Which statement about APIC controller versus a more traditional SDN controller is true?

APIC employs a declarative model where administrators define policies expressing desired network behavior, and policy agents distributed on ACI leaf and spine nodes autonomously translate those policies into low-level forwarding instructions. This differs fundamentally from traditional SDN controllers such as OpenFlow-based systems, which push explicit, imperative configuration commands directly to each device.

OpFlex is the Southbound protocol APIC uses to communicate policies down to ACI fabric nodes, not a Northbound protocol; the Northbound interface toward operators and applications uses REST API.

REST API is APIC's Northbound interface used by operators and orchestration tools; APIC does not use a REST API as a Southbound protocol toward ACI switches - that role belongs to OpFlex.

APIC uses a declarative (policy-driven) model, not an imperative one; imperative models specify exact step-by-step device instructions, which characterizes traditional CLI management and protocols like OpenFlow.