o  data link error

    An error was reported by the Data Link layer.  Ascertain that
    the query requester function is enabled on the MOP circuit.

 o  unrecognized client

    There is no client with the specified identification.

 o  unrecognized circuit

    There is no circuit with the specified identification.

 o  timeout

    Operation has timed out on the loop command.

 o  entity class not supported (OpenVMS)

    MOP is not registered with EMAA.  The NET$MOP process is
    probably not started.  For instructions on how to restart the
    MOP process, refer to HELP NETWORK_MANAGEMENT MOP.