Thus spake "Christos Papadopoulos" <christos@CS.ColoState.EDU>
I know routers today have the ability to prioritize traffic, but last I heard, these controls are not often used for user traffic (let's not discuss net neutrality here).
They're not often used on _public_ networks for user traffic. They're used extensively on _private_ networks, though, because the people paying the bills for network do so for a particular business purpose and they want to make sure it's met.
Are they used for control (e.g., routing) traffic?
Many routers automatically put control traffic to/from the local node into a separate path that completely bypasses the standard queueing mechanisms (and predates operator-accessible QOS). In other routers, the control plane and forwarding plane are segregated, which achieves the same goal but with a rather different approach. S Stephen Sprunk "Those people who think they know everything CCIE #3723 are a great annoyance to those of us who do." K5SSS --Isaac Asimov