OSPF is a link-state routing protocol。It is designed to be run internal to a single （）system。Each OSPF router maintains an identical （）describing the autonomous system’s topology。From this database，a routing table is calculated by constructing a shortest-path （73）。OSPF recalculates routes quickly in the face of topological changes，utilizing a minimum of routing （） traffic。OSPF provides support for equal-cost multipath。An area routing capability is provided，enabling an additional level of routing protection and a reduction in routing protocol （）。