OSPF does not require each router to send its entire routing table to its neighbors. Instead, each OSPF router floods only link-state change information in the form of LSAs throughout the area or AS. LSAs in OSPF are one of the following five types:
A router links advertisement is flooded only within the area and contains information about neighbor routers and the LANs to which the router attaches. A backbone router can flood router link advertisements within the backbone area.
A DR on a LAN generates network links advertisement to list all routers on that LAN, and floods network links advertisements only within the area. A backbone DR can flood network links advertisements within the backbone area.
An ABR floods a network summary link advertisement into an area and describes networks that are reachable outside the area. An ABR attached to two areas generates a different network summary link advertisement for each area. ABRs also generate area summary link advertisements that contain information about destinations within an area that are flooded to the backbone area.
An ASBR summary link advertisement describes the cost of the path to an ASBR from the router that generates the advertisement.
An ASBR sends an ASE link advertisement to describe the cost of the path to a destination outside the AS from the ASBR that generates the advertisement. This information is flooded to all routers in the AS.