Purdue model OT-IT architecture integrating five automation levels (L0–L4) with segregated security zones for thermal power generation, electrical distribution, utilities, and building automation. Data flows from field sensors and PLCs through local supervision (L2) and OT engineering (L3) layers, with enterprise IT (L4) connectivity via firewalls and VPN peers to external partners including INNIO, RABA, and DunaIS. This defense-in-depth design isolates critical control systems from corporate networks while enabling remote monitoring through Vision SCADA, Honeywell HMI, and historian databases. Fork and customize this diagram to model your own industrial facility's OT-IT segmentation, firewall rules, and data historian placement. The architecture demonstrates best practices for critical infrastructure protection, including air-gapped L0–L1 zones, DMZ-style L3 supervision networks, and managed external access through S2S VPN and external firewalls.