What is the use of the switch?

1. From the perspective of the OSI architecture, the hub belongs to the first layer of physical layer equipment, and the switch belongs to the second layer of data link layer equipment of the OSI. That is to say, the hub only plays a role in synchronizing, amplifying and shaping the data transmission. The short frame=fragment in the data transmission cannot be effectively processed, and the integrity and correctness of the data transmission cannot be guaranteed; Synchronize, amplify, and shape the data, and filter short frames, fragments, and so on.

2. From the perspective of working mode, the hub is a broadcast mode. That is to say, when a certain port of the hub works, all other ports can listen to the information, which is easy to generate a broadcast storm. When the network is large, the network performance is greatly affected. The switch can avoid this phenomenon. When the switch works, only the requesting port, and the destination port respond to each other without affecting other ports, so the switch can isolate the collision domain and effectively suppress the occurrence of broadcast storms.

3. From the perspective of bandwidth, no matter how many ports a hub has, all ports share a bandwidth. Only two ports can transmit data at the same time, other ports can only wait, and the hub can only work in half-duplex mode; For a switch, each port has an exclusive bandwidth. When two ports work, it does not affect the operation of other ports. At the same time, the switch can work in half-duplex mode and can work in full-duplex mode.

Broadly speaking, there are two types of network switches: WAN switches and LAN switches. WAN switches are mainly used in the telecommunications field to provide a basic platform for communication. LAN switches are used in local area networks to connect terminal devices such as PCs and network printers. From the transmission medium and transmission speed, it can be divided into Ethernet switches, Fast Ethernet switches, Gigabit Ethernet switches, FDDI switches, ATM switches, and Token Ring switches. From the scale application, it can be divided into enterprise-level switches, department-level switches, and workgroup switches. The scale of each vendor is not completely consistent. Generally speaking, enterprise switches are rack-mounted, and department-level switches can be rack-mounted (a small number of slots) or fixed configuration, and working groups. The level switch is a fixed configuration (simplified function).

On the other hand, from the perspective of the scale of the application, when it is a backbone switch, the switch supporting large enterprise applications with more than 500 information points is an enterprise-class switch, and the switch supporting medium-sized enterprises with 300 information points or less is a department-level switch and supports 100. The switches within the information points are workgroup switches. The switch described in this document refers to a LAN switch.


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