350-401 Architecture Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Class-Based Weighted Fair Queuing (CBWFQ)

  Why it's wrong here

  CBWFQ provides weighted fair queuing for each class, but it does not offer a strict priority queue. Voice traffic would be treated with its configured bandwidth weight, which may not be sufficient to meet strict latency requirements. CBWFQ is suitable for data traffic but not for real-time voice that requires priority queuing.

• ✓

  Low Latency Queuing (LLQ)

  Why this is correct

  LLQ combines a strict priority queue with CBWFQ for other traffic. Voice traffic can be placed in the priority queue to ensure minimal delay and jitter, while call signaling and other traffic are handled by CBWFQ with guaranteed bandwidth. This prevents the priority queue from starving other queues because LLQ includes a policer to limit the priority queue bandwidth.

• ✗

  First-In, First-Out (FIFO) queuing

  Why it's wrong here

  FIFO queuing processes packets in the order they arrive, with no prioritization or bandwidth allocation. It cannot provide strict priority for voice traffic, and during congestion, voice packets may be delayed or dropped. FIFO is the default queuing method on high-speed interfaces but is unsuitable for QoS-sensitive traffic.

• ✗

  Weighted Random Early Detection (WRED)

  Why it's wrong here

  WRED is a congestion avoidance mechanism that randomly drops packets before a queue is full. It does not provide priority queuing or bandwidth guarantees. WRED is typically used in conjunction with CBWFQ or LLQ, but it alone cannot ensure voice traffic gets strict priority treatment.