Define the steps on how to configure DSCP / QoS on Linux and Mac endpoint running RTME to complement:

Citrix Documentation - Technical overview: Supports Differentiated Services Code Point (DSCP) marking for media packets. For Windows, push out QoS GPO policies to the endpoints. For Linux and Mac OS X, there are RealTime Optimization Pack registry settings that must be applied in the user's profile on the server.

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Instructions

Caution! Refer to the Disclaimer at the end of this article before using Registry Editor.

1. On the VDA, locate or create a registry key HKEY_CURRENT_USER\Software\Citrix\HDXRTConnector\MediaEngine\Networking      

2. Under this key, create three DWORD values: AudioTOS, VideoTOS, RtcpTOS. Set them to the desired value of the IP TOS byte.

3. Restart Skype For Business.

4. Note that registry settings control the full TOS byte, so if you want to use a particular DSCP value, multiply it by 4.

5. RtcpTOS is applied to RTCP packets for both audio and video, the other values are applied to RTP packets for audio and video, respectively.

6. The settings are only applied on Linux and OSX endpoints. For Windows endpoints, these settings will be ignored. QoS for Windows endpoints needs to be configured using the Group Policy-based QoS mechanism with policies applied at the endpoint.
   
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   Remember, for non-windows devices you need to multiple your desired DSCP value by 4 and set this new value via the registry.
   
   Here is an example:
   
   [HKEY_CURRENT_USER\Software\Citrix\HDXRTConnector\MediaEngine\Networking]
   "AudioTOS"=dword:000000b8
   "VideoTOS"=dword:000000a4
   "RtcpTOS"=dword:00000080
   
   Hex(b8) = Dec(184) -> DSCP = 184 / 4 = 46 is the actual DSCP value you want to see in the network traffic
   Hex(a4) = Dec(164) -> DSCP = 164 / 4 = 41 is the actual DSCP value you want to see in the network traffic
   Hex(80) = Dec(128) -> DSCP = 128 / 4 = 32 is the actual DSCP value you want to see in the network traffic
   
   
   The reason for the Multiply by 4 appears to be to requirement to meet the full ToS specification – which has two bits at the end for ”ECN” (see the Wikipedia article for more details) – 00 just means these are not configured, and this then bit-shifts the same DSCP value over first 6 bits, like this:
   the ecn, last two bits, is always 00. 
   
   
   By Multiplying by 4 you basically do a bit shift:
   46 in binary is 101110
   But you have to set 8 bits (in order to comply with the RFC), so basically add 00 at the end (or multiple by 4): 184 in binary is 10111000
    

Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

The Optimization Pack supports DSCP marking for media packets. The HDX RealTime Media Engine is functionally equivalent to the Skype for Business media stack. For Windows, push out QoS policies to the endpoints. For Linux and Mac OS X, there are RealTime Optimization Pack registry settings that must be applied in the user’s profile on the server. For GPO-based QoS packet tagging, verify that: - the GPO is applied on Windows devices running HDX RTME (applying the GPO on the VDA side would not have any effect) - that the GPO defines DSCP values for audio and video port ranges defined on the Skype for Business Server using the Set-CsConferencingConfiguation cmdlet (https://technet.microsoft.com/en-us/library/gg412969.aspx) HDX RT Optimization Pack 2.x obeys the AudioPort/VideoPort and range settings (it ignores the MediaPort setting). The GPO needs to be defined accordingly.

https://www.citrix.com/blogs/2017/12/19/rtop-dont-forget-about-qosdscp/