The IoTSI Reference Architecture is part of the IoTSI Framework for securing IOT/IIOT Infrastructures and Applications.The IoTSI Security Reference Architecture provides a tangible, deployment driven, pragmatic framework for designing and deploying a secured IIoT/IoT Architecture.The Reference Architecture Documents is based on 5xTiers of Cyber Defense tactics: Stage-1 – Inhering/Embedded Security Capabilities. Stage-2 – “Standard” OT/ICT Information Security and Cyber Defense solutions & Technologies (e.g, ALG, NGNS, EPP, etc’). Stage-3 – Advanced Cyber Security Technologies (e.g. Analytics, Automation, Zoning, etc) Stage-4 – IOT/IIOT Native Cyber Security Technologies – Unique, Pure-play concepts design especially for Critical IOT/IIOT/IC Stage-5 – Operational Security