3.4.7.1 Invalid Message Received
If an invalid message is received, the initiator MUST send a NOTIFY_STATUS Notify payload and delete its SA state for this negotiation.
The message MUST be constructed as follows:
HDR: The ISAKMP header MUST be identical to the IKE Informational packet, as specified in [RFC2409] section 5.7, and the exchange type MUST be 246 (NOTIFY exchange type).
Notify (Status): This notify MUST have the RELIABLE_NOTIFY_FLAG, as specified in section 2.2.3.5, set to TRUE.