Configures 802.11e/Wireless Multimedia (WMM) parameters for this WLAN QoS policy
WMM makes it possible for both home networks and Enterprises to decide which data streams are most important and assign them a higher traffic priority.
WMM‘s prioritization capabilities are based on the four access categories (background, best-effort, video, and voice). Higher the Access Category (AC) higher is the transmission probability over the controller managed WLAN. ACs correspond to the 802.1d priorities, facilitating interoperability with QoS policy management mechanisms. WMM enabled controllers coexist with legacy devices (not WMM-enabled).
Packets not assigned to a specific access category are categorized as best effort by default. Applications assign each data packet to a given access category. Categorized packets are added to one of four independent transmit queues (one per access category). The client has an internal collision resolution mechanism to address collision among different queues, which selects the frames with the highest priority to transmit.
The same mechanism deals with external collision, to determine which client should be granted the Opportunity to Transmit (TXOP). The collision resolution algorithm responsible for traffic prioritization is probabilistic and depends on two timing parameters that vary for each access category. These parameters are:
The minimum interframe space, or Arbitrary Inter-Frame Space Number (AIFSN)
The contention window, sometimes referred to as the random back off wait
Both values are smaller for high-priority traffic. The value of the contention window varies through time. Initially the contention window is set to a value that depends on the AC. As frames with the highest AC tend to have the lowest back off values, they are more likely to get a TXOP.
After each collision the contention window is doubled until a maximum value (also dependent on the AC) is reached. After successful transmission, the contention window is reset to its initial, AC dependant value. The AC with the lowest back off value gets the TXOP.
wmm [background|best-effort|power-save|qbss-load-element|video|voice]
wmm [power-save|qbss-load-element]
wmm [background|best-effort|video|voice] [aifsn <2-15>|cw-max <0-15>| cw-min <0-15>|txop-limit <0-65535>]
wmm [power-save|qbss-load-element]
|
wmm |
Configures 802.11e/wireless multimedia parameters |
|
power-save |
Enables support for the WMM-Powersave mechanism. This mechanism, also known as Unscheduled Automatic Power Save Delivery (U-APSD), is specifically designed for WMM voice devices. |
|
qbss-load-element |
Enables support for the QOS Basic Service Set (QBSS) load information element in beacons and probe response packets advertised by access packets. This feature is enabled by default. |
wmm [background|best-effort|video|voice] [aifsn <2-15>|cw-max <0-15>| cw-min <0-15>|txop-limit <0-65535>]
|
wmm |
Configures 802.11e/wireless multimedia parameters. This parameter enables the configuration of four access categories. Applications assign each data packet to one of these four access categories and queues them for transmission. |
|
background |
Configures background access category parameters |
|
best-effort |
Configures best effort access category parameters. Packets not assigned to any particular access category are categorized by default as having best effort priority |
|
video |
Configures video access category parameters |
|
voice |
Configures voice access category parameters |
|
aifsn <2-15> |
Configures Arbitrary Inter-Frame Space Number (AIFSN) from 2 - 15. AIFSN is the wait time between data frames. This parameter is common to background, best effort, video and voice. The default for traffic voice categories is 2 The default for traffic video categories is 2 The default for traffic best effort (normal) categories is 3 The default for traffic background (low) categories is 7
|
|
cw-max <0-15> |
Configures the maximum contention window. Wireless clients pick a number between 0 and the minimum contention window to wait before retransmission. Wireless clients then double their wait time on a collision, until it reaches the maximum contention window. This parameter is common to background, best effort, video and voice. The default for traffic voice categories is 3 The default for traffic video categories is 4 The default for traffic best effort (normal) categories 10 The default for traffic background (low) categories is 10
|
|
cw-min <0-15> |
Configures the minimum contention window. Wireless clients pick a number between 0 and the min contention window to wait before retransmission. Wireless clients then double their wait time on a collision, until it reaches the maximum contention window. This parameter is common to background, best effort, video and voice. The default for traffic voice categories is 2 The default for traffic video categories is 3 The default for traffic best effort (normal) categories is 4 The default for traffic background (low) categories is 4
|
|
txop-limit <0-65535> |
Configures the transmit-opportunity (the interval of time during which a particular client has the right to initiate transmissions). This parameter is common to background, best effort, video and voice. The default for traffic voice categories is 47 The default for traffic video categories is 94 The default for traffic best effort (normal) categories is 0 The default for traffic background (low) categories is 0
|
nx9500-6C8809(config-wlan-qos-test)#wmm video txop-limit 9
nx9500-6C8809(config-wlan-qos-test)#wmm voice cw-min 6
nx9500-6C8809(config-wlan-qos-test)#show context wlan-qos-policy test classification non-wmm video svp-prioritization voice-prioritization wmm video txop-limit 9 wmm voice cw-min 6 multicast-mask primary 11-22-33-44-55-66/22-33-44-55-66-77 classification non-unicast normal rate-limit wlan from-air rate 55 rate-limit wlan from-air max-burst-size 6 rate-limit wlan from-air red-threshold best-effort 10 rate-limit client from-air red-threshold background 3 qos trust dscp qos trust wmm accelerated-multicast autodetect classification voice nx9500-6C8809(config-wlan-qos-test)#