Open Shortest Path First (OSPF) is the most prevalent link-state routing protocol. OSPF is the most common protocol that routers use to determine the optimal path to forward traffic. The OSPF Working Group of the Internet Engineering Task Force (IETF) designed it. OSPF development began in 1987, and there are currently two active versions:

• OSPFv2: OSPF for IPv4 networks (RFC 1247 and RFC 2328)
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• OSPFv3: OSPFv3 is the IPv6 version of OSPF (RFC 2740)

OSPFv3 now supports both IPv4 and IPv6 thanks to the Address Families functionality.

OSPF implements the link state routing algorithm and is utilized in medium- to large-sized networks. OSPF is an intradomain routing protocol that only operates within a specific routing domain. OSPF is also a hierarchical routing protocol that may be used in a single autonomous system. OSPF emerged from the intermediate-system-to-system (IS-IS) routing protocol of the Open Systems Interconnection (OSI) reference model. OSPF enables multipath routing and uses one or more routing metrics, including dependability, bandwidth, latency, load, and maximum transmission unit (MTU). If OSPF utilizes many metrics, it also allows type-of-service (TOS) requests for traffic differentiation.

OSPF, is a link-state, interior gateway, and classless protocol that uses the shortest path first (SPF) algorithm to ensure efficient data transmission. Internally, this type maintains numerous databases containing topology tables and network-wide information. Typically, the data is derived from link state advertising transmitted by individual routers. The advertising, which resembles reports, provides thorough details of the path's length and the resources that may be necessary.

OSPF utilizes the Dijkstra algorithm to recalculate paths when topology changes occur. It also employs authentication procedures to maintain the security of its data throughout network modifications and intrusions. Due to its scalability, OSPF may be advantageous for both small and large network enterprises.