Which of the following statements is/are INCORRECT about the OSPF (Open Shortest Path First) routing protocol used in the Internet?

OSPF (Open Shortest Path First) is an open-standard link-state routing protocol:

• Statement (A) is INCORRECT: OSPF is a link-state routing protocol that utilizes Dijkstra's Shortest Path First (SPF) algorithm to compute the shortest path tree from the source router to all destination networks. The Bellman-Ford algorithm is used by Distance-Vector routing protocols such as RIP (Routing Information Protocol).

• Statement (B) is CORRECT: Each router running OSPF builds a complete topological database of the network and runs Dijkstra's algorithm to compute the least-cost paths.

• Statement (C) is INCORRECT: OSPF is an intra-domain (Interior Gateway Protocol - IGP) routing protocol used within an Autonomous System (AS). Inter-domain routing is typically handled by protocols such as BGP (Border Gateway Protocol).

• Statement (D) is CORRECT: OSPF supports hierarchical routing by dividing an Autonomous System into multiple areas, with a central backbone area (Area 0) interconnecting non-backbone areas.

Therefore, the incorrect statements are A and C.