The working principle and type differences of vswitches, and the working principle of vswitches

The working principle and type differences of vswitches, and the working principle of vswitches
The emergence of many new Client/Server applications and multimedia technologies has led to the fact that traditional shared networks are far from meeting the requirements, which has promoted the emergence of LAN switches.

1. vswitch Definition

A lan switch has many ports, each of which has its own dedicated bandwidth and can connect to different CIDR blocks. The communication between the ports of the vswitch is parallel, which greatly improves the information throughput. To further improve performance, each port can connect to only one device.

To achieve interconnection between switches or connections with high-end servers, LAN switches generally have one or several high-speed ports, such as 155 M Ethernet port, FDDI port, or m atm port, this ensures the transmission performance of the entire network.

2. vswitch features

Users who share a LAN through a hub not only share bandwidth, but also compete for bandwidth. Some users may need more bandwidth to reduce the available bandwidth of other users, or even be forced to wait, thus delaying communication and information processing. Using the vswitch's network differential segment technology, users of a large shared LAN can be divided into many independent network segments to reduce the number of users competing for bandwidth and increase the available bandwidth for each user, this reduces the congestion of shared networks. Because the switch can quickly and directly send information to the destination, it can greatly increase the speed and bandwidth, protect users' previous investment in media, and provide good scalability, therefore, a switch is not only an ideal alternative to a bridge, but also an ideal alternative to a hub.

Compared with bridges and hubs, vswitches improve the performance in the following aspects:

(1) The information throughput of the switch is improved by supporting parallel communication.

(2) divide users on a traditional large LAN into several working groups. Each port connects to a device or a working group, effectively solving the congestion. This method is called Micro-segmentation technology.

(3) The emergence of the virtualization ai lan technology brings more flexibility to the use and management of switches. We will introduce virtual networks later.

(4) The port density is comparable to that of a hub. Generally, the network system has one or more servers, and most of them are common clients. The client needs to access the server. As a result, the communication and transaction processing capabilities of the server become the key to the overall network performance.

The switch improves the performance of the entire network by increasing the speed of the port connecting to the server and the size of the corresponding frame buffer to meet user requirements. Some high-end switches also adopt full duplex technology to further increase the bandwidth of the port. In the past, network devices basically used half-duplex methods. That is, when a host sends data packets, it cannot receive data packets. When receiving data packets, it cannot send data packets. Because full duplex technology is used, that is, the host can receive data packets while sending data packets, the normal 10 M port can be changed to 20 M port, and the normal 200 M port can be changed to M port, this further improves the information throughput.

3. How the vswitch works

Traditional switches are essentially multi-port bridges with traffic control capabilities, that is, traditional (L2) switches. Introducing the routing technology into a vswitch can complete network-layer routing selection, which is called layer-3 switching. This is a new development of vswitches. The working principle of a switch (L2 Switch) is similar to that of a bridge. A switch is a networking device that works on the Link Layer. Each port of a switch has a bridging function, each port can be connected to a LAN or a high-performance website or server, so that you can learn the connection status of each port through self-learning. All ports are controlled by dedicated processors and forwarded through the control management bus.

At the same time, specialized network management software can be used for centralized management. To improve the speed and efficiency of data exchange, vswitches generally support multiple methods.

(1) Storage forwarding:

All common bridges use this method. Before sending data frame columns to other ports, they need to completely store the received frames in the internal memory, verify the received frames, and then send them to other ports, in this way, the latency is equal to the total time of receiving a complete data frame and the processing time. If the cascade is very long, it will cause serious performance problems, but this method can filter out the wrong data frame.

(2) cut-in method:

This method only checks the target address of the data frame, so that the data frame can be transmitted almost immediately, thus greatly reducing the latency.

The disadvantage is that the error frame will also be transmitted. When the probability of a wrong frame is small, you can use the cut-in method to increase the transmission speed. When the probability of a wrong frame is large, you can use the storage and forwarding method/to reduce the retransmission of the wrong frame.

4. Switch configuration

Next we will take the Cisco Catlystl900 switch as an example to introduce the general configuration process of the switch.

You can use the default configuration of a new Catlystl900 switch. This is because it is a hardware device that installs software in FlashMemory. When powered on, it must first perform a series of self-checks. After testing all ports, the switch will be in the working state. At this time, its switch table is empty. It can learn the connection status of devices on each port through self-learning, and record the MAC address of the device in the switch table. When there is information exchange, the switch forwards data according to the switch table.

To facilitate network management, the Catlystl900 switch has a MAC address, so that it can be assigned an IP address and a shielding code. The network administrator must connect to a terminal or simulation terminal through the serial port of the switch to specify an IP address. The default value is 0.0.0.0. After an IP address is specified, the network administrator can perform remote management over the network. The configuration interface of the Catlystl900 switch is in the menu format. By default, all its ports belong to the same VLAN, and in many cases no modification is required.

(1) connect the serial port of the Microcomputer to the Console port of Cata1yst1900 through the RS 232 cable and run the simulation terminal software after the Catalyst 1900 is started.

(2) Press enter to go to the main menu:

(3) press the "S" key to enter the system configuration menu: (configure the system name, location, date)

(4) Press "N" in the main menu to enter the network management menu.

(5) Configure IP address location

(6) Configure SNMP Parameters

5. vswitch types

A vswitch is a data link layer device that connects multiple physical LAN network segments to a large network. Similar to a network, vswitch transmission and overflow are based on MAC addresses. Because the switch is implemented by hardware, the transmission speed is very fast. When data packets are transmitted, the switch either uses the storage-forwarding and switching mode or the off-switching mode. There are many types of switches, including ATM switches, LAN switches, and different WAN switches.

ATM Switch

The Asynchronous Transfer Mode provides high-speed information exchange and scalable bandwidth capabilities for Working Groups, enterprise network hubs, and many other fields. The ATM switch supports voice, video, and text data applications and can be used to exchange fixed-length information units (sometimes called elements ). An enterprise network is composed of multiple LANs connected through an ATM hub link.

LAN switch

A lan switch is used to connect multiple lan cidr blocks. It performs dedicated non-conflict communication between network devices and supports conversations between multiple devices. LAN switches are mainly used to exchange data frames at high speed. A 0 Mbps Ethernet is interconnected with a 100 Mbps Ethernet through a LAN switch.