Discussion on the origins and functions of Ethernet Switches

We often use Ethernet switches, in fact, originated from the telephone communication system, but in computer network systems, the concept of switching is to improve the shared working mode. What is a vswitch? Switching refers to the technology that sends the information to be transmitted manually or automatically by devices according to the needs of transmitting information at both ends of the communication. In the broad sense, an Ethernet switch is a device that implements information exchange in a communication system.

Exchange and switch originated from the telephone communication system PSTN). Now we can see this scene in the old movie: Head of the main user) Pick up the microphone and shake it for a while, the terminal is a machine with a line full of wires inserted. If the headset is worn, the service Lady inserts the line header at the corresponding exit after receiving the connection request, establishes a connection for the two clients until the call ends. This process is an exchange established manually. Of course, we have already popularized programmable switches, and the exchange process is automatically completed.

In computer network systems, the concept of exchange is an improvement of the shared working mode. The HUB we have previously introduced is A shared device. The HUB itself cannot identify the destination address. When A host in the same LAN transmits data to host B, data packets are transmitted in a HUB-based network in broadcast mode. Each terminal verifies the address information of the data packet header to determine whether to receive the data packets. That is to say, in this way, only a group of data frames can be transmitted over the network at the same time. If a collision occurs, retry. This method is shared network bandwidth.

The ethernet switch has a high-bandwidth back bus and an internal switching matrix. All ports of the Ethernet switch are attached to the back bus. After the control circuit receives the data packet, the processing port will look for the address table in the memory to determine the hardware address of the target MAC Nic) the port on which the NIC is attached. data packets are quickly transmitted to the destination port through the internal switching matrix. If the destination MAC does not exist, the packets are broadcast to all ports, after receiving the port response, the switch "learns" the new address and adds it to the internal address table.

You can also use a vswitch to segment the network. By comparing the address table, the vswitch only allows necessary network traffic to pass through the vswitch. 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.

A vswitch can transmit data between multiple port pairs at the same time. Each port can be considered as an independent network segment, and the network devices connected to it enjoy all the bandwidth alone, so they do not need to compete with other devices. When node A sends data to node D, Node B can send data to node C at the same time, and both transmission enjoy all the bandwidth of the network and all have their own virtual connections. If a 10 Mbps Ethernet switch is used here, the total traffic of the switch is 2*10 Mbps = 20 Mbps. When a 10 Mbps shared HUB is used, the total traffic of a HUB does not exceed 10 Mbps.

In short, a vswitch is a network device that can encapsulate and forward data packets based on MAC address recognition. The switch can "Learn" the MAC address and store it in the internal address table. By creating a temporary exchange path between the initiator of the data frame and the Target receiver, the data frame can directly reach the destination address from the source address.

Ethernet switch application

As the main connection device of the LAN, the Ethernet switch is one of the fastest-growing network devices. With the continuous development of switching technology, the price of Ethernet switches decreases sharply, and switching to the desktop is the trend of the times. If you have a large number of users, busy applications, and a variety of servers on the Ethernet, and you have not made any adjustments to the network structure, the performance of the entire network may be very low. One solution is to add a 10/100 Mbps switch over Ethernet. It can not only process 10 Mbps of conventional Ethernet data streams, but also support Mbps of Fast Ethernet connections.

If the network usage exceeds 40% and the collision rate exceeds 10%, the Ethernet switch can help you solve some problems. Vswitches with Mbps Fast Ethernet and 10 Mbps Ethernet ports can run in full duplex mode and can establish dedicated 20 Mbps to Mbps connections.

Not only do vswitches have different roles in different network environments, but the impact of adding new vswitches and adding switch ports of existing vswitches on the network is also different in the same network environment. Fully understanding and understanding the network traffic mode is a very important factor in whether the Ethernet switch can be used. Because the purpose of using an Ethernet switch is to minimize and filter data traffic in the network, if a switch in the network needs to forward almost all received packets due to improper installation location settings, instead of optimizing network performance, a vswitch reduces data transmission speeds and increases network latency.

In addition to the installation location, if you blindly add vswitches in networks with low load and low Information volume, it may also have a negative impact. It is more ideal to use a simple HUB than an Ethernet switch because of the processing time of data packets, the buffer size of the Ethernet switch, and the need to regenerate new data packets. Therefore, we cannot always think that a vswitch has an advantage over a HUB, especially when the user's network is not crowded and there is still a lot of available space, using the HUB can make full use of the existing resources of the network.