Configuring Voice Quality of Service for Skype for Business Online IP Phones

Neeraj Jain, if you want to do QoS end to end, you will need to have Express Route. However, you can use this tag to prioritize voice traffic in your internal network.

QoS on Skype Online would only work with ExpressRoutes, correct?

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KruthikaPonnusamy wrote:

A recent update enables tenant admins to modify the DSCP (Differentiated Services Code Point) value of voice traffic to enable Quality of Service (QoS).

 

How to Configure Voice Quality of Service

The VoiceDiffServTag represents the DSCP value assigned to voice traffic in Skype for Business. To modify this setting, run the Set-CsUCPhoneConfiguration via Remote PowerShell and set it to desired value. It is recommended that voice traffic be marked with a DSCP value of 46.

 

Call to action:

• If you want to set QoS values for voice traffic in your Skype for Business Online deployments, update the DSCP values to your desired value.
• Any questions or comments? Please let us know below or in our community.

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Thomas Binder Did Microsoft change the DSCP value from 46 to 40 for SfB Online ?

Inbound provisioning give me 
<ucDiffServVoice>40</ucDiffServVoice>

and Get-CsUCPhoneConfiguration give the below.

VoiceDiffServTag     : 40

Can you also confirm that DSCP for video is still 34 and can that be altered or verified by any SfB powershell cmdlet?
thanks

/Markus

Markus_Johansson

Are you sure you are executing the cmdlet against Skype Online PowerShell?  The cmdlet is the same for on-premises (if you have it) and if you haven't connected to remote PowerShell correctly (using -AllowClobber), the command would get executed against your on-premises environment instead of the Online environment.

Also, the DSCP value for video is not listed anywhere in the server configuration.  General network-QoS best practices say to use DSCP 34 for video, but if your network requirements dictate otherwise then it is absolutely possible to do so.  Even so, the only place that value exists is in your networking infrastructure (such as class-maps and queue configuration) or group policy on your Windows clients.

rovert506

I see the same in 3 different tenants.

If you can check your tenant then please run
$tenantID = (Get-CsTenant).tenantid

Get-CsUCPhoneConfiguration -Tenant $tenantID

What is your output from VoiceDiffServTag ?

thanks

/Markus

Markus_Johansson - You had previously used the Set-CsUcPhoneConfiguration cmdlet to set the value for those three tenants?

rovert506 no

Markus_Johansson - Ah, ok...there's your missing piece.  You have to actually set the value first.  See the paragraph directly underneath "How to Configure Voice Quality of Service".  Microsoft simply unlocked the ability to set the value but they didn't change their default configuration, which is 40.  Once you set the configuration in those tenants, it will take some time (8 hours or upon sign-in, whichever is first) before your devices receive the updated configuration.

rovert506 Yes true, got that point but why isn't default 46 as that is what everyone will use anyway :) 
And how can one confirm microsoft is actually using DSCP 34 for video as you can't see it anywhere and there is no config for it. I guess running network trace is the only possibility then.

Markus_Johansson - the 40 value default is an old relic...literally from the Lync Server 2010 days....but it's a confusion as a result of the differences in definition between Precedence Level values and Class Selector values.  See Jeff Schertz's blog for a good explanation on this:

http://blog.schertz.name/2011/08/lync-qos-behavior/

Lastly, as I said before, DSCP for video is not specified anywhere in the server/tenant configuration.  It will NOT be marked by default so you will not see anything on your client if you are taking WireShark traces.  You have to manually configure QoS in Active Directory Group Policy (which then gets assigned to computers) or configure class-maps on your network switches to mark the traffic to the desired DSCP value for your video streams.  Only after you have done that will you see any video streams marked with the appropriate DSCP value (assuming your network infrastructure doesn't strip it along the way).