Cisco's implementation of the DTLS protocol unfortunately does not
comply with the relevant standards.  OpenSSL must be patched to
provide full compliance with their implementation, and due to the
older release of OpenSSL in the FreeBSD base, there are additional
patches that must be applied to achieve the same goal.  Though
OpenConnect will still function, all traffic will be passed over
an HTTPS connection.  Should there be any packet loss on your
link, your VPN connection will suffer greatly.

More information is included in README.DTLS.