SnmpEngineIdOrNone
A specially formatted SnmpEngineID string for use with the Entity MIB. If an instance of an object of SYNTAX SnmpEngineIdOrNone has a non-zero length, then the object encoding and semantics are defined by the SnmpEngineID textual convention (see STD 62, RFC 3411 [RFC3411]). If an instance of an object of SYNTAX SnmpEngineIdOrNone contains a zero-length string, then no appropriate SnmpEngineID is associated with the logical entity (i.e., SNMPv3 is not supported).