1. This is being measured as part of our UDP protocol metrics in layer 4 in the source and in the destination
2. Let us say UDP protocol at source node A sends a datagram. At the MAC - WLAN send the frame and starts a re-transmission timer.
3. If not Ack is received within this timer period it would initiate a re-transmission (consider cases where the WLAN Ack has a collision or is errored)
4. As the destination the MAC (WLAN) layer would send up to UDP both the first packet it received and the re-transmitted packet it received.
5. UDP protocol in the destination would count both the packets received