The SnmpUsmProxy object inherits from SnmpProxy. When a request is received, the translateParameters() method is called.
If the request is an SNMPv1 or SNMPv2 request, the security level is set to noAuthNoPriv. If the received community string is of the form community@contex, the context name is set to the received context value. If it is in any other form it is null.
If the request is an SNMPv3 request, the received context, security level, and other values are reused.