The maximum OAM ping round-trip-time (RTT) received.
A value of 0 for this object implies that no RTT has been received.
This value is relevant when tmnxOamPingCtlTestMode has a value of
'sdpPing', 'ethCfmLoopback', 'ethCfmTwoWayDelay', or 'ethCfmTwoWaySlm'.
Otherwise, this object contains a value of 0.