QoS on pvc or virtual interfaces

Question

Suppose you have some pvc configured on a physical interface, or some subinterfaces, point-to-point with an associated pvc.
All the traffic comes out from the same physical interface, so same buffer and hardware queue for all pvcs.
If you send all voip traffic using one pvc, interactive traffic with anether pvc, best-effort traffic with another pvc, how can you reserve bandwidth for different classess ?
I mean, how can you be sure that voice pvc will be dequeued before others pvc ?

Answer 1

"If you send all voip traffic using one pvc, interactive traffic with anether pvc, best-effort traffic with another pvc, how can you reserve bandwidth for different classess ? "
If using CBWFQ, first, insure your PVCs' bandwidths don't oversubscribe the physical interface bandwidth. Second, enforce the PVCs bandwidth allowances. (For FR, can be done with shapers, for ATM, can be done by the hardware.)
You might also want dedicated PVCs for real-time traffic so that your CIR is the same as the expected real-time traffic demand.
PS:
I also recall there's a technique to use a special two level queue for FR to insure multiple PVCs real-time traffic always goes first, but I haven't used that feature.