Final answer:
A USB hub supports up to 127 devices through a combination of direct connections and cascading additional hubs, with the caveat that practical limits may be lower.
Step-by-step explanation:
A universal serial bus (USB) hub allows multiple USB devices to be connected to a single USB port on a host system. Under standard specifications, a single USB host controller through a root hub can support up to 127 devices, including the hub itself. It achieves this through a combination of cascading additional hubs and the devices connected directly to the hubs. However, it's important to remember that each hub introduces a small amount of latency and potentially reduces the available bandwidth for each device, so practical limits are often lower than 127 devices, depending on the types and uses of the devices connected.