An advancement over previous techniques using only certain out-of-band probe PDUs to determine loss. Packet loss statistics for a SD-WAN overlay path can be calculated for every packet transmitted by one endpoint and every packet received at the other endpoint. The roles of the positions of circular buffers can be periodically rotated from active to pre-stable to stable to post-stable. Counters in the active role can be incremented whenever a packet is transmitted. A position identifier can indicate which counter to increment when the packet is received. Counters in positions that are stable can be used to produce loss statistics for the SD-WAN overlay path.