Cisco Cisco AP541N Wireless Access Point Maintenance Manual

Configuring Quality of Service (QoS)

Cisco AP541N Dual-band Single-radio Access Point Quick Start Guide

93

 

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.