Editing IS-IS (section)

{{Short description|Computer network routing protocol}}
{{About|a computer network protocol|topics with similar names|Isis (disambiguation)}}
{{OSI model}}
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{{Cleanup rewrite|it is [[WP:NOTHOW|written like a textbook]], with [[MOS:EDITORIAL|editorializing]] and [[WP:COPYEDIT|grammatical errors]]|date=May 2025}}
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'''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 [[routing|route]] for data through a packet switching network.

The IS-IS protocol is defined in ISO/IEC 10589:2002<ref name="iso-store">{{cite web|title=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)|url=https://www.iso.org/standard/30932.html|website=ISO website|publisher=[[International Organization for Standardization]] (ISO)|access-date=May 24, 2017|date=November 2002}}</ref><ref name="iso-free-pdf">{{cite web|title=Free-of-charge PDF copy of ISO/IEC 10589:2002|url=http://standards.iso.org/ittf/PubliclyAvailableStandards/c030932_ISO_IEC_10589_2002(E).zip|website=ISO website|publisher=[[International Organization for Standardization]]|access-date=May 24, 2017}}</ref> as an international standard within the Open Systems Interconnection (OSI) reference design. 

In 2005, IS-IS was called "the [[de facto standard|''de facto'' standard]] for large service provider [[Backbone network|network backbones]]".<ref>{{cite book|last=Gredler|first=Hannes|title=The complete IS-IS routing protocol|year=2005|publisher=Springer|isbn=1-85233-822-9|pages=1|author2=Goraiski, Walter}}</ref>