A、 To ensure the router has the correct time when generating its private/public key pairs.

B、 To ensure the router has the correct time when checking certificate validity from the remote peers

C、 To ensure the router time is sync with the remote peers for encryption keys generation

D、 To ensure the router time is sync with the remote peers during theDH exchange

E、 To ensure the router time is sync with the remote peers when generating the cookies during IKE phase 1