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CCNA Voice: QoS Questions
Question 1
Which description describes the low latency queuing algorithm?
A. Empty queue 1. If queue 1 is empty, empty queue 2, then empty queue 3, unless a packet for a higher queue arrives.
B. An administrator defines the traffic classes based on match criteria, including protocols, access control lists, and input interfaces.
C. A flow-based algorithm that simultaneously schedules interactive traffic to the front of a queue to reduce response time and fairly shares the remaining bandwidth among high-bandwidth flows.
D. This feature brings strict priority queuing to CBWFQ.
E. Packets are placed into a single queue and serviced in the order they were received.
Answer: D
Explanation
The Low Latency Queueing feature brings strict priority queueing to Class-Based Weighted Fair Queueing (CBWFQ). Strict priority queueing allows delay-sensitive data such as voice to be dequeued and sent first (before packets in other queues are dequeued), giving delay-sensitive data preferential treatment over other traffic.
Without Low Latency Queueing, CBWFQ provides weighted fair queueing based on defined classes with no strict priority queue available for real-time traffic. CBWFQ allows you to define traffic classes and then assign characteristics to that class. For example, you can designate the minimum bandwidth delivered to the class during congestion.
Question 2
Which description describes the weighted fair queuing algorithm?
A. Empty queue 1. If queue 1 is empty, empty queue 2, then empty queue 3, unless a packet for a higher queue arrives.
B. An administrator defines the traffic classes based on match criteria, including protocols, access control lists, and input interfaces.
C. A flow-based algorithm that simultaneously schedules interactive traffic to the front of a queue to reduce response time and fairly shares the remaining bandwidth among high-bandwidth flows.
D. This feature brings strict priority queuing to CBWFQ.
E. Packets are placed into a single queue and serviced in the order they were received.
Answer: C
Explanation
WFQ is a flow-based queuing algorithm that schedules low-volume traffic first. High-volume traffic shares the remaining bandwidth. Each flow is assigned a weight, where lower weights have higher priority and are serviced first.
WFQ ensures that queues are not starved for bandwidth and that traffic gets predictable service. Low-volume traffic streams comprise the majority of traffic and receive preferential service. High-volume traffic streams share the remaining capacity proportionally.
WFQ never wastes bandwidth. If there’s no higher priority traffic, lower priority traffic is forwarded.
Which description describes the low latency queuing algorithm?
A. Empty queue 1. If queue 1 is empty, empty queue 2, then empty queue 3, unless a packet for a higher queue arrives.
B. An administrator defines the traffic classes based on match criteria, including protocols, access control lists, and input interfaces.
C. A flow-based algorithm that simultaneously schedules interactive traffic to the front of a queue to reduce response time and fairly shares the remaining bandwidth among high-bandwidth flows.
D. This feature brings strict priority queuing to CBWFQ.
E. Packets are placed into a single queue and serviced in the order they were received.
Answer: D
Explanation
The Low Latency Queueing feature brings strict priority queueing to Class-Based Weighted Fair Queueing (CBWFQ). Strict priority queueing allows delay-sensitive data such as voice to be dequeued and sent first (before packets in other queues are dequeued), giving delay-sensitive data preferential treatment over other traffic.
Without Low Latency Queueing, CBWFQ provides weighted fair queueing based on defined classes with no strict priority queue available for real-time traffic. CBWFQ allows you to define traffic classes and then assign characteristics to that class. For example, you can designate the minimum bandwidth delivered to the class during congestion.
Question 2
Which description describes the weighted fair queuing algorithm?
A. Empty queue 1. If queue 1 is empty, empty queue 2, then empty queue 3, unless a packet for a higher queue arrives.
B. An administrator defines the traffic classes based on match criteria, including protocols, access control lists, and input interfaces.
C. A flow-based algorithm that simultaneously schedules interactive traffic to the front of a queue to reduce response time and fairly shares the remaining bandwidth among high-bandwidth flows.
D. This feature brings strict priority queuing to CBWFQ.
E. Packets are placed into a single queue and serviced in the order they were received.
Answer: C
Explanation
WFQ is a flow-based queuing algorithm that schedules low-volume traffic first. High-volume traffic shares the remaining bandwidth. Each flow is assigned a weight, where lower weights have higher priority and are serviced first.
WFQ ensures that queues are not starved for bandwidth and that traffic gets predictable service. Low-volume traffic streams comprise the majority of traffic and receive preferential service. High-volume traffic streams share the remaining capacity proportionally.
WFQ never wastes bandwidth. If there’s no higher priority traffic, lower priority traffic is forwarded.