I've NEVER changed the QOS because I found that the stock settings work very well. There are long discussions and even entire web pages about this area. Let's check out the recent question at CNET at http://forums.cnet.com/7723-7583_102-571019/video-streaming-problems-who-s-to-blame-isp-or-computer/?tag=contentBody;threadListing
You find that folk are all over the map on this one. It's a simple problem since you have HOW MANY VENDORS INVOLVED? I see Samsung, Cisco, Comcast as well as the streaming suppliers without any one to pull it all together.
It's like it's a beta and with folk used to how well cable and such TV worked, they may not understand that all this is not for those that will put up with the issues.
I've lost count of the causes over the past few years but try anyway when folk ask. But first, it's not a sure thing. If folk can't accept that, I can't offer much else.
Many of the settings we want to try are over in the CNET Networking Forum. We know to try the router defaults, then turn off the wifi for a test run.
I have a UN60D7000 Smart TV, a comcast broadband 30 mbsp, Cisco EA45000 router and the QOS set to the TV's MAC address as the highest priority. I still can't get HuluPlus, Netflix or HBOGO to play without constant start and stop buffering. Samsung has been of no help yet - just doing the old reset the Hub routine to no avail. Any suggestions? Streaming these apps is the reason I bought this model.