In the IKE or IPSec SA rekeying, whether the rekey exchange includes the cryptographic suite in the payload depends on whether the cryptographic suite used in the old SA is changed on both ends, e.g., the initiator and the responder. If the cryptographic suite is not changed, then the rekey exchange does not include the cryptographic suite. Additionally, in the IPSec SA rekey, if the flowing information is not changed in either end, the rekey exchange further does not include the Traffic Selector (TS). As such, the size of the payload is decreased, which saves bandwidth, more processing time and power in the course of the IKE SA or the IPSec SA rekey.