IS-IS
Intermediate System-to-Intermediate System (IS-IS) is a link state routing
protocol that is part of the OSI family of protocols. Like OSPF, it uses
Dijkstra’s SPF algorithm to choose routes. IS-IS is a classless interior
gateway protocol that uses router resources efficiently and scales to large
networks, such as large Internet service providers (ISP).
Table 4-1 lists some IS-IS terms, acronyms, and their meanings.