Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureMedium
A network engineer is troubleshooting a recently deployed application that uses UDP for real-time video streaming. Users are reporting occasional video stuttering and pixelation, indicating potential packet loss or out-of-order delivery. The engineer suspects that the network's QoS policy might not be correctly prioritizing this traffic. Which QoS mechanism is specifically designed to ensure that critical traffic, like real-time video, receives preferential treatment and is transmitted before other less critical traffic?
- AWeighted Fair Queuing (WFQ)
- BTraffic Policing
- CLow Latency Queuing (LLQ)
- DTraffic Shaping
Show answer & explanationAnswer & explanation
Correct answer: C. Low Latency Queuing (LLQ)
Low Latency Queuing (LLQ) combines the benefits of Class-Based Weighted Fair Queuing (CBWFQ) with strict priority queuing for specific traffic classes. This ensures that delay-sensitive traffic, such as real-time video and voice, is dequeued and transmitted first, minimizing latency and jitter.
Why the other options are wrong
- A. Weighted Fair Queuing (WFQ) provides fair bandwidth allocation but does not offer strict priority for critical traffic, meaning real-time video could still experience delays.
- B. Traffic Policing drops or re-marks packets that exceed a configured rate, which can contribute to packet loss and is not about preferential treatment.
- D. Traffic Shaping buffers excess traffic, delaying it rather than prioritizing its immediate transmission.
Low Latency Queuing (LLQ)
A QoS queuing mechanism that provides strict priority to delay-sensitive traffic within an output queue, ensuring it is transmitted before other traffic.
- Combines CBWFQ with strict priority queue.
- Ideal for voice and video (real-time applications).
- Minimizes latency and jitter for prioritized traffic.
- Guarantees bandwidth and low delay for critical applications.
Memory trick: Queues: Prioritizing packets for smooth sailing.