Introduction to basic vswitch knowledge

Introduction to basic vswitch knowledge

Vswitch Definition

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. A switch in the broad sense is a device that implements information exchange in a communication system.

In the computer network system, the concept of switching improves 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.

How a vswitch works

Work on the data link layer. The vswitch has a high-bandwidth back bus and an internal switching matrix. All the ports of the vswitch are attached to the back bus. After the control circuit receives the data packet, the processing port searches for the address table in the memory to determine the target MAC address (the hardware address of the NIC) NIC is connected to which port, and 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 MAC address table.

You can also use a vswitch to segment the network. By comparing the MAC address table, the vswitch only allows necessary network traffic to pass through the vswitch. Through the filtering and forwarding of vswitches, You can effectively reduce the number of conflicting domains, but it cannot divide network-layer broadcast, that is, broadcast domains.

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.

Vswitch category

The transmission mode of the switch is full-duplex, half-duplex, full-duplex/half-duplex adaptive.

The full duplex of a switch means that the switch can receive data while sending data. The two are synchronized, as if we call each other and can hear the other party's voice while talking. All current vswitches support full duplex. The advantage of full duplex is low latency and high speed.

When talking about full duplex, we can't help but mention another concept closely related to it, that is, "Half Duplex". The so-called half duplex refers to only one action in a period of time. For example, a narrow road can only have one vehicle passing through. When two vehicles are currently on the road, in this case, only one vehicle is allowed to pass first, and the other is allowed to drive again after the first vehicle, this example illustrates the concept of half duplex. Early walkie talkie and early hub devices are half duplex products. With the continuous advancement of technology, half duplex will gradually exit the stage of history.

In a broad sense, there are two types of network switches: WAN switches and LAN switches. WAN switches are mainly used in the telecom field to provide basic communication platforms. LAN switches are used in local networks to connect terminal devices, such as PCs and network printers. The transmission media and transmission speed can be divided into Ethernet switches, Fast Ethernet switches, Gigabit Ethernet switches, FDDI switches, ATM switches, and wildcard ring switches.

Large-scale applications can be divided into enterprise-level switches, department-level switches, and working group switches. Generally, enterprise-level switches are rack-mounted and department-level switches can be rack-mounted or fixed-configuration switches, the workgroup-level switch is a fixed configuration (simple function ). On the other hand, from the perspective of application scale, enterprise-level switches support large enterprise applications with more than 500 information points as enterprise-level switches, and department-level switches support Switches of medium enterprises with less than 300 information points, switches that support less than 100 information points are working group-level switches. The vswitch mentioned in this Article refers to a LAN switch.