The network switch is a device that expands the network and can provide more connection ports in the sub-network to connect more computers. It has the characteristics of high performance-price ratio, high flexibility, relatively simple, and easy to implement. Therefore, Ethernet technology has become the most important LAN networking technology today, and network switches have become the most popular switches.
The role of network switches
The main functions of the switch include physical addressing, network topology, error checking, frame sequence and flow control. At present, the switch also has some new functions, such as support for VLAN (virtual local area network), support for link aggregation, and some even have the function of firewall.
In addition to being able to connect to the same type of network, the switch can also play an interconnection role between different types of networks (such as Ethernet and Fast Ethernet). Nowadays, many switches can provide high-speed connection ports that support Fast Ethernet or FDDI, etc., which are used to connect to other switches in the network or provide additional bandwidth for key servers that take up a lot of bandwidth.
Generally speaking, each port of the switch is used to connect to an independent network segment, but sometimes in order to provide faster access speed, we can connect some important network computers directly to the switch port. In this way, key servers and important users of the network have faster access speeds and support greater information flow.
Learning function: The Ethernet switch understands 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).
Elimination of loops: When the switch includes a redundant loop, the Ethernet switch avoids the loop through the spanning tree protocol and allows for the existence of backup paths.
Further study: The Ethernet AC machine tastes 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 AC machine’s cache.
Forwarding/Filtering: When the destination address of a data frame is mapped in the MAC address table, it is forwarded to the port adjacent to the destination node instead of all ports (if the data frame is a broadcast/multicast frame, it is forwarded to all ports) .
The principle of network switch
1. The switch establishes the mapping between the address and the port of the AC machine according to the source MAC address in the received data frame, and writes it into the MAC address table.
2. The switch compares the destination MAC address in the data frame with the established MAC address table to determine which port to forward.
3. If the destination MAC address in the data frame is not in the MAC address table, it is forwarded to all ports. This process is called flooding.
4. Broadcast frames and multicast frames are forwarded to all ports.
Network switch classification
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. The LAN switch is used in the local area network to connect to 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 of application, it can be divided into enterprise-level switches, department-level switches, and workgroup switches.
The scales divided by manufacturers are not completely the same. Generally speaking, enterprise-level switches are rack-mounted, and department-level switches can be rack-mounted (with fewer slots) or fixed-configuration type. Class switches are of fixed configuration type (with simpler functions). On the other hand, from the perspective of application scale, when used as a backbone switch, a switch that supports large-scale enterprise applications with more than 500 information points is an enterprise-level switch, and a switch that supports medium-sized enterprises with less than 300 information points is a department-level switch, and 100 The switches within this information point are workgroup-level switches.
Network switch purchase strategy
Today, the network is developing rapidly. In a network environment with dozens of PCs and servers (dozens of "points"), switches are already indispensable network devices. Hubs are only useful at the desktop level of the network. The place of war. But when it comes to shopping, many people can't start. This article attempts to provide some help for companies or schools to purchase network switches with the help of the analysis of switch brands and purchase tendency. Among them, it mainly involves workgroup-level and department-level switches that are used by enterprises of different sizes.
1. There is a lot of room to choose among many brands of switches
Judging from the current market, the traditional "powers" of network products-3Com and Cisco have an unshakable position. Their switch products are favored by dealers and are also the most ideal choice for users. Brand means quality assurance, technology assurance, and service assurance. This is hard to match for other brand products, but the corresponding price is naturally high. The switch prices of these brands are generally 1 to 2 times higher than those of ordinary brands.
In general IT products, high price does not mean high market share. There are many cheap and high-quality choices for commonly used PCs, printers, monitors, etc.; but network products such as routers and switches are always an exception. The higher the price of the brand, the more obvious the buying tendency. Part of the reason is that the relative technical content of routers and switches is relatively high, and the requirements for professionals are also high. Users generally have a kind of fear; and although the individual equipment of network products is expensive, the overall purchase amount is limited, so users prefer to spend Buy more money and rest assured. This phenomenon is gradually changing.
In fact, the choice of switch products is relatively large. From the perspective of domestic brands, there are Huawei, which started as network products, Shida, which has expanded from other IT products, and TCL, which has expanded from the home appliance industry; foreign and Some brands in Taiwan have also achieved better cost performance, such as Taiwan’s Netcore, which has a certain reputation and user base in China. Although these switch brands also cover a relatively complete product line, they are mainly low-end products, attracting customers with low prices and after-sales support capabilities.
2 .the most popular is the 24-port switch
The number of ports of switch equipment is the most intuitive measurement factor. Common switch ports are 8, 12, 16, 24, 48, etc. The reporter learned from some network product distributors that among workgroup-level and department-level switches, 24-port products are the most popular. For an enterprise or campus network environment with a scale of less than one hundred people, a 24-port switch can be used as a departmental switch or as a central backbone switch for the enterprise; and in terms of application, a 24-port switch is better than an 8-port and 16-port switch. The product has more room for expansion, which is beneficial to enterprises to further expand the network.
The switching speed of the switch is an important factor that determines the transmission performance of the corporate intranet. At present, 10/100Mbps fast Ethernet has become the mainstream. General switches can provide all or part of 10/100Mbps ports. Switches that provide only 10Mbps ports have gradually faded out of the market. . If the enterprise has higher requirements for the transmission speed of the local area network, it should still use the gigabit core switch as the backbone of the enterprise network, but its price is much higher than the ordinary workgroup-level switch.
3. clear distinction in price grade
Although it is said that "money is not a problem" in the eyes of some purchases, money is actually a key issue. There are huge differences in prices for switches of different brands, performance, and service capabilities. Take a 24-port switch as an example. It can be roughly divided into three grades. The prices of 3Com and Cisco are generally around 10,000 yuan, while the prices of mainland brands and some Taiwanese brands are generally below 4,000 yuan, such as Lenovo-Dlink, Shida, TP- Link etc. Among them, HRUI has a better brand awareness and a complete product line, and its switch price is about 10% higher than other products of the same grade. For general-purpose enterprises or institutions, when the price level is so obvious (almost 1:3), you may wish to focus more on domestic brands and brands in Taiwan. After all, you can save about two-thirds of the money ; If your company has sufficient funds and high requirements on the network, from the perspective of technological maturity, the HRUI brand is still the first choice.
4. Provide different types of switches according to different users
Fast Ethernet switch: Fast Ethernet is a LAN transmission standard, which provides a rate of 100Mbps (also called 100BASE-T10). Current workstations that use 10BASE-T network cards can access Fast Ethernet. (The rate that each workstation can receive is still 10Mbps). It is one of the more commonly used.
Enterprise-level switch: Enterprise-level switch is a high-end switch, which adopts a modular structure and can be used as a network backbone to build a high-speed LAN. Enterprise-level switches can provide customized customization, priority queue services, and network security control, and can quickly adapt to the needs of data growth and change, so as to meet the needs of users. For networks with more demands, enterprise-level switches can not only transmit massive amounts of data and control information, but also have hardware redundancy and software scalability features to ensure reliable network operation.
Gigabit Ethernet switch: A router with a Gigabit Ethernet interface can have a backplane that supports higher or lower Gigabit rates, and the ports connected to the backplane of the Gigabit Ethernet cache distributor share a gigabit of bandwidth. For multi-port Gigabit Ethernet switches, its high-performance backplane can support gigabit bandwidth. This will improve the efficiency of data transmission, and high-speed switches will be the development trend.
Intelligent adaptive switch: Intelligent adaptive switch is a network device that can be used for network management, which can meet your requirements for network management. Not many people and products are used.