What is OT architecture?
OT architecture (Operational Technology architecture) describes the structure, coherence and operation of the systems, networks and processes that control and monitor physical processes in the real world. It includes SCADA systems, PLCs, Sensors, Actuators, industrial networks and monitoring tools — and their integration with IT systems.
OT architecture ensures reliable, safe and manageable process automation, from the field layer up to management level.
🧱 Typical components of OT architecture
| Component | Description |
|---|---|
| PLCs and RTUs | Control and monitor physical processes (pumps, valves, motors) |
| SCADA/HMI systems | Central monitoring and control of processes |
| Industrial networks | Protocols such as Modbus, Profibus, Profinet, Ethernet/IP and OPC-UA |
| Sensors and actuators | Measurement and control points in the field |
| Historian databases | Storage of time-series and measurement data for analysis |
| Edge and IoT platforms | Local processing and filtering of data for OT/IT integration |
🏗 OT architecture in layers (Purdue model)
A common way to structure OT architecture is through the Purdue model:
| Level | Description |
|---|---|
| Level 0 | Physical process (water, electricity, traffic, production) |
| Level 1 | Sensors, actuators, field devices |
| Level 2 | Control: PLC, DCS, IEDs |
| Level 3 | Monitoring and supervision: SCADA, Historian, HMI |
| Level 3.5 | DMZ / secure separation from the IT network |
| Level 4 | IT: MES, ERP, analytics, business systems |
A good OT architecture defines which components, protocols and security measures apply at each level.
🔐 Security considerations
| Security measure | Explanation |
|---|---|
| Network segmentation | Separate zones (field, SCADA, IT) using firewalls and VLANs |
| Security by Design | Build security directly into the architectural design |
| IEC 62443 | Standard for OT security and zones/conduits |
| Patch management | Safe and controlled updating of firmware and software |
| Lifecycle Management | Versioning, documentation and end-of-life policy for OT components |
| Logging and detection | Monitoring abnormal behaviour or unauthorised access |
🔁 Differences between IT and OT architecture
| Feature | IT architecture | OT architecture |
|---|---|---|
| Purpose | Information management, user support | Process control, physical execution |
| Priority | Confidentiality > availability | Availability > integrity > confidentiality |
| Frequency of change | High (patches, updates) | Low (long lifespan, planned maintenance) |
| Interfaces | User applications, web services | Sensors, actuators, machine protocols |
OT convergence calls for an architecture that connects both worlds technically and in terms of policy.
🧭 Aims of OT architecture
- Standardising components and networks
- Manageable growth of installations
- Safeguarding safety and availability
- Promoting interoperability between vendors and systems
- Preparing for innovation (e.g. IIoT, predictive maintenance)
📌 In summary
OT architecture is the blueprint for reliable, safe and future-proof industrial systems. By bringing structure to control, networks and security, OT becomes manageable as a whole — also in conjunction with IT.
See also OTArchitect.nl