By PURPLELEC | 25 July 2023 | 0 Comments
The working principle and function of the hub
A hub is a pure hardware network bottom layer device, mainly a device that connects multiple Ethernets or optical fibers together under the same physical medium. When the hub is in operation, it is mainly used as a multi-port repeater. If a collision is detected, a blocking signal will be submitted.
The working principle of the hub
The working principle of the hub is mainly to convert signals and work on the physical layer of the OSI/RM reference model and the MAC (media access control) sublayer of the data link layer. Among them, the physical layer well defines electrical signals, symbols, line states, and clock requirements, while performing data encoding and connectors for data transmission. Because the hub only shapes and amplifies the signal and then retransmits it without encoding, it is a physical layer device.
To put it simply, a hub sends a signal to the line first, and the hub starts to receive such a signal. Therefore, the signal is attenuated during the cable transmission process. After receiving the signal, the attenuated signal is shaped and amplified, and finally the hub broadcasts the amplified signal to all other ports.
The role of the hub
1. Each station is connected to the hub with its own dedicated transmission medium. There is no longer only one transmission channel between each node. The signals sent back by each node are collected through the hub, and the hub reshape and amplifies the signal and send it to all nodes. In this way, there will be no collisions on the uplink channel.
2. The hub does not have the MAC address table that the switch has, so when it sends data, it is not targeted, but is sent by broadcast. In other words, when it wants to send data to a node, it does not directly send the data to the destination node, but sends the data packet to all nodes connected to the hub.
3. When the hub detects a collision from its internal port, a collision enhancement signal (jam) is generated and transmitted to the target port to which the hub is connected. At this time, all data cannot be sent successfully, forming a "big traffic jam" in the network.
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