UTT Technologies
Chapter 10 VPN
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9.5.1.7 Packet Flow – IPSec Initiator
Figure 11-16 IPSec Packet Flow
As shown in
Figure 11-16 IPSec Packet Flow,
during the IPSec tunnel establishment and
data transmission processes, the packet flow through the IPSec initiator can be
summarized as follows:
1. After the IPSec tunnel parameters are configured properly, the new policy is added
into the SPD (1) in.
2. The initiator receives a packet that matches an IPSec policy in the SPD (3) .
3. IKE phase 1 negotiation takes place (started by the initiator), and the IKE SA is
established (4). Refer to section 4.2.1.3 for more information.
4. IKE phase 2 negotiation takes place, and the IPSec SAs are established (5) The
initiator uses ESP and/or AH to protect the user data (i.e., original packets) (6)
5. The initiator sends the IPSec packets to the responder through the IPSec tunnel (7)
The initiator receives the IPSec packets from the responder, and authenticates and/or
decrypts them (12).
6. The initiator forwards the user data (i.e., original packets) to their intend destinations
(13).
7. The two endpoints renegotiate IPSec SAs as required (14). Refer to section 4.2.1.4
