Network hub
The hub works in a local area network (LAN) environment. Like a network card, it is applied to the first layer of the OSI reference model, so it is also called a physical layer device. Electrical interconnection is adopted inside the hub. When the environment for maintaining the LAN is a logical bus or ring structure, the hub can be used to establish a physical star or tree network structure. In this respect, the hub acts as a multi port repeater. In fact, the hub is actually a kind of repeater. The only difference is that the hub can provide more port services, so the hub is also called multi port repeater.