The designated router is responsible, among other things, for generating LSAs for the entire multiaccess network. Designated routers allow a reduction in network traffic and in the size of the topological database. When the link state databases of two neighboring routers are synchronized, the routers are said to be adjacent . On multiaccess networks, the designated router determines which routers should become adjacent. Topological databases are synchronized between pairs of adjacent routers.
Adjacencies control the distribution of routing protocol packets.
These packets are sent and received only on adjacencies. LSAs are also sent when a router's state changes. LSAs include information on a router's adjacencies. By comparing established adjacencies to link states, failed routers can be quickly detected and the network's topology altered appropriately. From the topological database generated from LSAs, each router calculates a shortest-path tree, with itself as root.