Access to the headquarters server from the branch computer through the IPsec VPN, at this moment, the IPSEC tunnel can be established normally but business is blocked up, what are the possible reasons? (Select 3 Answers)

Access to the headquarters server from the branch computer through the IPsec VPN, at this moment, the IPSEC tunnel can be established normally but business is blocked up, what are the possible reasons? (Select 3 Answers)
A . The packet is fragmented and the fragmented packet is discarded on the link.
B . There is load sharing or dual-link, may be inconsistent path back and forth.
C . Routing shocks.
D . The DPD detection parameters are inconsistent at both ends.

Answer: ABC