Devices with serial numbers are enumerated faster, if the same device has been connected to the system on a different port before. When the user plugs in a device without a serial number to a new USB port, the device is set up as if it has never been seen before (a process that may take several seconds). Serial numbers improve the user experience with any USB device in general with Windows, because they allow Windows to keep track of devices no matter what USB port they are plugged into. Additionally, if serial numbers are implemented on the device's model, all devices of the same model must have unique serial numbers. USB serial numbers maybe optional for other device classes unless the device class or required user experience make it necessary. Host Wire Adapters and Device Wire Adapters (Class Code 0圎0, subclass 02).Communication device class (Class Code 0x02).Bluetooth (Class Code 0圎0, SubClass 0x01, Protocol 0x01).
USB serial numbers must be implemented for the following device classes: This requirement validates that USB serial numbers are implemented for specific device classes and are unique across specific device models. Device.Connectivity additional documentation.Tests in this feature area might have additional documentation, including prerequisites, setup, and troubleshooting information, that can be found in the following topic(s): This test verifies that device serial numbers are unique.