Cisco Small Business AP541N Administration Manual page 98

Wireless
Configuring Quality of Service (QoS)
Cisco AP541N Dual-band Single-radio Access Point Quick Start Guide
Table 24 QoS Parameters (Continued)
Field
AIFS
(Inter-Frame Space)
cwMin
(Minimum
Contention Window)
cwMax
(Maximum
Contention Window)
Description
The Arbitration Inter-Frame Spacing (AIFS) specifies a
wait time for data frames. The wait time is measured in
slots. Valid values for AIFS are 1 through 255.
This parameter is input to the algorithm that determines the
initial random backoff wait time (window) for retry of a
transmission.
The value specified for Minimum Contention Window is the
upper limit (in milliseconds) of a range from which the initial
random backoff wait time is determined.
The first random number generated will be a number
between 0 and the number specified here.
If the first random backoff wait time expires before the data
frame is sent, a retry counter is incremented and the
random backoff value (window) is doubled. Doubling will
continue until the size of the random backoff value reaches
the number defined in the Maximum Contention Window.
Valid values for cwMin are 1, 3, 7, 15, 31, 63, 127, 255, 511, or
1023. The value for cwMin must be less than or equal to the
value for cwMax.
The value specified for the Maximum Contention Window is
the upper limit (in milliseconds) for the doubling of the
random backoff value. This doubling continues until either
the data frame is sent or the Maximum Contention Window
size is reached.
Once the Maximum Contention Window size is reached,
retries will continue until a maximum number of retries
allowed is reached.
Valid values for cwMax are 1, 3, 7, 15, 31, 63, 127, 255, 511,
or 1023. The value for cwMax must be higher than or equal
to the value for cwMin.
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