In NADAC ASIO Panel, make sure you dont' have a "Network Throttling" error message.
Windows can automatically reduce the network bandwidth on some specific process.
The NADAC ASIO installer should turn off this option automatically (and tells you that this setting has been modified), but if for any reason this option has been turned on, you may disable Network Throttling on your system, by downloading this patch :DisableNetworkThrottling.zip then un-zip and launch the .reg file.
Restart your computer after applying the patch.
See as well Network Throttling