QoS/CoS services are best when clearly spelled out in service agreements. Providers may clear markings, but likely because either they don't want to have a free for all when it comes to their queues, or because they didn't purchase the gear that offers the rich queuing needed.
If those flags provide better quality of service, why am I not applying them to all of my traffic? Any attempt to "know" if my use is legitimate would undermine network neutrality.
Sure, you could make yourself crazy trying to prioritize all the traffic with varying kinds of flags.
Or you could just let an algorithm (SQM - fq_codel or cake) automatically determine which flows are sending more than their fair share of traffic into the bottleneck link, and offer backpressure to slow those applications down, so other applications work well.
re: net neutrality. That applies to whether my ISP (or any provider upstream in the Internet) should prioritize packets/data from various sources toward (or from) me. The answer should be, No. My contract with my ISP is that I get X mbps of data. The contract doesn't say the ISP will provide higher priority or data rate for service Y over service Z...
SQM has no effect on net neutrality: I'm simply configuring my own router to prioritize the data that I'm requesting (or sending). My ISP should handle them in a totally neutral way...
QoS/CoS services are best when clearly spelled out in service agreements. Providers may clear markings, but likely because either they don't want to have a free for all when it comes to their queues, or because they didn't purchase the gear that offers the rich queuing needed.