This read-only enumeration reports the specific cause of an ATM SVC port failure -- such as ilmiDown, portDown, vsiOperDown, vccfailure, or neighIpChanged -- but per its own description it exists only as a trap varbind and should never be polled directly with SNMP get or get-next. It gives an admin who receives the associated trap the precise reason an SVC port went down, rather than just the fact that it failed. For example, seeing a trap carrying cwspOperFailReason set to portDown tells the admin the underlying physical port dropped, whereas ilmiDown would point them instead at an ILMI signaling problem on the same port.