300-420 Question 261
Single answerA network engineer is designing a QoS policy for a branch office WAN link with limited bandwidth. The link will carry VoIP, video conferencing, and general data traffic. The engineer wants to ensure that VoIP traffic has priority over other traffic, while video conferencing receives guaranteed bandwidth, and general data traffic uses remaining bandwidth. Which queuing mechanism is most appropriate for this scenario?
- A
Weighted Fair Queuing (WFQ)
- B
Low Latency Queuing (LLQ)
- C
First-In, First-Out (FIFO)
- D
Class-Based Weighted Fair Queuing (CBWFQ)
Show answer and explanation
Correct answer: B
Explanation
Low Latency Queuing (LLQ) is the most appropriate mechanism for this scenario because it ensures that VoIP traffic receives strict priority for low-latency delivery while providing bandwidth guarantees to video conferencing and allocating remaining bandwidth to general data traffic. This combination ensures that latency-sensitive and bandwidth-intensive applications are handled effectively.
- A. Incorrect.
Weighted Fair Queuing (WFQ) is a flow-based queuing mechanism that provides fairness among flows without strict priority or bandwidth guarantees, making it unsuitable for prioritizing VoIP traffic.
- B. Correct.
Low Latency Queuing (LLQ) combines strict priority queuing (for VoIP) with class-based queuing for other traffic types, making it ideal for scenarios requiring prioritization of latency-sensitive traffic like VoIP.
- C. Incorrect.
First-In, First-Out (FIFO) processes packets in the order they arrive, without any prioritization or bandwidth guarantees. It is not suitable for scenarios requiring differentiated treatment of traffic types.
- D. Incorrect.
Class-Based Weighted Fair Queuing (CBWFQ) allows bandwidth guarantees for traffic classes but does not provide strict priority queuing for latency-sensitive traffic like VoIP, making it less appropriate for this scenario.