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In which field does beacon frame contain WMM parameters?

Level 1
Level 1

Hi all,

can you please help me on this as I could not find enough information.

when the access point transmits the CWmin/max parameters to the wireless client, it sends them via the bacon frame.

now the question is:

when does the AP send these parameters? (is it when we turn on the AP  or  when we apply QoS at the AP?)

Can anyone provide me an evidance (material) that explains WMM section in the beacon frame?

Please help me, I could not understand this.

Thank you


8 Replies 8

Level 5
Level 5


  Element ID:           221  WMM

  Length:               24

  OUI:                  0x00-0x50-0xF2

  OUI Type:             2

  OUI SubType:          Parameter Element

  Version:              1

  QoS Info:             %10000000

                        1... .... WMM AP supports U-APSD

                        .xxx .... Reserved

                        .... 0000 Parameter Set Count: 0

  Reserved:             0x00

  Access Category - Best Effort

  ACI/AIFSN:            %00000101

                        x... .... Reserved

                        .00. .... ACI: Best Effort

                        ...0 .... ACM: Admission Control Not Mandatory

                        .... 0101 AIFSN: 5

  ECW Min/Max:          %10100110

                        1010 .... ECW Max: 10 (CW Max: 1,023)

                        .... 0110 ECW Min: 6 (CW Min: 63)


this is very important information. Can you please tell me where can i find this information? i mean i need a reference which explains which you said, if this information is explained in cisco website please send me the link. I need this because I will include it in my dissertation.

Please help

Thank you

I just checked one of the beacons i had captured.. coudlnt find it the Cisco site

Amjad Abdullah
VIP Alumni
VIP Alumni


There is always default QoS profile added to the WLAN. So CWmin/CWmax will always pick up the values related to the default QoS profile chosen (if you did not change the default).

If you change the default QoS profile however, the CWwin/CWmax will change according to the QoS profile you have chosen.

So whenever there is WLAN those informaiton will be sent in the beacon because there is always a QoS profile chosen.

Hope this clear.

This link describes about QoS over wireless. It shows you that there are 4 different queues, one for each type of QoS. (Platinum, Gold, Server and Bronze).

Your traffic will reside in one of those categories and can not be out of those. So your beacons will always have the information.

in short, there are always QoS profile applied to the WLAN and the whenever there are beacons the information you mentioned will be always there.


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Hi all,

Any one knows if there is any way to customise AIFS, CWmin, CWmax and TXOP parameters?



Enrique, Hi,

I could find no way to manually change the values of the variables you mentioned on cisco wireless controller.

However, I am in version and I think there are like templates to change those variables (but the actual values are not mentioned on the WLC).

From WLC GUI go to Wireless Tab then to: 802.11a/n (or 802.11b/g/n) -> EDCA Parameters.

From there you can change the EDCA profile. Each profile you choose may have different values for AIFS, CWmin, CWmax and/or TXOP.



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Hi Amjad,

Thanks for you quick response. As you've said, EDCA profiles have different values for the parameters I mentioned. But they are fixed values, I would like to change them to my will for testing purpose. I guess I'll have to look for a different platform for these tasks.

Thanks again,


That's what I am saying. You can not change it. you are limited to the template that you choose.

I've seen those values changable with other vendors though. But with Cisco I could not find anywhere to change those except the EDCA profiles.



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