Review and Prospect of switch Product Development

There are many things worth learning about vswitch products. Here we will mainly introduce the Review and Prospect of the Development of vswitch products. The combination of computer technology and communication technology has promoted the rapid development of local computer networks. From the appearance of ALOHA at the end of to the appearance of Mbps switched Ethernet in the middle, in just over thirty years, it has taken a leap from work order to duplex, from sharing to exchange, from low speed to high speed, from simple to complex, from expensive to popular.

In the middle and late 1980s S, the rapid increase in traffic prompted the development of technology, so that the performance of the LAN is getting higher and higher. The earliest 1 Mbps speed has been widely replaced by today's 100Base-TX, however, traditional media access methods are limited to making a large number of sites share access to a public transmission media, that is, CSMA/CD. In the early 1990s s, with the improvement of computer performance and the increase in traffic, the traditional LAN had already exceeded its own load. Switching Ethernet technology emerged, greatly improving the LAN performance. Compared with the network topology of the shared media based on bridges and routers, network switches can significantly increase the bandwidth. With the addition of the exchange technology, you can establish a geographically dispersed network, so that each port of the LAN switch product can transmit information in parallel, securely, and simultaneously, and the LAN can be highly expanded.

The development of LAN switching technology goes back to two port bridges. A bridge is a storage and forwarding device used to connect to a similar LAN. From the perspective of the structure of the interconnected network, the bridge is an end-to-end connection at the DCE level; from the protocol level, the bridge stores and forwards data frames at the logical link layer; similar to the functions of a repeater on the first layer and a router on the third layer. Two-port bridges are developed almost simultaneously with Ethernet.

The ethernet Switch technology was developed in early 1990s on the basis of a multi-port bridge. The two-layer protocol for implementing the OSI model is closely related to the bridge, even known by industry insiders as "many associated bridges", the current exchange technology is not a new standard, but a new application of existing technologies, it is an improved LAN bridge. Compared with traditional bridges, it provides more ports, better performance, stronger management functions, and cheaper prices. Some LAN switch products have also implemented the layer-3 protocol of the OSI reference model to achieve simple routing selection. Currently, layer-3 switching is very popular. Most Ethernet switches provide storage Forwarding (Store and Forward.

Differences between a vswitch and a hub

HUB) is a broadcast mode device, that is, when a port of the HUB is working, all other ports can receive information, which is prone to broadcast storms. When the network size is large, the network performance will be seriously affected. The switch can avoid this phenomenon. When the switch is working, only the requested port and the destination port respond to each other without affecting other ports, that is, the point-to-point mode ). Therefore, vswitches can isolate conflicting domains and effectively suppress broadcast storms.

From the bandwidth perspective, no matter how many ports the hub has, all ports share a bandwidth. At the same time, only two ports can be used to transmit data, while other ports can only wait, at the same time, the hub can only work in half duplex mode. For a vswitch, each port has an exclusive bandwidth. When the two ports work, the operation of other ports is not affected, at the same time, the switch can not only work in half duplex mode, but also in full duplex mode.

Uplink Port

In the past, the Uplink port was a common port on a vswitch to facilitate cascade between two vswitches. It uses the same channel as its adjacent common UTP port. Therefore, if the Uplink port is used, another common port adjacent to it cannot be used. These two ports are called shared ports and cannot be used at the same time. When cascade, you can use the standard that follows the same standard for both ends of the normal main cable, that is, the same as the EIA/TIA 568A or 568B standard) connect the common port of a vswitch to the Uplink port of another vswitch. If both devices are connected using Uplink ports, the cables must use the reversed line (that is, one end uses the EIA/TIA 568A standard, and the other end uses the EIA/TIA 568B standard ). Currently, many vswitches support the automatic port flip function. All ports can be used as Uplink ports or common ports, and can be connected using both the positive line and the reverse line. In this way, there is no dedicated port for Uplink.

Cascade and stack

Stack and Uplink are two ways to connect multiple switches or hubs. Their main purpose is to increase the port density. However, their implementation methods are different. In short, cascade can be completed between switches, between hubs, or between switches and hubs of any network equipment manufacturer through a twisted pair. Stack is only available between devices of your own manufacturer, and the device must have a stack function. Cascade a single twisted pair (or other media) requires dedicated stacking modules and cables, and these devices may need to be purchased separately. In theory, there is no limit on the number of cascade switches (Note: The number of cascade switches is limited, and the requirements for 10 M and M are different ), the devices of each stack manufacturer indicate the maximum number of stacks.

It is easy to perform cascade, But Stack technology has the advantages that cascade cannot achieve. First, multiple vswitches are stacked together. Logically, they belong to the same device. In this way, if you want to set these switches, you only need to connect to any device and you can see other switches in the stack. Cascade devices are logically independent. To manage these devices, they must be connected to each device in sequence.

Second, multiple device-level associations cause cascade bottlenecks. For example, if two 10-Gigabit switches use a twisted pair cascade, their cascade bandwidth is Mbps. In this way, computers of different vswitches can only communicate with each other through the mbps bandwidth. The two switches are connected together through stacks, And the stacked cables can provide a bandwidth higher than 1g, greatly reducing the bottleneck. However, the current switch has a new technology-Port Trunk Port binding). With this technology, you can use multiple twisted pair wires to cascade two switches to increase the cascade bandwidth. In addition, many switches now have Gigabit scalability, And the Gigabit cascade performance is good. As long as there are not too many cascade layers, the uplink speed will not be affected.

Cascading also fails to reach a stack to increase the connection distance. For example, if a computer is far away from a vswitch and exceeds the maximum distance of 100 meters from a single twisted pair wire, a switch can be placed in the middle to connect the computer to the vswitch. The stacking cable is only a few meters at most, so you should consider the stacking. Stack and cascade have their own advantages. They often appear in the actual solution design and can be used flexibly.

Cable Type

The most commonly used twisted pair wires in Ethernet networks include Category 3 wires, Category 5 wires, and Category 5 wires. Currently, Category 5 wires are more than Category 6 wires. The 3rd class line is commonly used for 10 Mbps Ethernet data and voice transmission in the LAN, and complies with the IEEE 10Base-T standard. 5th twisted pair wires currently have the largest LAN market, with a maximum rate of 100 Mbps, in line with the IEEE 3u 100Base-TX standard.

The main difference between Category 5 and Category 5 is the application. Only two pairs of cables are used for transmission during use of Category 5 cables. Category 5 uses four pairs of full duplex transmission to meet Gigabit Ethernet applications. Category 5 has higher performance requirements than Category 5. The difference between cat6 and cat5 lines is that their bandwidth is different. cat5 lines only have 100 MHz, while cat6 lines have 250 MHz. They also support different applications because of different performance. Category 6 lines support more advanced applications. In terms of performance, Category 6 also has higher requirements than Category 5. Generally, the length of the network cable cannot exceed 100 meters.

Rack mounting

Many Ethernet switch products are designed according to EIAElectronic Industrial Association) Electronic Industry Association's standard 19 inch-inch bracket. When installing the rack, first close the connected devices for installation, install the L-type bracket on either side of the front panel of the switch), and fix 1 with screws. Then, use screws to fix the switch on the bracket 2 where the switch is placed ).