This object is used to specify a level of
traffic below which the instances of the
cirbhBackHaulRcvdUtilState and cirbhBackHaulSentUtilState
objects are marked as 'acceptable'. All changes to this
threshold will take effect at the end of the current
interval. The value for this object must be less than
the values specified by cirbhBackHaulOverloadedThreshold
and cirbhBackHaulWarningThreshold objects.