The Integrated IS-IS is a routing protocol used to integrate IS-IS ( Intermediate System to Intermediate System) and TCP/IP via Open Shortest Path First
(OSPF). The Integrated IS-IS protocol was specified by Digital Equipment in 1990 under RFC 1195. In order to perform IP communications, some information was added to the IS-IS frame. However, the integration achieved comes at the expense of option capabilities in OSPF. OSPF increases the performance and functionality of TCP/IP networks quite considerably compared to Routing Information Protocol
(RIP), but it does not yet provide OSI compatibility and functionality. The goal of Integrated IS-IS is obviously to migrate TCP/IP to Open Systems Interconnection (OSI).