wires that were intended for flip-flop capabilities of the USB-C connector. USB 3.0 also introduced the USB Attached SCSI (UASP) protocol, which provides generally faster transfer speeds than the BOT (Bulk-Only-Transfer) protocol. Naming scheme Starting with the USB 3.2 standard, USB-IF introduced a new naming scheme. To help companies with branding of the different transfer modes, USB-IF recommended branding the 5, 10, and 20 Gbit/s transfer modes as SuperSpeed USB 5Gbps, SuperSpeed USB 10Gbps, and SuperSpeed USB 20Gbps, respectively. As of September 2022, this naming scheme is deprecated. USB4 The USB4 specification was released on 29 August 2019 by the USB Implementers Forum. USB4 is based on the Thunderbolt 3 protocol. It supports 40 Gbit/s throughput, is compatible with Thunderbolt 3, and backward compatible with USB 3.2 and USB 2.0. The architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application. The USB4 specification states that the following technologies shall be supported by USB4: During CES 2020, USB-IF and Intel stated their intention to allow USB4 products that support all the optional functionality as Thunderbolt 4 products. The first products compatible with USB4 are expected to be Intel's Tiger Lake series and AMD's Zen 3 series of CPUs. Released in 2020. The USB4 2.0 specification was released on 1 September 2022 by the USB Implementers Forum. September 2022 naming scheme Because of the previous confusing naming schemes, USB-IF decided to change it once again. As of 2 September 2022, marketing names follow the syntax "USB XGbps", where X is the speed of transfer in Gb/s. Overview of the updated names and logos can be seen in the adjacent table. Version history Release versions Power-related standards System design A USB system consists of a host with one or more downstream ports, and multiple peripherals, forming a tiered-star topology. Additional USB hubs may be included, allowing up to five tiers. A USB host may have multiple controllers, each with one or more ports. Up to 127 devices may be connected to a single host controller. USB devices are linked in series through hubs. The hub built into the host controller is called the root hub. A USB device may consist of several logical sub-devices that are referred to as device functions. A composite device may provide several functions, for example, a webcam (video device function)