What is a distance vector routing protocol?

Distance vector is a type of routing protocol which use Bellman–Ford algorithm, ford algorism to calculate the best path example of Distance vector routing protocol is RIP in distance vector protocol every router send periodic update to its neighbor about the network path it discover unlike link state Protocol which send update only when topology Changed  and it is now not use quit often for large network since its low convergence time, todays popular link state OSPF, EIGRP

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 

• DISTANCE VECTORDistance:    Distance is the cost of reaching a destination, usually based on the number of hosts the path passes through, or the total of all the administrative metrics assigned to the links in the path.Vector:    From the standpoint of routing protocols, the vector is the interface traffic will be forwarded out in order to reach an given destination network along a route or path selected by the routing protocol as the best path to the destination network. Distance vector protocols use a distance calculation plus an outgoing network interface (a vector) to choose the best path to a destination network. The network protocol (IPX, SPX, IP, Appletalk, DECnet etc.) will forward data using the best paths selected.Common distance vector routing protocols include:    Appletalk RTMP    IPX RIP    IP RIP    IGRP