Retries and acknowledgments

Zigbee includes acknowledgment packets at both the Mac and Application Support (APS) layers. When data transmits to a remote device, it may traverse multiple hops to reach the destination. As data transmits from one node to its neighbor, an acknowledgment packet (Ack) transmits in the opposite direction to indicate that the transmission was successfully received. If the transmitting device does not receive the Ack, it retransmits the data up to four times. This Ack is called the Mac layer acknowledgment.

In addition, the device that originated the transmission expects to receive an acknowledgment packet (Ack) from the destination device. This Ack traverses the same path that the data traversed, but in the opposite direction. If the originator fails to receive this Ack, it retransmits the data, up to two times until an Ack is received. This Ack is called the Zigbee APS layer acknowledgment.

Note Refer to the Zigbee specification for more details.