WMM Wireless QoS over Cisco

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Jun 14th, 2010
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I have a customer that have none cisco softphones installed on thier laptops. In the softphone application we set the DSCP to use for RTP traffic to 46 to comply with Cisco medianet. This works well as long as the client is wired. Problem comes with wireless.

WMM and 802.11e states that class 6 and 7 is voice. WMM maps DSCP 48 to class 6 and 56 to class 7 both these classes end up in AC_VO. DSCP 46 on the other hand maps into class 5 witch maps into AC_VI (Video).

The result is that all traffic from the softphone client is treated as video over the wireless and exiting the AP on the wire the traffic is marked with DSCP 34.


I can handle remapping DSCP 34 to DSCP 46 (EF) after the WLC but the question is: Do the APs treat the traffic correctly over the air?

I have tried to find a way to modify the settings in the clients wireless nic so that DSCP 46 maps to WMM class 6 but no go. I have also tried to find any specs on the differences in trestment of  AC_VI and AC_VO in Cisco Lightweight AP to see if it's accceptale but info is very sparse.


Anyone got any ideas how to deal with this beside just changing the softphone settings to send traffic with dscp 48?


Some hard facts:

Clients: Stationary PC with EDIMAX EW7228In or Laptops with various Intel nics

Network: Cisco 5508 WLC running 6.0.196.0 and AP1142n accespoints.

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volven.didata Tue, 08/31/2010 - 21:10
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Hi There,


I'd be interested to know if you got any answer to your querry? I am currently looking at something similar and would like to know from you on how you got around applying QoS for the softphones operating on Data WLAN.


Thanks


Volven

sokarlsson Wed, 09/01/2010 - 04:35
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Volven so far I have only recieved an answer from TAC that Ciscos equipment works by design. I have also tested and analyzed the traffic and come to the conclusion that the software on the WMM enabled client must mark the traffic with DSCP 48 for it to be properly marked as voice over the air.
I suppose that the only thing to do is to buy the situation and handle the DSCP 48 to EF mapping on the switchports that the laptops connect to when wired. This will of course require that the switchmodels and IOS used support class and policy maps.
I'm still waiting for a suggestion from Cisco on how they think one should solve this.


Stefan

volven.didata Wed, 09/01/2010 - 04:55
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Hi Stefan, thanks for sharing the info. I'll let you know what path we end up taking...


Cheers


Volven

Steven DiStefano Wed, 09/01/2010 - 06:06
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Hi Guys,

If this is UC500 Wifi related, I wanted to share what I know here.  This happened back in CCA 1.9 time frame.  Is this what you are looking for?




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WMM (WiFi Multi Media) allow Diff-serv QoS by creating 4 priority queues, called Access Categories based on 8021d COS.


802.1d COS            802.11e(WMM)

0,3                            1 best effort

1,2                            0 back ground

4,5                            2 video

6,7                            3 voice


So mapping DSCP to COS is done in UC500:


class-map match-all _class_Voice0

match ip dscp ef

class-map match-all _class_Voice1

match ip dscp cs3

!       

policy-map Voice

class _class_Voice0

  set cos 6

class _class_Voice1

  set cos 3


Then on the Radio interface the Policy is assigned:

interface Dot11Radio0/5/0

no ip address

!      

ssid office-data

!      

ssid office-voice

!      

speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 12.0 18.0 24.0 36.0 48.0 54.0

station-role root

antenna receive right

antenna transmit right

!      

service-policy output Voice

sokarlsson Fri, 10/01/2010 - 07:46
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Appreciate your efforts Steven but at least my problem is on the client (PC,softphone,WMM enabled nic) side where WMM screw everything up.
The softphone mark with DSCP EF and since WMM is then hardcoded to remap to AC_VI thus RTP from the client is treated as video traffic.

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