A cabinet (CAB) file is a compressed library containing the payload files needed to enable Windows features. For .NET Framework 3.5, the specific file is typically named microsoft-windows-netfx3-ondemand-package.cab .
Microsoft provides this file within the (ISO or DVD) of the operating system, specifically located in the \sources\sxs folder. Why Use a CAB File for Installation? cab file for .net framework 3.5
The most reliable method to install this package is through the tool. Step 1: Locate the CAB File Install .NET Framework 3.5 on Windows 10 - Microsoft Learn A cabinet (CAB) file is a compressed library