All downlink communication is requested on and managed by the Actuator API. Optionally a Destination can request and manage downlink communication as well.
After a downlink is requested on the Actuator API it is encoded. Meaning the downlink is translated to a message the device will understand. After encoding the downlink is send over the selected network to your device.
The network (and the device) will report feedback about the delivery of the downlink to the Actuator API. This information can be retrieved by the application, or the Things Connector fetches this information into your system.