiple autonomous systems. The disadvantages of path vector-based routing protocols are that they can be complex and difficult to configure.