Cisco Cisco Aironet 3700i Access Point Weißbuch

 

 

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The next step is to apply the newly created Air Time Fairness policy to: all access points; a select group of access 

points; or to an single access point in a given WLAN (SSID). This step effectively assigns an SSID to a time slice. It 

is worthwhile to note that multiple SSIDs can be assigned to the same time slice. 

However, this generally assumes a single customer requires multiple SSIDs for some business-related reason. 

Furthermore, an access point can support multiple WLANs with multiple policies. Policies set in individual access 

point and access point group configurations always override per-global network policies. 

All traffic from a given SSID utilizes the assigned time slice for transmissions. Downlink traffic destined for different 

SSIDs will share the same time slice, and will share it in a first-come-first-served manner. 

Next, consider a potential scenario that uses this mechanism (Figure 3). Assume a public Wi-Fi venue exists, 

where the venue WLAN provides services for itself and also for two service providers who lease the WLAN. 

The network administrator assigns Time Slice 1 to the venue owner and assigns 10 percent of the available airtime 

to Time Slice 1. SSID 1 uses Time Slice 1 for the venue owner. 

Next, the network administrator assigns Time Slice 2 to Service Provider A and assigns 45 percent of the available 

airtime to Time Slice 2. Note that Time Slice 2 could support two different networks (SSIDs) for Service Provider A. 

In this example, the SSIDs A_Network_1 and A_Network_2 both share Time Slice 2 since Service Provider A is 

leasing 45 percent of the available airtime. 

Finally, the network administrator assigns Time Slice 3 to Service Provider B and assigns 45 percent of the 

available airtime to Time Slice 3. Time Slice 3 could also support two different networks (SSIDs) for Service 

Provider B. In this example, the SSIDs B_Network_1 and B_Network_2 both share Time Slice 3 since Service 

Provider B is leasing 45 percent of the available airtime. 

Figure 3.    SSID Example 

 

What the Air Time Fairness Solution Is Not 

Before explaining Air Time Fairness in further detail, note that the solution does not replace Enhanced Distributed 

Channel Access (EDCA). Instead, it is applied in conjunction with EDCA. In the downlink direction, the queues that 

feed the EDCA output buffers are serviced in such a way to permit airtime to be distributed or allocated unequally 

per group. The queues are based on the types of users, devices, etc., instead of allowing only traffic patterns to 

determine medium access time.