3.2.1 Abstract Data Model
When this extension is implemented, the following additional state is maintained. This is an extension to IKE Protocol version 1 as specified in [RFC2409].
Main mode security association database (MMSAD): The entry for each MM SA contains the following specific data element for NAT-T:
Selected Revision: A flag that MUST specify what revision of the NAT-T protocol extension (as specified in [RFC3947]) has been selected for this MM SA. For more information, see [DRAFT-NATT].