This read-create object holds the index of the corresponding entry in the standard atmTrafficDescrParamTable. It's the glue tying this Cisco-specific frame-relay traffic descriptor row to the standard MIB-II table the ATM signaling stack actually enforces against, so a stale or mismatched index here means the two tables can disagree about a connection's real traffic contract even though this table's own CIR and PIR values look correct. If this index points to an atmTrafficDescrParamTable row that has since been deleted, the switch may enforce different, stale traffic parameters than what casfTrafficDescrCIR and casfTrafficDescrPIR here suggest.