350-501 Automation and Quality of Service Practice Question
An SP engineer implements LLQ for VoIP traffic on a DS3 link. The policy-map calls for a priority queue of 500 kbps. The actual VoIP traffic averages 400 kbps with bursts to 600 kbps. What is the expected behavior during bursts?
⚠ Common exam trap
Cisco often tests the misconception that the priority queue can buffer excess traffic or reclassify it, when in fact LLQ uses a policer to drop traffic exceeding the configured bandwidth to protect other queues.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The priority queue drops all traffic above the configured 500 kbps during the burst.
C is correct because the priority queue in a Low Latency Queueing (LLQ) policy is policed at the configured rate (500 kbps). When VoIP traffic bursts exceed this rate, the excess packets are dropped immediately by the policer, not queued or reclassified. This ensures that the priority queue does not starve other queues and maintains low latency for conforming traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The excess traffic is reclassified to best-effort and placed in the default queue.
Why it's wrong here
No automatic reclassification; drops occur.
- ✗
The priority queue uses tail-drop and discards only when the queue is full.
Why it's wrong here
Priority queue has a policer; drops based on rate, not queue depth.
- ✓
The priority queue drops all traffic above the configured 500 kbps during the burst.
Why this is correct
LLQ polices the priority queue to its configured rate; excess is dropped.
- ✗
The excess traffic is queued in the priority queue until bandwidth is available.
Why it's wrong here
Priority queue is rate-limited; excess is dropped, not queued.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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