Software-defined networks (SDN): an architectural approach that optimizes and simplifies
network operations by more closely binding the interaction (i.e., provisioning,
messaging, and alarming) among applications and network services and devices, whether
they be real or virtualized. It often is achieved by employing a point of logically
centralized network control—which is often realized as an SDN controller—which then
orchestrates, mediates, and facilitates communication between applications wishing to
interact with network elements and network elements wishing to convey information