NAC Foundational Device Visibility and Control for IT/OT Convergence Share this: Published: 1 Feb 2019 Historically, the focus of network access control (NAC) has been Authentication, Authorization, and Accounting (AAA). At its core, NAC enables mobility and dynamic security. However, the enterprise network no longer sits within four secure walls. It extends to wherever employees and data travel. Mobility, digitization, and the IoT are changing the way organizations operate.