What scenario does the term "active/standby" refer to in the context of SDN controllers?

The term "active/standby" in the context of SDN (Software Defined Networking) controllers primarily refers to a high-availability setup. In such a configuration, one controller operates actively while another is on standby, ready to take over in case the active controller fails or becomes unavailable. This ensures continuity of service and minimizes downtime, which is crucial for maintaining network reliability.

In a high-availability scenario, the standby controller is constantly synchronized with the active one, maintaining up-to-date state information so that it can seamlessly assume control without significant interruption. This approach is vital in networks where uptime is critical and can significantly improve resilience against various failures, thereby enhancing overall network stability and performance.

Other scenarios like load-balanced architectures, modular designs, and centralized management systems do not fundamentally fit the definition of an active/standby setup, as they involve different operational approaches to managing resources and traffic across the network.