Specifies whether each IKE phase 2 negotiation will employ Perfect Forward Secrecy (PFS), and if yes, which Diffie-Hellman group to employ. PFS ensures that even if someone were to discover the long-term secret(s), the attacker would not be able to recover the session keys, both past and present. In addition, the discovery of a session key compromises neither the long-term secrets nor the other session keys.