Interesting. And disturbing. I actually called ZyXEL U.S. support about it and was told, very specifically, "Check the box. That's all there is to do and all you can do."
That said, I did set the inbound and outbound speeds as well. We really, really need to get to a point where we have across the board QoS for things, like SIP/VoIP, that need it.
BranoI hate VogonsPremium,MVM
Yes, checking the box and setting the WAN interface speeds should be enough for SIP only. For other services you need to do it manually as per my earlier example thread.