IS-IS

Computer network routing protocol Intermediate System to Intermediate System (IS-IS, also written ISIS) is a link-state interior gateway protocol (IGP), typically deployed within a single autonomous system, and is used in large enterprise and service-provider networks to exchange routing information. The IS-IS protocol is defined in ISO/IEC 10589:2002 as an international standard in the Open Systems Interconnection (OSI) model. IS-IS operates by flooding link-state information through a network of routers. Each IS-IS router builds its own link-state database (LSDB) by collecting the flooded link-state information from other routers. Like Open Shortest Path First (OSPF), IS-IS uses Dijkstra's algorithm for computing the shortest paths through the network. Packets (datagrams) are then forwarded along the computed shortest paths to their destinations. History IS-IS was developed by Digital Equipment Corporation as part of DECnet Phase V. The Internet Engineering Task Force (IETF) published an IS-IS specification in 1990, but that RFC was retracted and marked "historic" because it republished a draft rather than a final version of the International Organization for Standardization (ISO