Erik Auerswald pointed me to an interesting open-source project. LibreQoS implements decent QoS using software switching on many-core x86 platforms. It’s implemented as a bump-in-the-wire software solution, so you should be able to plug it into your network just before a major congestion point and let it handle the packet dropping and prioritization.

Obviously, the concept is nothing new. I wrote about a similar problem in xDSL networks in 2009.