Purdue Model

What is the Purdue Model?

The Purdue Model (Purdue Enterprise Reference Architecture - PERA) is a hierarchical reference model developed at Purdue University that describes the functional layers in industrial automation environments. The model defines six levels, from field devices (Level 0) to business planning systems (Level 5).

The Purdue Model levels: Level 0 - physical process (sensors, actuators). Level 1 - controllers (PLCs, RTUs, DCS). Level 2 - supervisory systems (SCADA, HMI, engineering workstations). Level 3 - operations management (MES, data historians, production databases). Level 3.5 - Industrial DMZ. Level 4 - business systems (ERP, CRM, email). Level 5 - corporate network and Internet.

The Purdue Model forms the foundation of the zones and conduits concept in the IEC 62443 standard. Each level should be separated by security controls, and communication between levels should pass through defined conduits with appropriate filtering rules.

Why does it matter?

The Purdue Model gives organisations a common language for describing OT network architecture and planning segmentation. In practice, many industrial installations deviate from the ideal model - devices from different levels communicate directly, bypassing intermediate layers. A Purdue Model compliance audit helps identify such deviations and plan network segmentation in line with best practices and IEC 62443 requirements.

Related topics

• Industrial DMZ
• IEC 62443
• Defence in Depth