What are the purposes of NAT traversal in IPsec? (Choose two.)

What are the purposes of NAT traversal in IPsec? (Choose two.)
A . To detect intermediary NAT devices in the tunnel path.
B . To encapsulate ESP packets in UDP packets using port 4500.
C . To force a new DH exchange with each phase 2 re-key
D . To dynamically change phase 1 negotiation mode to Aggressive.

Answer: A,B