Windows, DSCP Tag, Do you set manual port range ?

Hello ​@JHS_Durham 

For good or bad, I think you need to be looking at the Windows settings and not the Zoom settings, which by default comes preconfigured with an industry standard QoS settings.

Let me start by saying that you are correct thinking that Windows settings adjust DSCP to 0 by default so it is very possible it is overriding whatever you might be settings in Zoom (or any other Windows App for that matter) so that is what you need to look first.

For the QoS to actually works, the App needs to mark it (optional if you set your OS to do it on behalf of the App), but also, the Switch and the Router used in your network needs not only to keep it, but also to “honor” those markings when it comes to prioritize the traffic. Ultimately, Internet all the prioritization ends  at your Edge Internet Router because as far as I know, Internet doesn't honor QoS markings unless you have to special agreement with a WAN provider.

According to Microsoft documentation, there are 3 paths for the Windows DSCP configuration but all of them lead you to the same mechanism in the backend Windows QoS engine:

1. Group Policy (Assuming you are in an Enterprise Managed Computers)
2. Intune Settings/Endpoint Security, which is more or less a cloud version of the Option 1
3. PowerShell, Local Computer configuration

If you already have Option 1 or 2 implemented, that is the path you need to follow; if your computer(s) are not centrally managed I guess you can configure them individually using the option 3.

The important part if that you have to manually configure the policies and select/mark the Apps because Windows will not do it automatically if I understand the documentation correctly.

You might need to do some testing and verify as I am not expert on the Windows side (or ask something well-versed in Windows and Windows Networking) but it should look something like:

1⃣ Policy 1: Zoom main client (Zoom.exe)

New-NetQosPolicy
  -Name "Zoom-App-DSCP-AF41"
  -AppPathNameMatchCondition "*\Zoom\bin\Zoom.exe"
  -DSCPAction 34
  -NetworkProfile All

2⃣ Policy 2: Zoom media / screen sharing (CptHost.exe)
!--scriptorstartfragment-->

New-NetQosPolicy
  -Name "Zoom-Media-DSCP-AF41"
  -AppPathNameMatchCondition "*\Zoom\bin\CptHost.exe"
  -DSCPAction 34
  -NetworkProfile All

!--scriptorendfragment-->

3⃣ Optional: Voice‑priority model (if your network is voice‑optimized, it needs to match its settings)

New-NetQosPolicy
  -Name "Zoom-Voice-EF" 
  -AppPathNameMatchCondition "*\Zoom\bin\Zoom.exe"
  -DSCPAction 46
  -NetworkProfile All

You can verify the policies applied:

Get-NetQosPolicy | Select Name, AppPathNameMatchCondition, DSCPAction

In Wireshark you should see (assuming all is right) DSCP 34 (AF41) or 46 (EF):

• Inspect IP header 
  • IPv4: DSCP field
  • IPv6: Traffic Class

If you need to clean up the policies:

Remove-NetQosPolicy -Name "Zoom-App-DSCP-AF41"
Remove-NetQosPolicy -Name "Zoom-Media-DSCP-AF41"

Let us know if this works for you.

​@Vinnie