SQM - What is the difference between diffserv3 (default) and diffserv4 for layer_cake?

What is the difference between diffserv3 (default) and diffserv4 for layer_cake?

I noticed that diffserv4 is adding another tier called video.
Does it mean that Netflix and YouTube will be working better or is video meaning more like video chat?

Thanks.

more like video chat.

This might help you.