Hmm, you talked to some engineers and they told you that until MPLS and DiffServ are implemented throughout the entire Internet, nobody's performance will be improved by tagging packets for priority service, but others will be slowed down? That's an interesting analysis, for sure. Perhaps you could find somebody willing to make it public, and you know, stand behind it; maybe they could even show some data, so it wouldn't be "my daddy says your daddy is a dummy." Intuitively, DiffServ reduces jitter at each hop in a stream. If a stream has it all hops, under load his jitter is dramatically reduced. If the stream crosses 15 hops, and only 10 observe DSCP but they all preserve the markings, then the stream still gets a measurable improvement under load. There's no need for the routers managing a hop with low mean latency to observe DSCP, as the bandwidth will keep the queue size low. There are commercial enterprises selling low-jitter service to commercial Internet customers today: Verio and WebEx are two I've used, and their customers are happy. According to your anonymous engineers, that's impossible. Thanks, but I'll believe my lying eyes. PS: The Internet is a packet-switched network.