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How the Access Point distinguishe the client's CW??

Level 1
Level 1

Hi all

according to the figur i attached, we know that when a wireless client want to send traffic to the AP (in upstream direction), this client must select back-off time between 0 and CWmin. the Client's CWmin is given by the AP via the beacon frame.

Now if we have 3 clients as shown in the figure, and they want to send different traffic, how AP distinguishe which station want to send voice, which station want to send data and which station want to send video.??? on another meaning, does the AP give all clients the same CWmin in order for them to transmit traffic to the AP???

Please help

Thank you

6 Replies 6

Level 5
Level 5

During the initial client association, the AP and client will negotiate on the QoS and this value will be stored against the client in the controller data base. Hence when a cleint want to send the traffic, the controller/AP will have the information on what type of QoS is associated with the client

Thank you for the reply.

your saying is sensable but now i'm confused.  you said the CW will be stored in the AP's data base after the

negotiation process, which data base do you mean? do you mean the Access Categories as shown in the figure i attached or somewhere else ?

Tank you very much.


The below is from the cleint details in the WLC, i dont have an Autonmous AP which I can access, hence i m not sure wher you can find the this infromation . But if somewher you can get the details of the client, you will find this infromation

sorry i did not understand, do you mean this is all done (CW negotiation process) when the QoS is disabled at the AP?

Thank you


When the QoS is disabled on the AP, all the clients will default to Best Effort QoS, there wont be any negotiation

Amjad Abdullah
VIP Alumni
VIP Alumni


You can not have different type of services on same WLAN. Each WLAN will have it's own services.

There should be one WLAN for data, one separate WLAN for voice and a third one for Video.

When a client tries to connect to data WLAN it uses data CW timers. the same for the others.

Clients connected to same WLAN can not use different CW timers. They will always use same timers if they are connected to same WLAN.

This is why you need to separate different services under different WLANs.

Hope this is helping.


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