3.2.5.3 Receiving Other Messages
As specified in [RFC3947] section 5.2, NAT-OA payloads can be sent within the first two quick mode messages. On receipt of the first or second quick mode message, the host MUST use the Selected Revision flag of the SA's corresponding entry in the MMSAD to interpret the payload type, as defined in section 2.2.1.
A UDP Encapsulation type can be negotiated through the SA payload, as specified in [RFC3947] section 5.1. On receipt of an IKE message that might contain an SA payload, the host MUST use the Selected Revision flag of the SA's corresponding entry in the MMSAD to interpret the Encapsulation Type, as defined in section 2.2.2.