OT Networks and Segmentation

Physical layer, addressing, segmentation and the security boundary between plant and enterprise. The layer blamed for everything and instrumented for nothing.

Where this sits

This is ISA-95 Level 3-4. Naming the layer matters, because the most expensive mistakes in modernization come from solving a problem at the wrong level of the stack.

What we actually do here

• Assess what is installed, what version it is on, and what depends on it
• Decide what to modernize, in what order, and what to deliberately leave alone
• Write scope and acceptance criteria that a vendor cannot quietly reinterpret
• Review design and code before commissioning, not after
• Make sure the plant can support the result once the project team has gone

Platform position

Vendor-independent, but not opinion-neutral. When one platform is clearly better for a given situation, we will say which and why. When the honest answer is that the existing system is fine and the money is better spent elsewhere, that is the recommendation.