Question 440
A WAN QoS filter counts packets by packet-loss priority. Observed: Policer counters rise but the wrong loss-priority bit is set internally. What operational check best guards against this problem returning?
Explanation
Correct Answer
This control asks for the same recovery evidence (Internal class and loss-priority counters match the policy for each sample flow) and flags recurrence of the same failure (Policer counters rise but the wrong loss-priority bit is set internally). It targets the underlying issue, the policy sets a forwarding class but omits the packet-loss priority action, rather than a different service problem. The exact cadence must be agreed with operations.
Incorrect Answers
This gate monitors a different failure, a new customer receives the same bandwidth guarantee as the largest existing customer. It would not detect the current problem: Policer counters rise but the wrong loss-priority bit is set internally. The appropriate check requires internal class and loss-priority counters match the policy for each sample flow.
It is valid for another service scenario but checks premium traffic is delivered as best effort because the incoming label class is not decoded. This case instead needs a gate for policer counters rise but the wrong loss-priority bit is set internally and evidence that internal class and loss-priority counters match the policy for each sample flow.
The proposed control is tied to a dscp classifier is not bound to the ingress traffic interface, typically observed when traffic with a valid voice DSCP enters the default best-effort queue. Here the target is the policy sets a forwarding class but omits the packet-loss priority action; monitor internal class and loss-priority counters match the policy for each sample flow.