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A switch is a network device used for electrical signal forwarding. It can provide an exclusive electrical signal path for any two network nodes of the access switch. The most common switch is an Ethernet switch. Other common ones are telephone voice switches and fiber switches. Exchange is a collective term for technologies that send information to be transmitted to the corresponding routing that meets the requirements according to the needs of the two ends of the communication to transmit information, using manual or automatic equipment. The switches can be divided into WAN switches and LAN switches according to different working positions. A wide-area switch is a device that performs information exchange functions in a communication system. It is applied at the data link layer. The switch has multiple ports, each of which has a bridging function, and can be connected to a LAN or a high-performance server or workstation. In fact, switches are sometimes referred to as multi-port bridges.
What is a switch product loop
In large-scale LAN networks, network channels are often severely blocked. There are many reasons for this failure, such as network virus attacks, network equipment hardware damage, and network bottlenecks. Changes or changes in the network are the most prone to failures, because frequent network changes can easily cause network loops, and network congestion caused by network loops often has a strong concealment, which is not conducive to failure. Efficient exclusion.
What is the purpose of the switch
The main functions of the switch include physical addressing, network topology, error checking, frame sequence, and flow control. The switch also has some new functions, such as support for VLAN (virtual local area network), support for link aggregation, and some even have firewall functions. The history of electrical handshaking should go back to the early days of the telephone. When the phone was invented, it only needed a long enough wire, plus two phones at the end, to enable two people who were far apart to have a voice conversation.
1. From the perspective of the OSI architecture, the hub belongs to the first layer of the physical layer device, and the switch belongs to the second layer of the data link layer device of the OSI. In other words, the hub only plays a role of synchronization, amplification, and shaping of data transmission. It cannot effectively process short frames = fragments in data transmission, and cannot guarantee the integrity and correctness of data transmission. The switch not only can Data transmission is synchronized, amplified, and shaped, and short frames, fragments, etc. can be filtered.
2. Judging from the working mode, the hub is a broadcast mode, that is, when one port of the hub is working, all other ports can listen to the information, which is prone to broadcast storms. When the network is large, the network performance will be greatly affected. The switch can avoid this phenomenon. When the switch is working, only the requesting port and the destination port respond to each other without affecting other ports. Therefore, the switch can isolate the collision domain and effectively suppress the occurrence of broadcast storms.
3． In terms of bandwidth, no matter how many ports the hub has, all ports share a bandwidth. Only two ports can transmit data at the same time, and other ports can only wait. At the same time, the hub can only work in half-duplex mode. For the switch, each port has an exclusive bandwidth. When two ports work, it does not affect the work of other ports. At the same time, the switch can work not only in half-duplex mode but also 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 communications. LAN switches are used in local area networks to connect terminal devices such as PCs and network printers. It can be divided into Ethernet switches, Fast Ethernet switches, Gigabit Ethernet switches, FDDI switches, ATM switches and token ring switches from the perspective of transmission media and transmission speed. In terms of scale applications, it can be divided into enterprise-level switches, department-level switches, and workgroup switches. The dimensions of each manufacturer's division are not completely the same. Generally speaking, enterprise-level switches are rack-type, department-level switches can be rack-type (with fewer slots), or fixed-configuration. Class switch is fixed configuration (function is relatively simple).
On the other hand, from the perspective of the scale of the application, as a backbone switch, the switches supporting large-scale enterprise applications with more than 500 information points are enterprise-level switches, and the switches supporting medium-sized enterprises with less than 300 information points are department-level switches, while supporting 100 The switches within this information point are workgroup-level switches. The switches described in this article refer to LAN switches.
What is an Ethernet machine
With the rapid development of computers and their interconnection technology (also commonly known as "network technology"), Ethernet has become the short-distance two-tier computer network with the highest penetration rate so far. The core component of Ethernet is the Ethernet switch.
Regardless of whether it is manual or program-controlled switching, it is to transmit voice signals, and it is a "circuit switching" that requires exclusive lines. Ethernet is a computer network that needs to transmit data, so it uses "packet switching." However, no matter what kind of switching method is adopted, the feature that the switch provides an "exclusive path" between two points will not change. As far as Ethernet equipment is concerned, the essential difference between a switch and a hub is that when A sends a message to B, if it passes through the hub, all network nodes connected to the hub will receive this message (that is, sent in broadcast form) , But the network card will filter out the information not sent to the machine at the hardware level; and if it passes the switch, unless the A informs the switch to broadcast, the message C sent to B will never be received. except).
