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.

• ✓

  Low Latency Queuing (LLQ)

  Why this is correct

  LLQ provides strict priority queuing for delay-sensitive traffic such as voice. It combines priority queuing with CBWFQ. The priority queue is serviced first, and voice traffic is placed in this queue, ensuring it is transmitted before other traffic even during congestion. LLQ also includes a policer to limit the priority queue bandwidth, preventing starvation of other queues.

• ✗

  Class-Based Weighted Fair Queuing (CBWFQ)

  Why it's wrong here

  CBWFQ provides weighted fair queuing for different classes but does not offer strict priority. It allocates bandwidth to each class based on configured weights, but during congestion, all classes are subject to the scheduler, and voice traffic could be delayed. CBWFQ is often used in conjunction with Low Latency Queuing to provide priority, but alone it does not meet the requirement.

• ✗

  Weighted Random Early Detection (WRED)

  Why it's wrong here

  WRED is a congestion avoidance mechanism that randomly drops packets before the queue is full to prevent tail drop. It does not provide strict priority queuing. WRED is typically used for TCP traffic to avoid global synchronization, but it does not prioritize voice traffic. Voice traffic requires strict priority, which WRED cannot provide.

• ✗

  First-In, First-Out (FIFO) queuing

  Why it's wrong here

  FIFO queuing processes packets in the order they arrive, with no prioritization. During congestion, voice packets could be delayed behind large data packets, causing jitter and poor voice quality. FIFO does not meet the requirement for strict priority and is not suitable for delay-sensitive traffic like voice.