The time when this row was created.
This object is the second index of the
rttMonStatsCaptureTable Table.
The the number of rttMonStatsCaptureStartTimeIndex
groups exceeds the rttMonStatisticsAdminNumHourGroups
value, the oldest rttMonStatsCaptureStartTimeIndex
group will be removed and replaced with the new entry.
When the RttMonRttType is 'pathEcho', this object also
uniquely defines a group of paths. See the
rttMonStatsCaptureEntry object.