1
Understand the environment
Stakeholder listening, context analysis, operational constraints, critical assets and dependencies.
Approach
A structured, independent and field-oriented method
Reducing risk without disconnecting architecture from real operational constraints or business priorities.
IT/OT Architecture
From field to cloud — IT/OT levels through the Purdue Model
The Purdue Model structures the levels of an IT/OT architecture — from the electromechanical layer (EPO) up to enterprise systems and the cloud, with a demilitarized zone (DMZ) as the security boundary between OT and IT.
2
Synthesize requirements and constraints
Connecting business needs, technical limits, risks, budgets and field feasibility.
3
Design for sustainability
Defining segmented, secure, maintainable, documented and scalable architectures.
4
Support, train and transfer
Team support, targeted training, knowledge transfer and clear, usable, audit-ready documentation.
Frameworks
Recognized models, adapted to field realities
Standards and models should not be applied as simple checklists. RĒSUNIX adapts them to real constraints: real-time performance, availability, legacy systems, maintenance, supplier access, segmentation, governance and operational continuity. The frameworks listed here are the most common — other sector-specific, regulatory or organization-specific frameworks may apply depending on the mandate.
NIST SP 800
Publications for cybersecurity and risk management, including SP 800-82 for OT.
Purdue model
Structuring levels, zones, conduits and flows between IT and OT environments.
ISA/IEC 62443
Best practices for securing industrial automation and control systems.
ITSG (Canada)
Canadian guidance applicable to risk, controls, wireless, telecommunications and sensitive systems.