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352-001 · Question #207

What are two potential effects of increasing the percentage of priority traffic? (Choose two.)

The correct answer is A. can increase latency and jitter for priority traffic B. can increase latency and jitter for non-priority traffic. Increasing the percentage of priority traffic can degrade performance for both priority and non-priority traffic when the priority queue becomes overloaded or bandwidth is exhausted.

Design Considerations

Question

What are two potential effects of increasing the percentage of priority traffic? (Choose two.)

Options

  • Acan increase latency and jitter for priority traffic
  • Bcan increase latency and jitter for non-priority traffic
  • Cmakes it impossible to bound the impact that priority traffic will have on non-priority traffic
  • Dmust be avoided regardless of traffic patterns
  • Ewill not ever change the performance of non-priority traffic

How the community answered

(24 responses)
  • A
    75% (18)
  • C
    17% (4)
  • D
    4% (1)
  • E
    4% (1)

Why each option

Increasing the percentage of priority traffic can degrade performance for both priority and non-priority traffic when the priority queue becomes overloaded or bandwidth is exhausted.

Acan increase latency and jitter for priority trafficCorrect

When priority traffic is increased beyond the configured policing rate or the scheduler's capacity, the priority queue itself can become saturated, causing packets within it to experience queuing delay and variable jitter.

Bcan increase latency and jitter for non-priority trafficCorrect

As priority traffic consumes a larger share of available link bandwidth, the remaining bandwidth for non-priority classes is reduced, forcing those queues to build up and increasing their latency and jitter.

Cmakes it impossible to bound the impact that priority traffic will have on non-priority traffic

LLQ (Low Latency Queuing) with priority policing is specifically designed to cap priority traffic and thereby bound its impact on non-priority classes, making it possible - not impossible - to control this effect.

Dmust be avoided regardless of traffic patterns

Avoiding priority traffic entirely is not a valid design principle; voice and video applications require strict priority queuing to meet latency and jitter requirements.

Ewill not ever change the performance of non-priority traffic

Non-priority traffic performance is directly dependent on the bandwidth remaining after priority traffic is served; increasing priority traffic necessarily impacts non-priority performance.

Concept tested: LLQ priority queue bandwidth effects on QoS

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_conmgt/configuration/xe-16/qos-conmgt-xe-16-book/qos-conmgt-oview.html

Topics

#priority queuing#QoS#latency#jitter

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