300-425 · Question #75
Which option is an enhancement of enabling WMM on an AP?
The correct answer is C. Each access class has its own IEEE 802.11 sequence number. WMM enhances 802.11 QoS by giving each of its four access categories its own independent sequence number counter, enabling per-class traffic management and retransmission tracking.
Question
Which option is an enhancement of enabling WMM on an AP?
Options
- AAll access classes use the same IEEE 802.11 sequence number.
- BIt disables U-APSD Power Save.
- CEach access class has its own IEEE 802.11 sequence number.
- DCAC is reserved for voice calls only.
How the community answered
(59 responses)- A2% (1)
- B5% (3)
- C92% (54)
- D2% (1)
Why each option
WMM enhances 802.11 QoS by giving each of its four access categories its own independent sequence number counter, enabling per-class traffic management and retransmission tracking.
Sharing a single sequence number across all access classes is the pre-WMM behavior; WMM does the opposite by separating sequence numbering per access class.
WMM enables and depends on U-APSD (Unscheduled Automatic Power Save Delivery) for power-efficient delivery of prioritized traffic - it does not disable it.
WMM (based on 802.11e) defines four access classes - Voice, Video, Best Effort, and Background - each operating as a logically independent transmit queue with its own IEEE 802.11 sequence number space, which allows the receiver to track and reorder frames per class independently rather than across all traffic.
CAC under WMM can be applied to both voice and video access classes, not exclusively to voice calls.
Concept tested: WMM per-access-class IEEE 802.11 sequence numbering
Source: https://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/68332-wme-understand.html
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