The maximum ingress trip time standard deviation allowed over the
course of any test. If the calculated standard deviation of the
ingress trip time at the end of any test exceeds this threshold,
a jnxPingIngressStddevThresholdExceeded trap will be sent.
This applies only if the probe type (pingCtlType) provides one way
delay measurements. Currently jnxPingIcmpTimeStamp is the only
supported probe type with this property.