300-415 Question 257
Single answerAn enterprise has deployed Cisco SD-WAN to support their critical applications. The network administrator wants to ensure that voice traffic is prioritized over less critical traffic during congestion. Which queuing mechanism should be implemented on the SD-WAN edge devices to meet this requirement?
- A
Weighted Fair Queuing (WFQ)
- B
Low Latency Queuing (LLQ)
- C
Random Early Detection (RED)
- D
Class-Based Weighted Fair Queuing (CBWFQ)
Show answer and explanation
Correct answer: B
Explanation
Low Latency Queuing (LLQ) is the optimal choice for prioritizing voice traffic in a Cisco SD-WAN deployment. LLQ combines Class-Based Weighted Fair Queuing (CBWFQ) with a strict priority queue, ensuring that delay-sensitive traffic, such as voice, is transmitted first, even during network congestion, thereby reducing latency and jitter. Other queuing mechanisms, such as WFQ and CBWFQ, lack the strict priority feature, while RED focuses on congestion avoidance rather than traffic prioritization.
- A. Incorrect.
WFQ dynamically allocates bandwidth among flows based on weights but does not guarantee low latency for critical traffic like voice.
- B. Correct.
LLQ is designed to prioritize delay-sensitive traffic, such as voice, by providing a strict priority queue, ensuring minimal latency and jitter during congestion.
- C. Incorrect.
RED is a congestion avoidance mechanism that drops packets probabilistically to prevent buffer overflow but does not prioritize specific traffic types.
- D. Incorrect.
CBWFQ provides bandwidth guarantees for traffic classes but does not include a strict priority queue for latency-sensitive traffic like voice.