USB device classes are categories of devices with similar characteristics and that perform common functions. Those classes and their specifications are defined by the USB-IF. Each device class is identified by USB-IF approved class, subclass, and protocol codes, all of which are provided by the IHV in device descriptors in the firmware.

USB communications device class (or USB CDC) is a composite Universal Serial Bus device class. The communications device class is used for computer networking devices akin to a network card, providing an interface for transmitting Ethernet or ATM frames onto some physical media.