Extreme Networks Altitude 4700 Series Product Reference Manual page 159

Background
Best Effort
Video
Voice
8 Configure the CW min and CW max (contention windows), AIFSN (Arbitrary Inter-Frame Space
Number) and TXOPs Time (opportunity to transmit) for each Access Category. Their values are
explained as follows.
CW Min
CW Max
AIFSN
TXOPs Time
32usec
TXOPs Time ms
9 Click Apply to save any changes to the New QoS Policy or Edit QoS Policy screen to return to the
Quality of Service Configuration screen. Navigating away from the screen without clicking Apply
results in all changes to the screens being lost.
10 Click Cancel to securely exit the New QoS Policy or Edit QoS Policy screen and return to the Quality
of Service Configuration screen.
11 Click Logout within the Quality of Service Configuration screen to securely exit the Access Point
applet. A prompt displays confirming the logout before the applet is closed.
Altitude 4700 Series Access Point Product Reference Guide
Background traffic is typically of a low priority (file
transfers, print jobs ect.). Background traffic typically does
not have strict latency (arrival) and throughput
requirements.
Best Effort traffic includes traffic from legacy devices or
applications lacking QoS capabilities. Best Effort traffic is
negatively impacted by data transfers with long delays as
well as multimedia traffic.
Video traffic includes music streaming and application
traffic requiring priority over all other types of network
traffic.
Voice traffic includes VoIP traffic and typically receives
priority over Background and Best Effort traffic.
The contention window minimum value is the least amount
of time the MU waits before transmitting when there is no
other data traffic on the network. The longer the interval,
the lesser likelihood of collision. This value should be set
to a smaller increment for higher priority traffic. Reduce the
value when traffic on the WLAN is anticipated as being
smaller.
The contention window maximum value is the maximum
amount of time the MU waits before transmitting when
there is no other data traffic on the network. The longer
the interval, the lesser likelihood of collision, but the
greater propensity for longer transmit periods.
The AIFSN is the minimum interframe space between data
packets transmitted for the selected Access Category. This
value should be set to a smaller increment for higher
priority traffic to reduce packet delay time.
The TXOPs Time is the interval the transmitting MU is
assigned for transmitting. The default for Background
traffic is 0. The same TXOPs values should be used for
either the 802.11a/n or 802.11b/g/n radio, there is no
difference.
TXOP times range from 0.2 ms (background priority) to 3
ms (video priority) in a 802.11a/n network, and from 1.2
ms to 6 ms in an 802.11b/g/n network. The TXOP bursting
capability greatly enhances the efficiency for high rate
traffic such as streaming video.
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