This document is a specification of the Open Shortest Path First
(OSPF) TCP/IP internet routing protocol. OSPF is classified as an
Interior Gateway Protocol (IGP). This means that it distributes
routing information between routers belonging to a single Autonomous
System. The OSPF protocol is based on link-state or SPF technology.
This is a departure from the Bellman-Ford base used by traditional
TCP/IP internet routing protocols.
The OSPF protocol was developed by the OSPF working group of the
Internet Engineering Task Force. It has been designed expressly for
the TCP/IP internet environment, including explicit support for IP
subnetting, TOS-based routing and the tagging of externally-derived
routing information. OSPF also provides for the authentication of
routing updates, and utilizes IP multicast when sending/receiving
the updates. In addition, much work has been done to produce a
protocol that responds quickly to topology changes, yet involves
small amounts of routing protocol traffic.
The author would like to thank Fred Baker, Jeffrey Burgan, Rob
Coltun, Dino Farinacci, Vince Fuller, Phanindra Jujjavarapu, Milo
Medin, Kannan Varadhan and the rest of the OSPF working group for
the ideas and support they have given to this project.