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, a group of physically connected computers or similar devices. It accomplishes this by determining the best route for data through a packet switching network.

The IS-IS protocol is defined in ISO/IEC 10589:2002^[2]^[3] as an international standard within the Open Systems Interconnection (OSI) reference design. The Internet Engineering Task Force (IETF) republished IS-IS in RFC 1142, but that RFC was later marked as historic by RFC 7142 because it republished a draft rather than a final version of the (International Organization for Standardization) ISO standard, causing confusion.

In 2005, IS-IS was called "the de facto standard for large service provider network backbones."^[4]

^ "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 10 March 2023.
^ "ISO/IEC 10589:2002 – Information technology – Telecommunications and information exchange between systems – Intermediate System to Intermediate System intra-domain routeing information exchange protocol for use in conjunction with the protocol for providing the connectionless-mode network service (ISO 8473)". ISO website. International Organization for Standardization (ISO). November 2002. Retrieved May 24, 2017.
^ "Free-of-charge PDF copy of ISO/IEC 10589:2002". ISO website. International Organization for Standardization. Retrieved May 24, 2017.
^ Gredler, Hannes; Goraiski, Walter (2005). The complete IS-IS routing protocol. Springer. p. 1. ISBN 1-85233-822-9.

[1] "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 10 March 2023.

[iso-store-2] "ISO/IEC 10589:2002 – Information technology – Telecommunications and information exchange between systems – Intermediate System to Intermediate System intra-domain routeing information exchange protocol for use in conjunction with the protocol for providing the connectionless-mode network service (ISO 8473)". ISO website. International Organization for Standardization (ISO). November 2002. Retrieved May 24, 2017.

[iso-free-pdf-3] "Free-of-charge PDF copy of ISO/IEC 10589:2002". ISO website. International Organization for Standardization. Retrieved May 24, 2017.

[4] Gredler, Hannes; Goraiski, Walter (2005). The complete IS-IS routing protocol. Springer. p. 1. ISBN 1-85233-822-9.

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