QoS question

[jmcgrady1]

I'm applying QoS to a 100mb ethernet link on a Cisco 4431 router.   Say i have a priority queue (realtime) set to use 10% of available bandwidth; then a critical apps queue set to 30% of remaining bandwidth; then other queues spit up the remaining. Realtime is guaranteed 10% of the total and critapps gets 30% of whats left. But what happens when traffic is light? Say realtime is only using 2% at a given time, and critapps 8%. Are the rest of the classes still limited to 60% of total bandwidth? 

[Joseph W. Doherty]

Non-priority classes, by default, get a guaranteed minimum, they can use available/free bandwidth.

Priority classes have an implicit policer which restricts/limits their when there's contention for bandwidth. I.E. they can, sometimes, use more then their class limit, including using 100 percent.