IS-IS - Wikipedia
https://en.wikipedia.org/wiki/IS-IS
Intermediate System to Intermediate System (IS-IS, also written ISIS) is a routing protocol designed to move information efficiently within a computer network...
IS-IS Overview - TechLibrary - Juniper Networks
https://www.juniper.net/documentation/en_US/junos/topics/concept/is-is-routing-overview.html
IS-IS Terminology, ISO Network Addresses, IS-IS Packets, Persistent Route Reachability, IS-IS Support for Multipoint Network Clouds, Installing a Default Route to the Nearest Routing Device That Operates...
course-page-is-is | NetworkLessons.com
https://networklessons.com/is-is
Like any other routing protocol, IS-IS supports authentication. You can choose between plain text or HMAC-MD5 authentication, and there are some different options that define which packets will be...