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Cisco's implementation of the DTLS protocol unfortunately does not
comply with the relevant standards. OpenSSL 0.9.8m or newer, and
1.0.0-beta2 or newer, contain a compatibility mode which allows
interoperation with Cisco's servers.

As long as you are using a current version of OpenSSL, you have nothing
to worry about -- everything should work optimally.

Without a suitable OpenSSL, the openconnect client will fall back to
passing packets over the HTTPS connection. This will still work OK, but 
will suffer quite a lot if your connection has packet loss. For details
of why that happens, see http://sites.inka.de/~W1011/devel/tcp-tcp.html

If you insist on using ancient buggy versions of OpenSSL, these are the
patches you require if you want DTLS to work:

For versions of OpenSSL earlier than 0.9.8m, you'll need the Cisco
compatibility support:
	http://cvs.openssl.org/chngview?cn=18037

For versions of OpenSSL earlier than 0.9.8j, a couple of other DTLS
bug-fixes are also required:
	http://cvs.openssl.org/chngview?cn=17500
	http://cvs.openssl.org/chngview?cn=17505