Chapter 2 Advanced Routing for FortiOS 5.0 : Intermediate System to Intermediate System Protocol (IS-IS) : IS-IS background and concepts : Parts and terminology of IS-IS
  
Parts and terminology of IS-IS
Before you can understand how IS-IS functions, you need to understand some of the main concepts and parts of IS-IS.
This section includes:
DIS election and pseudonode LSP
Packet types
Default routing
Timer options
Authentication
Integrated IS-IS