The value of msapAtmPlcyOamPeriodicLoopback specifies if the MSAP will run periodic OAM loopbacks. If enabled, an ATM OAM loopback cell will be transmitted every period as configured in tAtmSysOamLoopbackPeriod; if a response is not received and tAtmSysOamRetryDown consecutive retries also result in failure, the endpoint will transition to the eteAisLoc state; once in the eteAisLoc state, an ATM OAM loopback cell will be transmitted every period as configured in tAtmSysOamLoopbackPeriod; if a response is received for the periodic loopback and tAtmSysOamRetryUp consecutive retries also each receive a response, the endpoint will transition back to the up state.