An architect builds a layered design where the enterprise, an industrial DMZ, the supervisory zone, and the basic process control zone are each separated by firewalled conduits. This arrangement primarily realizes the IEC 62443 principle of defense in depth by:

• A.Encrypting only the outermost layer
• B.Concentrating all controls at a single perimeter firewall, a practice anchored in the asset owner's cybersecurity management system under the maturity model
• C.Distributing independent controls across multiple zones so a single breach is contained
• D.Removing the need for component-level security, a designation mapped to the zone and conduit risk assessment methodology in the reference architecture