With this beta firmware, you cannot set any of the DoS attack prevention setting types under Security except for TCP Xmascan. Once you click apply, and then go save the updated configuration and return, everything but Xmascan remains marked in the GUI as disabled. This persists thru a logoff/logon sequence as well.
Hardware rev B2 here, DGS-1100-16. Firefox 56.0.2 on MacOS X and Safari 11.0 both exhibit same GUI behavior.
I was able to contact D-Link US support and get a more recent B043 firmware that corrected the original issue I had, plus removed this particular regression. You guys should refresh this link to a firmware without any significant regressions between B036 and B043.