Ethernet switch manufacturers have launched Layer 3 or even Layer 4 switches according to market demand. However, its core function is still Layer 2 Ethernet data packet exchange, but with a certain ability to process IP layer and even higher layer data packets. A network switch is a device that expands the network and can provide more connection ports in a subnet in order to connect more computers. With the development of the communications industry and the advancement of the national economy informatization, the network switch market is steadily rising. It has the characteristics of high cost performance, high flexibility, relatively simple, and easy to implement.
What is an optical switch
Optical switching is the next-generation switching technology being developed. All switching technologies are based on electrical signals. Even fiber-optic switches first convert optical signals into electrical signals. After the switching process, the optical signals are sent back to another optical fiber. Due to the low photoelectric conversion rate and the physical bottleneck of the processing speed of the circuit, people want to design a kind of "optical switch" that does not need to undergo photoelectric conversion. Its internal circuit is not a circuit but an optical path, and the logic element is not a switching circuit. It is the switching optical path. This will greatly increase the processing speed of the switch.
Example of a 24-port Gigabit switch:
The first is whether to support PoE power supply. This technical indicator is often ignored by most people, because the access layer switch is directly connected to the terminal. The biggest advantage of the PoE power supply 24 port switch is that it can easily access other devices.
In today's corporate LANs, terminal devices are no longer limited to computers, wireless APs or IP phones, IP cameras, etc., will be connected to the switch. These devices are often installed in places where it is not convenient to access power, such as walls, ceilings, etc. .
If the 24-port switch does not support the PoE power supply function, the network administrator can only replace the switch. Therefore, when purchasing a switch, consider directly purchasing a PoE-powered switch, saving time and effort. In terms of PoE power supply, there is another indicator that needs attention: the power provided by each port. Generally speaking, the PoE function uses the 802.3af standard. This standard specifies five levels of electrical power requirements from 3.84 to 12.95W. More than 13W. However, because different APs, IP phones, or cameras require different amounts of power, when choosing a 24-port switch, the larger the PoE power provided by each port, the better.
The second is the number of VLANs supported and the number of ports aggregated. Dividing different VLANs for each workgroup is the most familiar operation for network administrators. The same is a 24-port switch, but the number of VLANs supported is very different, some support 64, and some can be up to 256. Obviously, the larger this number is, the better, and more VLANs can be divided.
The third data to note is the number of MAC address tables. The so-called number of MAC addresses refers to the maximum number of MAC addresses that can be stored in the 24-port switch's MAC address table. The more MAC addresses are stored, the higher the speed and efficiency of data forwarding. But different grades of switches can support different numbers of MACs per port. At each port of the switch, sufficient buffers are needed to memorize these MAC addresses, so the size of the buffer (buffer) capacity determines how many MAC addresses the corresponding switch can memorize. Generally, a switch can basically memorize 1024 MAC addresses, and a general switch can usually do this. However, if the future expansion of the enterprise network is taken into consideration, the number of the MAC address table should be larger, so that when the capacity is expanded, there are more options, and the switch will not be replaced frequently, thereby greatly reducing the total cost of ownership of the switch.
The fourth value is the backplane bandwidth. The larger the value, the better. The larger the backplane bandwidth, the stronger the forwarding capability of the 24-port switch. However, the backplane bandwidth is generally related to the number and rate of ports. The calculation formula is port. Number * Corresponding port rate * 2 (full-duplex mode) If the total bandwidth ≤ the nominal backplane bandwidth, then the backplane bandwidth is wire-speed. Obviously, when a 24-port switch is selected, as long as the number of 100M ports and Gigabit ports is considered, the value of the backplane bandwidth can be calculated. Therefore, when choosing a switch, it doesn't make much sense if the backplane bandwidth number is large. As long as the port speed meets your requirements and the working mode can support full duplex.
The fifth thing to note is the QoS function. Today's LANs are not only data, but also IP voice and video transmission. In addition, some employees often use the company network to download some non-working content such as movies and SNS games. These will occupy the bandwidth of the LAN, which will affect the work of others. Although network administrators can manage the behavior of these users by purchasing professional equipment such as online behavior management and traffic management, for small companies' limited budgets, the purchase of these devices may not be approved by the management of the enterprise. At this time, choose A 24-port switch with QoS function can solve the urgent needs of network administrators to a certain extent.
The sixth is the Web management interface. The configuration and management of the Web interface is very convenient and easy to operate, which greatly reduces the configuration workload for the network management.
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