Network Switch Knowledge Summary

Published by Harmony January 16,2020

A switch means "switch" is a network device used for electrical (optical) signal forwarding. It provides an exclusive electrical signal path for any two network nodes that access the switch. The most common switch is an Ethernet switch. Other common telephone voice switches, fiber switches, and so on.


Network switch classification


Ethernet switch


With the rapid development of computers and their interconnected technologies (also known as "network technologies"), Ethernet has become the most popular short-distance two-layer computer network to date. The core component of Ethernet is the Ethernet switch.


Whether it is manual switching or program-controlled switching, it is to transmit voice signals, which is a "circuit switching" that requires exclusive lines. Ethernet is a computer network that needs to transmit data, so it uses "packet switching." But no matter which switching method is adopted, the switch will not change the feature of providing "exclusive access" between two points. In the case of Ethernet devices, the essential difference between a switch and a hub is that when A sends a message to B, if it passes through a hub, all network nodes accessing the hub will receive this message (that is, it is sent by broadcast). Only the NIC will filter out the information that is not sent to the machine at the hardware level; if it passes through the switch, unless A notifies the switch to broadcast, the information C sent to B will never be received (obtaining the control permission of the switch to monitor the situation) except).


Ethernet switch vendors have introduced three or even four-layer switches based on market demand. But in any case, its core function is still the Layer 2 Ethernet packet exchange, but with a certain ability to handle IP layers and even higher layers of data packets. A network switch is a network-enhancing device that provides more ports in a subnet to connect more computers. With the development of the communication industry and the advancement of national economy information, the network switch market has shown a steady upward trend. It is characterized by high performance and price ratio, high flexibility, relatively simple and easy to implement.


Optical switch


Optical switching is the next generation of switching technology that people are developing. All switching technologies are based on electrical signals. Even a fiber-optic switch converts an optical signal into an electrical signal. After being exchanged, it is switched back to the optical fiber and sent to another optical fiber. Since the photoelectric conversion rate is low and the processing speed of the circuit has a physical bottleneck, it is desirable to design an "optical switch" that does not require photoelectric conversion. The internal circuit is not an electric circuit but the optical path is not a switching circuit. It is the switch light path. This will greatly increase the processing speed of the switch.



Network switch function


The main functions of the network switch include physical addressing, network topology, error checking, frame sequence, and flow control. At present, the switch also has some new features, such as support for VLAN (Virtual Local Area Network), support for link aggregation, and even some have firewall functions.


In addition to being able to connect to the same type of network, switches can also interconnect between different types of networks, such as Ethernet and Fast Ethernet. Many switches today offer high-speed ports that support Fast Ethernet or FDDI to connect to other switches in the network or to provide additional bandwidth for critical servers with large bandwidth.


In general, each port of the switch is used to connect to a separate network segment, but sometimes in order to provide faster access speed, we can connect some important network computers directly to the ports of the switch. In this way, the network's key servers and important users have faster access speeds and support greater traffic.


Learning function: The Ethernet switch knows the MAC address of the device connected to each port, and maps the address to the corresponding port and stores it in the MAC address table in the switch cache.


Forwarding filtering: When the destination address of a data frame is mapped in the MAC address table, it is forwarded to the port connected to the destination node instead of all ports (if the data frame is a broadcast/multicast frame, it is forwarded to all ports).