IPv6 has embedded support for IPsec (a common
protocol for encryption). Currently the host operating
system (OS) can configure an IPsec tunnel
between the host and any other host that has IPv6
support. With IPv4 the vast majority of IPsec
deployments are network-based and unknown to
host devices. With IPv6 IPsec, the host could create
an encrypted data connection between itself and
another device on the network. This means that
network administrators do not need to set up the
encryption, because hosts can do it themselves on
demand.