Features of a switch and how it makes the hub obsolete

The hub works at the physical layer, so it is relatively stupid and cannot recognize MAC frames. Dumb operation, all bytes received on one port are copied to other ports, so it will have performance issues. In addition, only one host can communicate at the same time. If too many hosts communicate at the same time, conflicts will occur. From this point of view, hubs have many problems, but one advantage is that they are cheap. The previous switches were expensive, so hubs were not eliminated at that time.

Characteristics of switches

Compared with hubs, switches have many advantages, such as supporting full-duplex communication, autonomous learning capabilities, etc., as follows Let’s take a look at the characteristics of the switch:

Multi-port: Switches usually have many interfaces, each interface is connected to one host or another switches, and usually operate in full-duplex mode.

Exclusive transmission media, collision-free data transmission: This is the main advantage of the switch. The switch has parallelism, that is, it can connect multiple pairs of interfaces at the same time, allowing multiple pairs of hosts to communicate at the same time. Moreover, the communication between these hosts uses the exclusive transmission medium and transmits data without collision.

If 10 hosts in 100Mbit/s LAN A are connected through a hub, then the average bandwidth occupied by these hosts is only 10Mbit/s. If the hosts in 100Mbit/s LAN B are connected through a switch, then because the hosts in the switch exclusively occupy the transmission media, the unoccupied space is still 100Mbit/s. The total capacity of a switch with 10 interfaces is 1000Mbit/s.

Store and forward: Each interface of the switch has a memory, which is used to store the received data packets and then forward them to another port.

Autonomous learning capability: The switch can learn independently and establish an internal switching table. In layman's terms, independent learning is the process of getting to know the host connected to the interface. Once you know the host on the interface, you don't need to broadcast when communicating one-to-one.

After introducing the characteristics of switches, we can find that switches have huge advantages compared with hubs. It is equivalent to a smart phone compared to an elderly phone, suppressing all aspects. Therefore, when the price of switches became very cheap, hubs rested peacefully and withdrew from the stage of history.

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