OSPF is a standardized protocol for routing IPv4, developed in 1988 by the Internet Engineering Task Force to replace RIP in larger, more diverse media networks. In 1998, minor changes in OSPF version 2 (OSPFv2) addressed some of OSPF version 1’s problems while maintaining full backward compatibility. OSPF was developed for use in large scalable networks in which RIP’s inherent limitations failed to satisfy requirements. OSPF is superior to RIP in all aspects, including the following:

■ It converges much faster.

■ It supports VLSM, manual summarization, and hierarchical structures.

■ It has improved metric calculation for best path selection.

■ It does not have hop-count limitations.

OSPF Characteristics

OSPF is a link-state protocol that has the following characteristics for deployment in enterprise networks:

■ Fast convergence: OSPF achieves fast convergence times using triggered link-state updates that include one or more link-state advertisements (LSA). LSAs describe the state of links on specific routers and are propagated unchanged within an area. Therefore, all routers in the same area have identical topology tables; each router has a complete view of all links and devices in the area. Depending on their type, LSAs are usually changed by ABRs when they cross into another area.