Ebook: OSPF Design Guide : Cisco Systems Network Supported Accounts, Rev: 1.1 April, 1996

OSPF (Open Shortest Path First) protocol was developed due to a need in the internet community to introduce a high functionality non-proprietary Internal Gateway Protocol (IGP) for the TCP/IP protocol family. The dis- cussion of creating a common interoperable IGP for the Internet started in 1988 and did not get formalized until 1991. At that time the OSPF Working Group requested that OSPF be considered for advancement to Draft Internet Standard.
The OSPF protocol is based on link-state technology which is a departure from the Bellman-Ford vector based algorithms used in traditional Inter- net routing protocols such as RIP. OSPF has introduced new concepts such as authentication of routing updates, Variable Length Subnet Masks (VLSM), route summarization, etc.
In the following chapters we will discuss the OSPF terminology, algorithm and the pros and cons of the protocol in designing the large and compli- cated networks of today.