Appendix C. Integrated IS-IS Basics of Operation

Intermediate System-to-Intermediate System (IS-IS) was standardized by the International Telecommunication Union (ITU) in the International Organization for Standardization (ISO) standard 10589 in 1990. IS-IS was originally designed for use with End System-to-Intermediate System (ES-IS) to provide routing information for Connectionless Network Service (CLNS) and other routed protocols that the ITU standardized.

The Internet Engineering Task Force (IETF) has, over the years, added extensions to IS-IS to support IP routing, Multiprotocol Label Switching (MPLS) traffic engineering (TE), and other capabilities, through a series of RFCs, including these:

RFC 1195—“Use of Open System Interconnection ...

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