non-WMM client, QoS Profiles and CAPWAP DSCP Marking

Johannes Luther · ‎07-16-2010

Hi Board,

I have a QoS question regarding upstream traffic (Client -----> AP -----> Controller) for non-WMM clients.

Here's a quote from the "Wireless Mobility Design Guide" and "Voice over Wireless Design Guide":

"Non-WMM clients have the DSCP of their LWAPP tunnel set to match the default QoS profile for that WLAN. For example, the QoS profile for a WLAN supporting Cisco Unified Wireless IP Phone 7920s would be set to platinum, resulting in a DSCP classification of EF for data frames packets from that AP WLAN."

Referring to the "802.11e/WMM <--> WLAN QoS Profile <--> DSCP" mapping table, the DSCP values of 56, 48 and 46 are mapped to the "Platinum QoS Profile"

So - if a wireless frame (non-WMM) arrives at my Lightweight AP in a "Platinum" SSID, how is the outgoing CAPWAP data packet marked? Is it DSCP 56, 48 or 46?

The same question is for the other classes ("Gold, Silver, Bronze").

Thanks in advance!

Johannes

dperowne · ‎04-04-2012

The WLAN can only re-mark client traffic that has existing DSCP values in the original packet, typically at the application layer. The platinum profile itself has 46 as VoWLAN, 48 as Mgmt traffic (CAPWAP etc), and 56 as network traffic, classifying them as such based on the original marking. The values are only remarked if the configured SSID is different.

This link provides a few more details:

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_configuration_example09186a00807e9717.shtml

jeremy.alexandre.alt · ‎10-07-2016

Hi,

I have the same question:

I have configured a small LAB with a WLC (8.3 software)

Regarding upstream traffic (Client -----> AP -----> Controller----> Server) for non-WMM clients.

I generate a ICMP packet with a DSCP32 from my no WMM client to a server.

My QoS profil is Platinum.

I checked the outgoing CAPWAP header packet and it's marked at DSCP 26 (AF31).

Why this behavior ? As my understanding, the CAPWAP header should be marked DSCP 46 (EF), No ?

Thanks for your help.

Rgds.

Rasika Nayanajith · ‎10-10-2016

Hi

Prior to 8.0 software releases UP value will be used to derive the CAPWAP header DSCP values.

In later release, original packet DSCP value is used to derive CAPWAP header DSCP (no longer UP value used)

HTH

Rasika

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jeremy.alexandre.alt · ‎10-11-2016

Hi Rasika and thx for your help.

I understand but in this case, why I have DSCP 26 instead of 32 on CAPWAP header ? (Remember that I look only the upstream for non WMM client in this example ; There are no UP field on 802.11).

Furthemore, I have a WLC default QoS config (I don't check the "Trust DSCP UpStream" checkbox on QoS config.

Tkanks :)

dperowne · ‎11-16-2016

Most vendors have only implemented a subset of 802.11e, being WMM, meaning you need support from both the AP and the client to use it to maximum effect.

The reason people use WMM compatible devices if they want to implement QoS is because packets need to be marked by the client prior to being sent to the AP because they only copy the markings to the header if they already exist, they don't remark them.

At what point are you checking the packet? Over the air, on the laptop or LAN? What is your switch configuration between the AP and the WLC? If you don't trust DSCP at that point, it can remark to a different value, normally best effort if everything is default. You also have to check the WLC ports connected to the network for traffic egress (port/vlans) and see what is set.

What is happening in your case is either the client is sending it as what you see, or it's potentially getting remarked at the AP port ingress to LAN or the WLC egress/LAN port ingress. No matter what happens, you won't see 46 unless you are originating that from the client or specifically remarking it on the LAN somewhere.