UWN QOS questions

Unanswered Question

Hello all.

I've got two questions related to wireless QOS in a UWN world:


1) A QOS profile is associated with a WLAN. Is it possible to diferentiate traffic within a single WLAN? Can I assign the gold profile to one DSCP value, and the silver profile to another DSCP - all within the same WLAN? If not, how do others differentiate between applications on a mobile device (email vs. softphone)?


2) Is it possible for the LWAPP AP to remap or set incoming DSCP - the classification and marking functions of QOS (aka establish the QOS classification boundry on the radio). If not, I'm concerned about the WLC maintaining potentially invalid DSCP in the LWAPP header on the way to the controller. How do others ensure they aren't oversubscribing a priority queue on a WAN link from an H-REAP AP to a central site controller?


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Unfortunately, I'm almost positive the answer to both questions is NO.


From the document you referenced -

"The controller does not apply its own QoS. The QoS support on the WLC gives the WLC the ability to apply the same priority that is set on the wire (or application). Therefore, the only action a WLC or AP will do is copy the value of the original packet to the outer header of the LWAPP packet."


For question 1, to use different QOS profiles, we must associate clients to different WLANs. The result is that we are limited to device-specific QOS, as opposed to application-specific QOS. If we want VoIP or Video over wireless, the endpoints (e.g. VoIP handsets) must connect to their own SSID. Softphone traffic can't be preferred over other PC traffic.


For question 2, this means we need to be concerned about the LWAPP AP maintaining potentially invalid DSCP in the LWAPP header on the way to the controller (and vice-versa). The problem comes in that this may oversubscribe a priority queue on a WAN link from a remote AP to a central site controller, unless you are policing at L3 ingress (which isn't without problems too). The way around this is to conditionally clear DSCP on ingress (e.g. not trusting the controller or AP uplink).

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