What are the respective roles of repeaters and hubs in a network, in detail?

Repeaters have the role of amplifying signals; they are actually a signal regeneration amplifier. Repeaters are thus used to extend the length of LAN segments and drive long-distance communications. The most typical application of repeaters is to connect more than two Ethernet cable segments, and its purpose is to extend the length of the network. However, the extension is limited, and repeaters can only work effectively within a defined signaling delay. For example, the famous "5-4-3" rule for Ethernet: Ethernet has up to five segments connected by four repeaters, and in order to prevent conflicts, only up to three segments can be connected for operation. Repeaters have some of the following characteristics: (1) Repeaters are used in the physical layer, often used in the bidirectional forwarding of physical signals between two network nodes. Responsible for the physical layer of the two nodes in the physical layer by bit to transfer information, complete the signal copy, adjust and amplify the function, in order to extend the length of the network. For example, 502.3 Ethernet-to-Ethernet connections and 802.5 token ring-to-token ring networks. LANs connected by repeaters are physically one network, that is, repeaters interconnect multiple independent physical networks into one large physical network. (2) Repeaters can connect similar LANs with the same transmission medium (e.g., Ethernet over thick coaxial cable to each other), or similar LANs with different transmission mediums (e.g., Ethernet over thick coaxial cable to Ethernet over thin coaxial cable, or Ethernet over thick coaxial cable to Ethernet over dual-core cable). coaxial cable Ethernet and twisted pair Ethernet are interconnected). (3) Repeater interconnections are realized in the physical layer, so it is completely transparent to the protocols above the physical layer (data link layer to the application layer), that is to say, the repeater supports any protocols in the data link layer and the layers above it.2. Ethernet Hub (Hub) Hub's main function is to regenerate and plasticize and amplify the received signals in order to expand the transmission distance of the network, and at the same time, put all the nodes in the nodes that are centered on it. center of the node. Characteristics of a hub: (1) amplifies signals; (2) propagates signals through the network; (3) no filtering; (4) no path detection or switching; (5) serves as a centralized connection point for Ethernet; and (6) hubs of different rates cannot be cascaded. The advantage of using a hub as a node center is that when a line or a node in the network system fails, it will not affect the normal operation of other nodes on the network. Disadvantages of hubs: (1) user bandwidth *** enjoyment, bandwidth constraints; (2) broadcast method, easy to cause network storms; (3) non-duplex transmission, network communication efficiency is low. Classification of hubs: (1) According to the transmission rate (i.e., the bandwidth supported by the hub), it can be divided into three types: 10Mbps, 100Mbps and 10Mbps/100Mbps adaptive. (2) According to the different forms of configuration, the hub can be divided into three categories: stand-alone, modular and stacked, and stacked hubs (3) According to the different ways in which the hub works, it can be divided into passive hubs, active hubs and intelligent hubs. (4) in accordance with the hub of the data signal management, can be divided into: switching, *** enjoyment and stackable *** enjoyment of three kinds. Stacked *** enjoy hub if a network of all the devices are connected by just one cable, or network segments by the hub and other non-filtering capabilities of the device is connected, there may be more than one user at the same time to send data to the network, caused by more than one node tries to send data at the same time, a data conflict will occur. When a conflict occurs, the data sent from each device collides with each other and gets corrupted. The area of the network where packets are generated and conflicts occur is called the conflict domain.