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Aruba instant Wifi multimedia best practices and DSCP mappings

  • 1.  Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 15, 2020 05:10 AM
    Hi All,

    So i like to optimize the WiFi multimedia settings with a correct DSCP mapping. 

    Now im really confused. If i look at cisco deployments, a DSCP mapping for voice is set to 46. Now for Aruba, i can see in the documentation that it uses 48/56. (WMM Traffic Management (arubanetworks.com))

    Can anyone explain to me why this is different between vendors? Should it not be the same?

    Second, im wondering what share % and DSCP settings you use in your deployment and why.

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    James -
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  • 2.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 16, 2020 03:39 PM
    If this is the wrong section for this topic, please let me know or move it please.

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    James -
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  • 3.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 16, 2020 08:33 PM

    the key thing is that the WMM marking should match your LAN switch CoS/DSCP



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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba.
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  • 4.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 20, 2020 07:52 PM

    Hi James,

    In the first place WMM must be supported by the endpoint application. The WMM information from the application (MS Teams for example) will be add WMM information in the 802.11 frames that are send to the access point. When reached at the access point the AP will "translate" the WWM queues into a DHCP value that's add to the ethernet interface of your AP. The DHCP value must be end-to-end deployed on your wired infrastructure.

    WMM have four queues; (AC): voice (AC_VO), video (AC_VI), best effort (AC_BE), and background (AC_BK) that can be mapped to a DSCP value. When leaving blank the defaults would be used, but you can change it to allign with your wired infrastructure.


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    Marcel Koedijk | MVP Expert 2020 | ACMP | ACCP | Ekahau ECSE
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  • 5.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 21, 2020 07:19 AM

    Hi Marcel,

    Just to confirm:

    •  The DSCP mapping works for upstream and downstream traffic.
    • -On the LAN COS 5 = EF46 = Voice                              (DSCP 48 / COS 6 is reserverd by network control services and we dont want to use this here)

    So we want the IAP/controller to egress the traffic with EF46, so we can just honor it on the LAN and put it in the voice queue

    • On the WLAN WMM6 = DSCP48 = Voice
    • On the WLAN WMM5 = DSCP46 = Video
    • On the LAN WMM6 = DSCP48 = Reserved
    • On the LAN WMM5 = DSCP46 = Voice

    Scenario 1 with default settings:

    So for upstream traffic, the client sends a UP5 - DSCP of 46, it will be put in the video queue instead of the voice queue.

    Also for downstream traffic, we want the EF46 from the LAN to be in the voice queue as well.

    So if i want the LAN and WLAN to be matched, i think i need to do a remapping of DSCP46 to Voice queue is this correct?

    Then scenario 2 with default settings:

    The client sends WMM up value of 6. The controller maps this to DSCP 48 but we dont want this to egress in the LAN, because DSCP48 is reserverd.

    So when i set the DSCP mapping for voice to 46,  does the traffic gets remarked to DSCP46 as well?



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    James -
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  • 6.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 21, 2020 09:47 AM

    When the WMM standard was defined, they used the 802.1p COS model to define the eight WMM queues. The Voice over IP (VoIP) community established a standard DSCP value for voice traffic, Expedited Forwarding-46 (EF-46). This strictly maps DSCP to WMM queuing resulting in EF-46 traffic being marked as WMM-VI. Inappropriate classification of upstream EF-46 traffic to WMM VI is a side effect of the general purpose operating system on which SfB runs. Client devices and APs that run on purpose built operating systems are not classified inappropriately, since the manufacturer sets the mappings correctly. Aruba recommends the workaround address upstream mistagging by applying higher DSCP values to wireless clients instead.

    AFAIK mapping is in both directions.



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    Marcel Koedijk | MVP Expert 2020 | ACMP | ACCP | Ekahau ECSE
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  • 7.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 21, 2020 11:10 AM

    Hi, I'm not sure I understand this correctly. So you say that the client should send a higher dscp value than EF46?

    So what about the egress traffic that is send to the Lan? Can you give an example like my 2 scenarios?

    So do you leave the dscp mapping default normally? Or set voice to dscp46? 



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    James -
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  • 8.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 21, 2020 02:40 PM

    Hi James,

    Have to say i have no much practical experience with WMM, more theoretical so you have to validate my answer. Please don't tell anybody ;). AFAIK the WMM Mapping works in both directions. Because you like your downstream traffic from DCHP 46 to WMM voice, i think you have to modify the default mapping and put WMM Voice to value 46.

    For upstreamtraffic when a client application send WWM AC_VO6, it will map AC_VO to DHCP 46.

    You could verify your setup by wireshrak to check if all DSCP values are handled correctly. 

    All Aruba Accesspoint are WMM certified, you have to be sure your client device and client application are also WMM certified to let it work.

    Hope somebody will correct me, if i make a mistake on this ;).

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    Marcel Koedijk | MVP Expert 2020 | ACMP | ACCP | Ekahau ECSE
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  • 9.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 21, 2020 03:16 PM

    Thank you for taking the effort to answer in this topic. .. I'll setup a lab and do some testing. I'll share it on this forum. 



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    James -
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  • 10.  RE: Aruba instant Wifi multimedia best practices and DSCP mappings

    Posted Dec 28, 2020 04:22 AM

    So i did some testing in my lab with 8.5. I only share the interesting finds:

    So when i configure a client with DSCP 46, and the WMM settings are default on the iap, i can see that this will be put in the voice queue. I used show ap debug client-stats and can see the Rx WMM [VO] increase. 

    This was not what i expected but im glad it is put in the voice queue.

    Second, i configured the DSCP  or the client with 48. Again this is in de voice queue and also on the wired site it comes out of the IAP as DSCP48.

    When i change the WMM settings voice to 46 in the IAP, i can see remapping happens and that  on the wired site it comes out of the IAP as DSCP46.

    So to answer my own question... as long the clients are configured with DSCP46, you dont need to ajust the settings. If clients DSCP are higher, you want to remap it to the lower value so it will be in correct cueue on the LAN side. 



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    James -
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