NSO performs any configuration change as a diff operation against the current configuration. If a device does not support rollbacks, NSO can use the diff engine to calculate the diff between current state and the previous state before the configuration change is applied. NSO knows the capabilities for different network devices and will issue a config change or just a rollback command depending on the network device capabilities. The data models for the devices specify dependencies explicitly as directed references – this ensures that NSO knows in which order to create and delete items.
