esaProbeHistorySumOfSqAbsR2PJitter is a 64-bit performance counter that reports the sum-of-squares of the absolute-value one-way jitter (magnitude of the delay swing regardless of direction), in microseconds, from the reflector back to the probe, applicable to Layer 3 ICMP-timestamp and Layer 2 Y.1731 probes, for a completed interval that has already closed and been archived into the rolling history log. Because it discards the sign of the swing, this absolute-jitter figure from the reflector back to the probe gives a technician a single severity number to alarm on without watching the positive and negative jitter counters separately. For example, a technician investigating a resolved outage can combine this archived sum-of-squares value with the stored sum and count to reconstruct the variance of absolute jitter from the reflector back to the probe during the incident window, long after that bin closed.