DDNS methods include: sending username password and domain in the clear; and "direct-URL" method where a token is sent from the gateway and automatically picks up the source IP. 

Why doesn't TP-LInk support the direct-URL method? 

I use afraid/OpenDNS and it would be much easier and more secure to support this (quite easy) method, under custom as an option, or just add an entry of "Direct URL Custom"

I don't like exposing my OpenDNS password in the DDNS access.