A network switch is a network-expanding device that provides more ports for sub-networks to connect to 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. Therefore, Ethernet technology has become the most important LAN networking technology today, and network switches have become the most popular switches.
Broadly speaking, switches are divided into two types: WAN switches and LAN switches. WAN switches are mainly used in the telecommunications field to provide a communication infrastructure platform. LAN switches are used in local area networks to connect terminal devices such as PCs and network printers.
According to the current complex network configuration, network switches are divided into access layer switches, aggregation layer switches, and core layer switches. Among them, the core layer switches all adopt the chassis modular design, and basically have designed the 1000base-T module equipped with them. The Ethernet switch supporting the 1000base-T at the access layer is basically a fixed port switch, which is mainly a 10/100M port and provides a 1000base-T uplink port in a fixed port or an expansion slot. The aggregation layer 1000base-T switch has both chassis and fixed port designs, and can provide multiple 1000base-T ports. Generally, other types of ports such as 1000base-X can also be provided. The access layer and the aggregation layer switch together form a complete small and medium-sized LAN solution.
From the perspective of transmission media and transmission speed, LAN switches can be divided into Ethernet switches, Fast Ethernet switches, Gigabit Ethernet switches, FDDI switches, ATM switches, and Token Ring switches. These switches are suitable for Ethernet. , Fast Ethernet, FDDI, ATM, and Token Ring.
From the scale application, there are enterprise switches, departmental switches, and workgroup switches. The scale of each vendor is not completely consistent. Generally speaking, enterprise switches are rack-mounted, department-level switches can be rack-mounted or fixed-configuration, and work-group switches are generally fixed-configuration. The function is relatively simple. 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.
According to the characteristics of the architecture, people also divide the LAN switch into three types: rack-mounted, fixed-distribution configuration with expansion slot and fixed configuration without expansion slot. A rack switch is a slot-type switch that is scalable and supports different network types such as Ethernet, Fast Ethernet, Gigabit Ethernet, ATM, Token Ring, and FDDI. But the price is more expensive. Many high-end switches use a rack-mount structure. A fixed-configuration switch with an expansion slot is a switch with a fixed port and a small number of expansion slots. This switch can support other types of networks by extending other network type modules based on a fixed-port type network. The price of the switch is centered. A fixed-profile switch without expansion slots supports only one type of network (typically Ethernet) and can be used in local area networks in small businesses or office environments at the lowest price and most widely used.
According to OSI’s seven-layer network model, switches can be divided into Layer 2 switches, Layer 3 switches, Layer 4 switches, etc., up to Layer 7 switches. Layer 2 switches based on MAC address work are most common and are used in the network access layer and aggregation layer. Layer 3 switches based on IP addresses and protocols are commonly used in the core layer of the network and are also used in small amounts in the aggregation layer. Some Layer 3 switches also have a Layer 4 switching function, which can perform target port judgment based on the protocol port information of the data frame. The switches above the fourth layer are called content switches and are mainly used in Internet data centers.
According to the manageability of the switch, the switch can be divided into a manageable switch and an unmanaged switch. The difference is that it supports SNMP, RMON, and other network management protocols. Manageable switches facilitate network monitoring and traffic analysis, but at a relatively high cost. At present, manufacturers of managed switches on the market include major network equipment suppliers such as Huawei, Cisco, and Flying Fish. Large and medium-sized networks should choose manageable switches at the aggregation layer. Depending on the application needs at the access layer, the core switches are all manageable switches.
According to whether the switch can be stacked, the switch can be divided into two types: a stackable switch and a non-stackable switch. One of the main purposes of designing stacking technology is to increase port density.
According to the most common general classification method, LAN switches can be classified into three types: desktop switches, workgroup switches, and campus switches. The desktop switch is the most common type of switch, and it is the most widely used, especially in the general office, small computer room and business department with relatively concentrated business acceptance, multimedia production center, website management center and other departments. In terms of transmission speed, modern desktop switches mostly provide multiple ports with 10/100M adaptive capabilities. Workgroup switches are often used as expansion devices. When desktop switches fail to meet the needs, most workgroup switches are directly considered. Although the workgroup switch has only a small number of ports, it supports more MAC addresses and has good expansion capability. The transmission speed of the port is basically 100M. Campus network switches are relatively rare and are only used in large networks. They are generally used as backbone switches of the network and have fast data exchange capability and full-duplex capability. They provide intelligent features such as fault tolerance, and also support expansion options and Layer 3. Multiple functions such as virtual local area network (VLAN) in the exchange.
According to different switching technologies, some people divide switches into port machines, frame switches, and cell switches. Unlike bridges, switch forwarding delays are small, and operations are close to the single-LAN performance, far exceeding the forwarding performance between ordinary bridged Internet. Switching technology first appeared in slot-type hubs. The backplanes of such hubs are usually divided into multiple Ethernet segments, which are not connected by bridges or routers. The networks are not connected to each other. After the Ethernet main module is inserted, it is usually assigned to the network segment of a backplane. The switch is used to allocate and balance the ports of the Ethernet module between multiple network segments on the backplane. Frame switching is currently the most widely used LAN switching technology. It provides a parallel transmission mechanism by micro-segmenting the traditional transmission medium to reduce the collision domain and obtain high bandwidth. ATM technology represents a “good medicine” for many of the challenges in networking and communications. ATM uses a cell exchange with a fixed length of 53 bytes. Due to the fixed length, it is easy to implement in hardware. ATM uses dedicated, non-differential connections to run in parallel, allowing multiple nodes to be established simultaneously through a single switch, without affecting the communication capabilities between each node. ATM also allows communication capabilities between the source node and the target node. ATM uses statistical time-division circuits for multiplexing, which can greatly improve channel utilization. ATM bandwidth can reach 25M, 155M, 622M or even several G-bit transmission capabilities.
In fact, from the application point of view, switches can be divided into telephone switches (PBX) and data switches (Switch). Of course, the current very fashionable voice over the data transmission VoIP is also known as the “soft switch.”
In accordance with the divergent operation mode when the AC machine processes frames, it can be divided into two categories:
Store and forward: The AC must receive the entire frame before forwarding, and perform error check. If there is no error, send the frame to the destination address. The forwarding delay of the frame via the alternator changes with the divergence of the frame length.
Longitudinal: The AC will forward the frame as soon as it detects the destination address contained in the frame header, and does not need to expect the full number of frames to be accepted. Because the length of the Ethernet frame header is always fixed, the forwarding delay of the frame through the exchange is also unchanged.
