A Software-Defined Network (SDN) controller receives controller Application Programming Interface (API) calls from an SDN application and transfers SDN data machine API calls. SDN data machines receive the SDN data machine API calls and process user data responsive to the SDN data machine API calls. The SDN controller transfers SDN controller Key Performance Indicators (KPIs) that indicate an amount of the SDN application API calls for the SDN data machine API calls. The SDN data machines transfers SDN data machine KPIs that indicate an amount of the processed user data for the SDN data machine API calls. An SDN server receives the SDN data machine KPIs and the SDN controller KPIs. The SDN server determines an SDN Quality-of-Service (QoS) score for a data communication service based on the amount of the SDN application API calls relative to the corresponding amount of the processed user data.