An AVB switch is needed for "audio over network". Otherwise the CS can only control functions like an iPad does. The switch does cost some money (Thomann 309 Euro), but Dante as the only given alternative is much more expensive. And not to forget that Dante always needs a fast and solid computer like a Mac BookPro...
Usually you would connect a dual band router to your AVB switch, so you already have an additional "control of your controller" (was it 10 iPads you can use at the same time?). The CS gives you faders and knobs, but (besides the DAW functions) everything can be handled simultaneously by an iPad at FOH. An iPad at FOH also allows you for example to watch the levels of all auxes or you mix an aux leaving the faders of your CS untouched.
So what would you need the dongle for?
