esaProbeStatsR2PPkts is a 64-bit performance counter counting the number of test packets sent or received from the reflector back to the probe for the interval that is still being actively collected (the live bin). Comparing the transmitted-versus-received packet counts is how a technician confirms the SLA test itself is actually exchanging traffic before trusting any of the delay or jitter numbers recorded in the same bin. For example, seeing this live count rising steadily bin after bin confirms the probe is still actively generating traffic toward the reflector right now, while a count stuck at zero would mean the test never started; for Y.1731 probes this number is actually a count of Delay Measurement Reply frames, and the P2R and R2P totals are always equal.