Open Shortest Path First

A gateway-routing protocol created for IP networks that implements the “shortest path first” (or link-state) algorithm. Routers use the algorithms to forward routing information to all other OSPF routers on the Internet by calculating the shortest path to each router, based on a connection graph of the network as it is “seen” by each router.

Each router sends not only the portion of the routing table describing the state of its own links but also the complete routing structure (known as the topography). The positive aspect of “shortest path first” algorithms is that they produce smaller, more frequent updates, thus preventing problems such as routing loops and count-to-infinity (which occurs when routers continue to increment the distance counter to a destination net).

OSPF results in a stable network. OSPF’s major disadvantage is its large requirement of CPU power and memory. The advantages far outweigh the costs, however.

See Also: Algorithm; Internet; Protocol; Routers.