Configuring Lync 2013 VDI Plug-in support for QoS

Abstract: This article leads the reader through the process of enabling DSCP marking for Windows access computers that run the Lync 2013 VDI Plug-in to deliver a great audio and video experience on networks where QoS has been deployed.

I have recently joined Microsoft Services working in the Enterprise Communications Centre of Excellence in EMEA, I have worked on a number of Lync 2013 VDI Plug-in deployments and wanted to share some key learnings relating to configuring the Lync 2013 VDI Plug-in to run in a QoS enabled environment.

The first great thing to understand is that the QoS planning and subsequent PowerShell configuration to separate out the media streams that you already have in place to support your Lync 2013 deployment will be honoured by the Lync 2013 VDI Plug-in.

If you are just starting on configuring Lync 2013 support for QOS, the following planning topic may be beneficial: “Managing Quality of Service (QoS)” at

The second great thing to understand is that the method you used to configure the Windows Packet Scheduler to mark Lync media packets for the Lync 2013 client will be reused also with some minor changes.

The key thing to keep in mind is that the Lync 2013 VDI Plug-in is exactly that, a plug-in installed on the local access computer. The Lync 2013 VDI Plug-in runs on the local access computer and pairs with the Lync Desktop Client running on the remote virtual machine through Remote Desktop Client session. Once you have deployed the Lync 2013 VDI Plug-in onto the local access machine, you will not find a lync.exe process but you will find mstsc.exe, the Remote Desktop client when pairing is successfully established.


So let’s assume that you have already configured your Lync 2013 platform so that your media ports used by the clients are as follows and you have agreed the Differentiated Services Code Point (DSCP) marking scheme with the network team (here we have allocated 100 TCP and UDP ports per modality).




App Sharing

40803 to 40903

DSCP Marking 24


49152 to 49252

DSCP Marking 46


57501 to 57601

DSCP Marking 34


We are assuming that your Windows local access computers are domain joined so all that we need to do now is to create a new Group Policy Object to target our local access computers running the Lync VDI Plug-in so we can apply the DSCP marking scheme simply and consistently. This process is defined in “Configuring Quality of Service Policies for Clients Running on Windows 7 or Windows 8” at 

  1. In Group Policy Management, locate the container where the new policy should be created. For example, if all your VDI end points are located in an OU named VDI End Points then the new policy should be linked to the VDI End Points OU.
  2. Right-click the appropriate container and then click create a GPO in this domain, and link it to the VDI End Points OU.
  3. In the New GPO dialog box, type a name for the new Group Policy object in the Name box (for example, Lync VDI DSCP Marking) and then click OK.
  4. Right-click the newly-created policy and then click Edit.
  5. In the Group Policy Management Editor, expand Computer Configuration, expand Policies, expand Windows Settings, right-click Policy-based QoS, and then click Create new policy.
  6. In the Policy-based QoS dialog box, on the opening page, type a name for the new policy (e.g., Lync VDI Audio) in the Name box. Select Specify DSCP Value and set the value to 46. Leave Specify Outbound Throttle Rate unselected, and then click Next. 

  7. On the next page, make sure that Only applications with this executable name is selected, enter mstsc.exe, and then click Next.
    This setting instructs the network to only look at packets coming from the Remote Desktop client that will match our port definition to mark those packets with a DSCP marking of 46.


  8. On the third page, make sure that both Any source IP address and Any destination IP address are selected, and then click Next.
    These two settings ensure that packets will be managed regardless of which computer (IP address) sent those packets and which computer (IP address) will receive those packets.
  9. On page four, select TCP and UDP from the Select the protocol this QoS policy applies to dropdown list.
  10. Under the heading Specify the source port number select From this source port or range. In the accompanying text box, type the port range reserved for audio transmissions. In our example, we you reserved ports 49152 through ports 49252for audio traffic enter the port range using this format: 49152:49252. Click Finish.

 After you have created the QoS policy for Lync VDI audio you should then create policies for App Sharing and Video.


Save the new GPO and ensure you apply it to the target OU, either reboot the local access machines with or run gpupdate /force once the GPO is available.

We are going to look for two confirmation points:

  • GPO successfully applied
  • Packets are being correctly marked

The first thing to check is that your GPO has applied correctly, go to the local access computer, sign in and open up a command prompt (if you are using a locked down thin client you may need to follow the manufacturer’s procedure to sign in as an administrator before you gain access to the command prompt).

Type gpresult /h c:\temp\report.html


Once the report has been created, open it and search for the name of your GPO (Lync VDI DSCP Marking in our example and confirm it has applied correctly).



 The following screen shot shows a Netmon packet capture showing the DSCP marking enabled on an audio packet from the local access machine (



Once you have confirmed all is well, take the opportunity to make yourself a nice cup of tea!

Configuring Port Ranges for Your Microsoft Lync Clients at

Configuring Quality of Service Policies for Clients Running on Windows 7 or Windows 8 at

Installing the Lync 2013 VDI Plug-in at


Comments (20)
  1. Amana Living says:

    Shouldn't that be destination port, rather than source port used in the QoS policy, you define those specific ports on the front end server, and the client connects to those. The client would use random source ports to connect from.

  2. Hi

    In this case we want to ensure that peer to peer audio and video calls as well as conferences are correctly marked so by setting source port in the QoS policy to match that set using Get-CsConferencingConfiguration we ensure that the clients do not connect using random ports so we can mark traffic correctly.

  3. Ari says:

    there is a 'chance' by using source port and mstsc.exe for the QoS GPO that RDP traffic could be wrongly marked.

    #Lync Question 19: Why VDI is more than just about thin clients…/lync-question-19-why-vdi-is-more-than-just-about-thin-clients

  4. Bill Bartolotta says:

    Good info on VDI Plugin issues.  I have many other issues with the deployment of the VDI Plug-in in Citrix XenDesktop 7.  Some minor, some showstoppers.  I realize that MS and Citrix are still working through issues, but there doesn't seem to be much written or communicated about the VDI Plugin, and for us early adopters, that makes us nervous.  Is there a forum somewhere where some of these experiences could be shared and where MS could chime in on future capabilities that are being developed?

    Among the hot issues I have right now:

    -Inability to choose to have the ringer use the endpoint device's on-board audio vs using headsets.

    -Inability to choose the ringtone sound

    -Inability to actively view stats about the call

    -Troubleshooting is difficult as there is no guidance as to what we should be looking at in the UCCAPI logs re: pairing.

  5. Anonymous says:

    Pingback from Configuring Lync 2013 VDI Plug-in support for QoS : Erez Benari's Blog : The Official Microsoft IIS Site

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