A logistics firm runs voice and bulk backup over a single MPLS transport with variable bandwidth due to carrier policing. The operations team wants per-tunnel queuing plus automatic shaping-rate adjustment when the path degrades. Which QoS treatment on the WAN Edge routers satisfies both needs?

The correct treatment combines per-tunnel egress queuing with closed-loop adaptive shaping because carrier policing makes available bandwidth variable and voice and bulk backup contend differently, so the WAN Edge must maintain separate queues per tunnel for priority and bandwidth fairness while continuously lowering and raising each shaper to the measured path capacity to prevent policer drops and preserve voice quality. Fixed-shaper per-tunnel QoS fails on adaptability because manually provisioned CIR values cannot track policer-induced changes, leaving shapers too high during degradation causing tail drops for voice or too low after recovery causing underutilization. Aggregate adaptive shaping on the uplink fails on granularity because adjusting only the physical port shaper regulates total egress but does not isolate tunnels or guarantee voice versus backup scheduling when one tunnel congests. Per-tunnel QoS with path selection fails on mechanism because moving backup to another path handles steering, not egress rate control, and cannot protect voice that remains on the degraded single MPLS transport. For exams, distinguish adaptive shaping that rewrites shaper rates from routing or SLA-based steering that selects paths, and require both keywords per-tunnel and adaptive for this stem. In practice, validate by congesting the path, confirming measured bandwidth decreases, shaper rates follow, voice queue drops stay near zero while backup is throttled, and policer discards do not spike.