"The packet loss and retransmission data is gathered directly from the NIC driver operating on the AMD." Since the data is duplicated to AMD it would simply need to track the packets that it is seeing in order to determine the number of lost packets and retransmissions.
For more information, you can look at this report and description: https://community.dynatrace.com/community/display/DCRUM124/AMD+global+packet+stats
Thanks for the response, just curious to know what happens when packet lost during duplication on AMD, then this network packet would not be available on AMD for analysis . Does this impact the overall rate of retransmission detected in DCRUM reports.
The duplication is done through a tap or a span on the network and is sometimes dispersed by a port aggregator like Gigamon. The AMD usually just receives the output from these methods. I would assume that if a packet is lost, it would be lost to both the AMD and the intended server as they are usually in the same data center. At this point the intended server would be sent a retransmission and in turn, so would the AMD. In the case that the AMD alone doesn't receive the packet, I don't think we request a retransmission as this is simply the monitoring tool, it would most likely just increase the packet loss count.