what is ospf

Open Shortest Path First (OSPF) is a routing protocol used to distribute IP routing information throughout a single Autonomous System (AS) in an IP network. It is an open standard and is designated by the Internet Engineering Task Force (IETF) as one of several Interior Gateway Protocols (IGPs) within the family of TCP/IP protocols. OSPF uses a link-state routing (LSR) algorithm, which is a departure from the Bellman-Ford vector-based algorithms used in traditional Internet routing protocols such as RIP. OSPF has many features that allow the imposition of policies about the propagation of routes that it may be appropriate to keep local, for load sharing, and for selective route importing. OSPF is widely deployed and can converge a network in a few seconds while guaranteeing loop-free paths. OSPF runs over IPv4 and IPv6, but does not use a transport protocol such as UDP or TCP. It encapsulates its data directly in IP packets with protocol number 89. OSPF also uses multicast addressing for distributing route information within a broadcast domain.