The Windows Operating System reserves 20% of the total Internet bandwidth for the QOS or Quality of Service usage like Windows update, license renewal, etc. Thus, when you limit the Reservable Bandwidth of the operating system to 0,
this will definitely affect the operating system activities like Automatic Windows Updates.
If a QoS-aware application reserves more bandwidth than it uses, then the unused, reserved bandwidth is available for use by other applications. The reservation does not ensure that the bandwidth will be available to the QoS-aware application
because applications that are not QoS-aware might consume too much bandwidth.
For more information, you may refer to the TechNet article: “QoS Tools and Settings” from this link: