I'm having problems with viber when I'm connected to wifi and the other party that called me is via wifi also. I've set the ports of viber on QOS and it's working flawlessly if my synology nas is not downloading anything. but if I'm downloading, the problem is I get poor audio to almost no audio for both of us. but when someone called me and is using 3g/4g connection, the connection is excellent even when I'm downloading on my nas. I don't have this problem with skype only in viber. btw, I tested it with my friend who's also using tomato fw. I configured his router just like my settings. could it be my ISP? (we have the same ISP) Here's the screenshot of my QOS.