Each link state advertisement describes a piece of the OSPF routing domain. Every router originates a router links advertisement. In addition, whenever the router is elected Designated Router, it originates a network links advertisement. Other types of link state advertisements may also be originated (see Section 12.4). All link state advertisements are then flooded throughout the OSPF routing domain. The flooding algorithm is reliable, ensuring that all routers have the same collection of link state advertisements. (See Section 13 for more information concerning the flooding algorithm). This collection of advertisements is called the link state (or topological) database.
From the link state database, each router constructs a shortest path tree with itself as root. This yields a routing table (see Section 11). For the details of the routing table build process, see Section 16.