Purdue model (Purdue Enterprise Reference Architecture)
A layered reference model that sorts industrial systems into levels, from the physical process and field devices at the bottom to business systems at the top, widely used to plan OT network segmentation.
The network analogy
Core, distribution, and access layers applied to plant functions instead of switches, with the rule that each level talks mainly to its neighbors.
Why it matters for wireless
NIST recommends permitting connections only between adjacent levels, so a single wireless network shared by control devices and business clients cuts across the model it is supposed to follow.
The Purdue model and the plant floor zones
Cell/area zones, where devices exchange control traffic, span Levels 0 to 2.
ISA-95 builds on the Purdue reference model with five levels, from the physical process at Level 0 to business planning at Level 4; the industrial DMZ between plant and enterprise is commonly called Level 3.5. NIST recommends firewall rules that keep Level 4 from reaching Levels 2, 1, and 0 directly. "Cell/area zone" comes from a jointly published vendor architecture, not a standard.
Sources: NIST SP 800-82r3, ISA-95, and a jointly published plantwide Ethernet design guide.
NIST names the Purdue model, ISA-95 levels, and the three-tier IIoT architecture1 as recognized ways to organize OT segmentation, with firewall rules that prevent Level 4 devices from directly communicating with Level 2, 1, or 0 devices. The model comes from the Purdue Enterprise Reference Architecture, first published by ISA in 1992, and ISA-95 builds on it with five levels from the physical process at Level 0 to business planning at Level 42.
The industrial DMZ between the plant and the enterprise is often called Level 3.53.
About this page
Built from 3 sources: 2 standards bodies and labs and 1 vendor document. Researched and drafted with AI assistance, then reviewed and approved by Ben Rutter on . How pages are made
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Cite this page
Plain
Ben Rutter. "Purdue model (Purdue Enterprise Reference Architecture)." OT Wireless, published October 5, 2026. https://otwireless.com/glossary/purdue-model/
APA 7
Rutter, B. (2026, October 5). Purdue model (Purdue Enterprise Reference Architecture). OT Wireless. https://otwireless.com/glossary/purdue-model/
BibTeX
@misc{rutter2026purduemodel,
author = {Rutter, Ben},
title = {{Purdue model (Purdue Enterprise Reference Architecture)}},
year = {2026},
howpublished = {\url{https://otwireless.com/glossary/purdue-model/}},
organization = {OT Wireless},
}