Detailed introduction:
Hub 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".
Hub, like network card, network cable and other transmission media, belongs to the basic equipment in local area network, and adopts CSMA/CD (carrier sense multiple access technology with collision detection) medium access control mechanism. Each interface of the hub only sends and receives bits. When it receives 1, it forwards 1, and when it receives 0, it forwards 0 without collision detection.
Hub belongs to the bottom equipment of pure hardware network, and basically does not have the ability of "intelligent memory" and "learning" similar to switches. It also has no MAC address table owned by the switch, so it sends data by broadcast, not as a target.
That is to say, when it wants to send data to a node, it does not send data directly to the destination node, but sends data packets to all nodes connected to the hub, as shown in the figure, which is simple and clear.
The hub is a multi-port repeater. When the HUB is the central equipment, one line in the network fails, which does not affect the work of other lines. Therefore, hubs have been widely used in local area networks. Most of the time, it is used in star and tree network topology, and is connected to the host through RJ45 interface (BNC interface is also available). According to different statements, there are many kinds of hubs.