RFC: Ipsec support in main

[Aitor]

My point of view is that IPSec will become much more popular in IPv6
deployments where NAT is not used, as IPSec is mandatory in IPv6
compliant devices. OpenVPN is a good solution for road warriors because
it deals fine in NAT environments and it's independent from
infrastructure's capabilities. But I think IPSec is more convenient if
NAT doesn't play and device's support is guaranteed.