cvVoIPCallHistoryFallbackDelay 1.3.6.1.4.1.9.9.63.1.4.2.1.33

The FallbackDelay is calculated as follows - Take the sum of the round trips for all the probes, divide by the number of probes, and divide by two to get the one-way delay. Then add in jitter_in or jiter_out, which ever is higher.