Active congestion control
To my knowledge codel does not take any parmaters. In OpenWRT's implementation it uses both hfsc and codel. hfsc is used to limit the amount of bandwidth so you have to enter your bandwidth settings manually, and codel is used to shape it.
The problem is that if your internet speed varies through the day you will be limited to the numbers you entered in.
In gargoyle there is active congestion control which pings a host and adjusts the buffer on the router as to not let the ping get too high.
pfsense doesn't require any paramaters to be inputted for codel, so how does it function? E.g how does pfsense know when the buffer is full on the cable modem?