Basic Network Learning: Approaching vswitches (1)

Understanding and mastering the knowledge and skills of vswitches has become a basic symbol of the level of network administrators. Therefore, this article will introduce the basic knowledge related to vswitches, this gives you a basic and comprehensive understanding of the basic knowledge and applications of vswitches.

I. vswitch Basics

As the first type of widely used network cabling equipment, hubs were widely used in various local area networks. However, with the increasing variety of media types transmitted over the network and the emergence of multimedia content such as graphics, images, and various streaming media, people are increasingly demanding high network data transmission speeds and transmission performance. Because of its shared media transmission, ticket data operation, and broadcast data transmission methods, the hub naturally determines that it is difficult to meet the above-mentioned speed and performance requirements. With the help of users and the efforts of major network equipment developers around the world, a new and more practical set-line device, vswitch, has emerged. The vswitch completely overcomes the above shortcomings of the hub, so it has been widely recognized and applied in the industry in a short time. The switch technology has also developed rapidly, and the speed of data transmission is also growing rapidly. Currently, the fastest Ethernet switch supports 10 Gbit/s and Gbit/s.

The English name of a vswitch is "Switch". It is an upgraded product of a hub. In terms of appearance, it is basically no different from a hub, all are rectangular boxes with multiple ports. A vswitch is a technology collectively referred to as a technology that sends the information to be transmitted manually or automatically by devices to a route that meets the requirements. A vswitch in the broad sense is a device that implements information exchange in a communication system.

The "switch" and "switch" were first originated from the telephone communication system PSTN ). We used to see some old movies in movies or TV and often see people shake a few times by the phone. Note that it is not a dial-up.) then we said, "Pick up XXX with me, after receiving the request, the telephone operator inserts the corresponding terminal line header on the terminal to call. In fact, this is the most original telephone switch system, but it is not an automatic or computer switch that we are going to talk about today, however, the computer switch we want to talk about now is developed in this telephone switch technology.

In computer network systems, the concept of exchange is improved compared with the shared working mode. We know that a HUB is a network device that shares media, and the HUB itself cannot identify the destination address. It is sent to all nodes in broadcast mode. That is, when host A in the same LAN transmits data to host B, data packets are transmitted in broadcast mode on A HUB-based network, and the same information is sent to all nodes on the network at the same time, then, each terminal verifies the address information of the data packet header to determine whether to receive the packet. In this way, we know that it is easy to cause network congestion, because in fact, there is generally only one terminal node to receive data, and now all nodes are sent, so most of the data traffic is invalid, in this way, the entire network data transmission efficiency is quite low. On the other hand, because each node can listen to the sent data packet, it is obviously not safe, and it is prone to some insecure factors.

The vswitch has a high-bandwidth back bus and an internal switching matrix. All ports of the vswitch are attached to the back bus. After the control circuit receives the packet, the processing port will look for the hardware address of the MAC address NIC In the memory) comparison table to determine the NIC of the target MAC) connected to which port, the data packet is directly transmitted to the target node through the internal switching matrix, instead of all nodes. If the target MAC does not exist, it is broadcast to all ports. In this way, we can clearly see that, on the one hand, the efficiency is high and network resources are not wasted, but data is sent to the destination address, which is generally not prone to network congestion. On the other hand, data transmission is secure, because it does not send data to all nodes at the same time, it is difficult for other nodes to listen to the sent information when sending data. This is one of the important reasons why the switch quickly replaces the hub.

Another important feature of a vswitch is that it does not share the bandwidth of each port like a hub. Each port of a vswitch shares the total bandwidth of a dedicated vswitch, this guarantees the speed of each port. In addition, you can also use a vswitch to segment the network. By comparing the address table, the switch only allows necessary network traffic to pass through the vswitch, which is the VLAN Virtual LAN to be introduced later ). Through the filtering and forwarding of vswitches, the broadcast storm can be effectively isolated to reduce the occurrence of incorrect packets and wrong packets, so as to avoid sharing conflicts. In this way, the switch can transmit data between multiple nodes at the same time. Each node can be considered as an independent network segment, the network devices connected to them enjoy a fixed bandwidth and do not need to compete with other devices. For example, when node A sends data to node D, Node B can send data to node C at the same time, and both transmission enjoy bandwidth and both have their own virtual connections. For example, if you are using a 10 Mbps 8-port ethernet switch, because each port can work at the same time, when the data traffic is large, the total traffic can reach 8*10 Mbps = 80 Mbps, but when using a 10 Mbps shared HUB, it is a shared bandwidth, therefore, only one port can be allowed for communication at the same time, and the total traffic of the HUB will not exceed 10 Mbps if the data traffic is busy. If it is port 16 or port 24, it is even more obvious!

The main functions of a vswitch include physical addressing, network topology, error verification, frame sequence, and traffic control. At present, some high-end switches also have some new functions, such as support for VLAN Virtual LAN), support for Link aggregation, and even some have routing and firewall functions.

In addition to connecting to the same type of network, a vswitch can also interconnect different types of networks, such as Ethernet and Fast Ethernet. Nowadays, many vswitches can provide high-speed connection ports that support fast Ethernet or FDDI. These ports are used to connect other vswitches in the network or provide additional bandwidth for key servers with high bandwidth usage.

Generally, each port of a vswitch is used to connect to an independent network segment. However, to provide faster access speed, we can directly connect some important network computers to the port of the vswitch. In this way, the key servers and important users of the network have a faster access speed and support greater information traffic.

In short, a vswitch is a network device that can encapsulate and forward data packets based on MAC address recognition. The switch will send packets that fail to be sent to the destination address for the first time to all nodes at the same time in an attempt to find the destination MAC address, after finding the address, it will be added to its MAC address list, so that no error will be sent the next time it is sent to this node. This function of a vswitch is called the "MAC address learning" function.

Ii. Differences between vswitches and hubs

As we mentioned above, the vswitch was initially designed to solve the problem of hub shared transmission media. The port bandwidth is too narrow, which is prone to broadcast storms, the first switch was the Layer 2 switch in the OSI/RM open architecture, so we will continue to introduce the switch classification in the next article ). This section describes the differences between a vswitch and a hub. In other words, what are the advantages of a vswitch, after understanding the differences between them, we can correctly understand why vswitches are widely used in the current LAN, rather than hubs, and make it easier for us to choose the right option for future network devices.