As the name implies, the function of the Hub is to gather the network cables together, which is called "hub" in English. "Hub" means "center". The main function of the hub is to regenerate, shape and amplify the received signal, so as to expand the transmission distance of the network, and at the same time concentrate all nodes on the node centered on it. It works in the first layer of the OSI (open system interconnect) reference model, that is, the "physical layer".