300-430 · Question #295
An engineer configures QoS on an AireOS WLC v8.5. The engineer configures a WLAN for voice traffic and must set the data rates within the QoS profile. How should the data rates be configured to ensure
The correct answer is B. The burst data rate should be greater than or equal to the average data rate.. QoS profiles on AireOS WLC use a token bucket model where the burst data rate sets the maximum instantaneous rate and must be at or above the average rate for traffic to pass.
Question
An engineer configures QoS on an AireOS WLC v8.5. The engineer configures a WLAN for voice traffic and must set the data rates within the QoS profile. How should the data rates be configured to ensure that the QoS profile allows traffic to and from the wireless client?
Options
- AThe burst data rate should be configured before the average data rate.
- BThe burst data rate should be greater than or equal to the average data rate.
- CData rates should be applied per AP radio.
- DThe burst data rate should be set to a non-zero value.
How the community answered
(27 responses)- A4% (1)
- B81% (22)
- C11% (3)
- D4% (1)
Why each option
QoS profiles on AireOS WLC use a token bucket model where the burst data rate sets the maximum instantaneous rate and must be at or above the average rate for traffic to pass.
The sequence in which burst and average data rates are entered does not affect policy enforcement - both values are evaluated together at commit time, not in entry order.
In AireOS WLC QoS profiles, the burst data rate defines the maximum short-term throughput allowed, while the average data rate defines the sustained rate. If the burst rate is set lower than the average rate, the WLC considers the policy invalid and will block traffic to and from the client, so burst must be greater than or equal to average to permit any traffic flow.
Data rate parameters in a QoS profile are applied per WLAN profile, not per AP radio; per-radio data rate settings are a separate configuration found under the AP or RF profile, not the QoS profile.
Setting the burst rate to a non-zero value alone is necessary but not sufficient - if the non-zero burst rate is still less than the average data rate, the policy is invalid and traffic will not be passed.
Concept tested: AireOS WLC QoS profile token bucket rate configuration
Source: https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/config-guide/b_cg85/qos.html
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