Configure DSCP Marking for Executables via Regedit

This guide explains how to configure Differentiated Services Code Point (DSCP) packet marking for specific application executables using the Windows Registry Editor (regedit). Implementing DSCP values allows network equipment, such as managed switches and routers, to prioritize or classify network traffic generated by critical software on your Windows system.

Step 1: Enable TCP/IP DSCP Support

Before defining per-application QoS policies, you must ensure the Windows TCP/IP stack allows user-defined DSCP/TOS markings.

Press Win + R, type regedit, and press Enter.

Navigate to the following path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Check for a DWORD (32-bit) value named DisableUserTOSSetting.
- If it does not exist, right-click the Parameters folder, select New > DWORD (32-bit) Value, and name it DisableUserTOSSetting.
Double-click DisableUserTOSSetting and set its value to 0 (Base: Hexadecimal or Decimal).

Step 2: Create the QoS Registry Policy

Quality of Service (QoS) rules can be injected directly into the Windows Policy registry structure.

In the Registry Editor, navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows

Check if a key named QoS exists under Windows. If not, right-click the Windows key, select New > Key, and name it QoS.
Right-click the QoS key, select New > Key, and give it a descriptive name for your application (e.g., MyCustomApp).

Step 3: Configure the Application Traffic Rules

Inside your newly created application subkey (e.g., HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\QoS\MyCustomApp), create the following string values (New > String Value):

Value Name	Value Type	Recommended Data	Description
`Version`	String (REG_SZ)	`1.0`	Required schema version.
`Application Name`	String (REG_SZ)	`appname.exe`	The exact name of your executable.
`DSCP Value`	String (REG_SZ)	`46`	The decimal DSCP value (e.g., `46` for Expedited Forwarding).
`Protocol`	String (REG_SZ)	`*`	Specify `*` for all, `TCP`, or `UDP`.
`Local Port`	String (REG_SZ)	`*`	Source port (use `*` for any).
`Local IP`	String (REG_SZ)	`*`	Source IP (use `*` for any).
`Local IP Prefix Length`	String (REG_SZ)	`*`	Subnet prefix length (use `*` for any).
`Remote Port`	String (REG_SZ)	`*`	Destination port (use `*` for any).
`Remote IP`	String (REG_SZ)	`*`	Destination IP (use `*` for any).
`Remote IP Prefix Length`	String (REG_SZ)	`*`	Destination subnet prefix (use `*` for any).

Step 4: Apply the Changes

Registry-based QoS changes require the network stack or system to refresh before packets are marked:

Close the Registry Editor.
Restart your computer, or restart the target network adapter via PowerShell (Run as Administrator):
```
Restart-NetAdapter -Name "YourAdapterName"
```
Use a packet analyzer such as Wireshark to verify that outbound IP packets from the specified executable contain your defined DSCP value in the Differentiated Services Field.