Which queuing mechanism establishes four interface output queues that will be used for traffic scheduling?
A.
Priority queuing (PQ)
B.
First-in, first-out (FIFO)
C.
Weighted fair queuing (WFQ)
D.
Custom queuing (CQ)
Explanation:
ExplanationCongestion Management
Two types of output queues are available on routers: the hardware queue and the software queue. The hardware queue uses the strategy of first in, first out (FIFO). The software queue schedules packets first and then places them in the hardware queue. Keep in mind that the software queue is used only during periods of congestion. The software queue uses QoS techniques such as priorityqueuing, custom queuing, weighted fair queuing, class-based weighted fair queuing, low-latency queuing, and traffic shaping and policing.
Priority Queuing
Priority queuing (PQ) is a queuing method that establishes four interface output queues that serve different priority levels: high, medium, default, and low. Unfortunately, PQ can starve other queues if too much data is in one queue because higher-priority queues must be emptied before lower- priority queues.Custom Queuing
Custom queuing (CQ) uses up to 16 individual output queues. Byte size limits are assigned to each queue so that when the limit is reached, it proceeds to the next queue. The network operator can customize these byte size limits. CQ is fairer than PQ because it allows some level of service to all traffic. This queuing method is considering legacy due to the improvements in the queuing methods.Weighted Fair Queuing
Weighted fair queuing (WFQ) ensures that traffic is separated into individual flows or sessions without requiring that you define ACLs. WFQ uses two categories to group sessions: high bandwidth and low bandwidth. Low-bandwidth traffic has priority over high-bandwidth traffic. High- bandwidth traffic shares the service according to assigned weight values. WFQ is the default QoS mechanism on interfaces below 2.0 Mbps.Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 6