Class A (Default): Bi-directional devices
Completely uplink oriented. Uplink transmission is followed by two receive slots. Downlink transmissions are queued in network until next uplink creates two receive slots. Radio sleeps the rest of the time and battery is preserved. Note that the network cannot send a downlink until the device wakes up (triggered by an event on the device like a timer or a sensor threshold)
Class C (Continuous): Bi-directional devices with maximal receive slots
Device never sleeps, but always listens between uplinks. The device is always available for downlink, but batteries are drained. Not feasible on battery only.
Class B (Beacon): Bi-directional devices with scheduled receive slots
Extension on class A, device opens extra receive windows at scheduled times indicated by beacons transmitted by the network. [color=red]Currently not supported. Class B is not yet specified fully by the LoRa Alliance, KPN will include class B after full specs are available[/color]