The Purdue Model, also known as the Purdue Enterprise Reference Architecture (PERA), is a framework used primarily in industrial control systems (ICS) to organize and segment network layers. It helps in structuring and securing operational technology (OT) networks by defining different layers of control and information flow.
Comprehensive Structure of the Purdue Model
The Purdue Model is typically represented as a hierarchical structure with six distinct levels, each serving specific functions in an industrial control system:
Level 0: Physical Process
- Purpose: This level includes the actual physical processes and machinery being controlled.
- Components:
- Sensors (e.g., temperature, pressure, flow sensors)
- Actuators (e.g., motors, valves)
Level 1: Basic Control
- Purpose: Involves real-time control systems directly interfacing with the physical processes.
- Components:
- Programmable Logic Controllers (PLCs)
- Distributed Control Systems (DCS)
- Real-time data collection and basic control algorithms
Level 2: Process Control
- Purpose: Supervisory control that manages and monitors the processes at Level 1.
- Components:
- Human-Machine Interfaces (HMIs)
- Supervisory Control and Data Acquisition (SCADA) systems
- Process historians for data logging
Level 3: Manufacturing Operations Management
- Purpose: Focuses on managing the operations of the manufacturing process.
- Components:
- Manufacturing Execution Systems (MES)
- Workflow and batch management
- Production scheduling and quality control systems
Level 4: Business Planning and Logistics
- Purpose: Manages the overall business operations and integrates with manufacturing processes.
- Components:
- Enterprise Resource Planning (ERP) systems
- Supply chain management
- Customer relationship management (CRM)
Level 5: Enterprise Network
- Purpose: The highest level where enterprise-wide systems and external communications reside.
- Components:
- Corporate IT infrastructure
- Cloud services
- External business systems and services
Security and Segmentation
- Zones and Conduits: The Purdue Model also emphasizes segmenting the network into zones with defined conduits (communication paths) to ensure security. For example, separating IT (Levels 4-5) and OT (Levels 0-3) networks helps protect critical industrial processes from cyber threats.
Benefits of the Purdue Model
- Organizational Clarity: Clear demarcation of responsibilities and functions across different levels.
- Enhanced Security: By segmenting and isolating critical systems, the model reduces the risk of widespread disruptions from cyberattacks.
- Scalability and Flexibility: Each layer can be independently managed and upgraded, allowing for scalability.