ABSTRACT
Intermediate System-to-Intermediate System (IS-IS) is a link-state routing protocol and an IGP similar to OSPF, and is used for distributing routing information within an autonomous system. IS-IS also uses the Shortest-Path First (SPF) algorithm (a variant of the Dijkstra algorithm) to calculate loop-free routes to network destination. Compared to RIP, IS-IS was designed to respond quickly to network topology changes just like OSPF (both exhibit the same convergence properties), but IS-IS uses relatively fewer routing protocol messages and generates less protocol traffic when compared to OSPF.
