Hubs provide the electrical interface between USB devices and the host. Hubs are directly responsible for supporting many of the attributes that make USB user friendly and hide its complexity from the user. Listed below are the major aspects of USB functionality that hubs must support:

			Connectivity behavior
			Power management
			Device connect/disconnect detection
			Bus fault detection and recovery
			High-, full-, and low-speed device support

A hub consists of three components: the Hub Repeater, the Hub Controller, and the Transaction Translator.

The Hub Repeater is responsible for connectivity setup and tear-down. It also supports exception handling, such as bus fault detection and recovery and connect/disconnect detect. The Hub Controller provides the mechanism for host-to-hub communication. Hub-specific status and control commands permit the host to configure a hub and to monitor and control its individual downstream facing ports. The Transaction Translator responds to high-speed split transactions and translates them to full-/low-speed transactions with full-/low-speed devices attached on downstream facing ports.