Vswitch basic knowledge Summary: Past and Present

Switch "past life"-Technology Development History

Origin

"Switch" is the term "Switch". It is derived from the English word "Switch", which is originally intended to be "Switch". When China's technical community introduces this word, it is translated as "Exchange ". In English, the verb "Exchange" and the term "Switch" are the same word. Note that the "Exchange" here refers to the signal exchange in telecommunications technology, which is not the same as the exchange of goods ).

In 1993, LAN switching equipment emerged. In 1994, the exchange network technology boom began in China. In fact, the exchange technology is a simplified, low-cost, high-performance, and high-port intensive exchange product, reflecting the second-layer operations of the complex exchange technology in the OSI reference model. AndBridgeIn the same way, the switch simply decides to forward information based on the MAC address in each package. This type of forwarding decision generally does not consider the deeper information hidden in the package. The difference with the bridge adapter is that the forwarding delay of the switch is very small, and the operation is similar to the performance of a single LAN, far exceeding the forwarding performance between common Bridging networks.

The exchange technology allows the shared and dedicated LAN segments to adjust the bandwidth to reduce the bottleneck of information flow between the LAN. Now there are Ethernet, fast Ethernet, FDDI and ATM exchange products.

Similar to traditional bridges, vswitches provide many network interconnection functions. Vswitches can economically divide networks into small conflicting domains to provide higher bandwidth for each workstation. Protocol transparency allows the switch to be directly installed in a multi-protocol network with simple software configuration. The switch uses the NIC of the existing cable, repeater, hub, and workstation, you do not need to perform high-level hardware upgrades. vswitches are transparent to workstations. This reduces management costs and simplifies the operations of adding, moving, and changing network nodes.

Using a specially designed integrated circuit, the switch can forward information on all ports at a line rate in parallel, providing much higher operation performance than the traditional bridge. For example, theoretically, a single Ethernet port can provide a transmission rate of 14880bps for data packets containing 64 octal packets. This means that a "line rate" Ethernet switch with 12 ports that support six parallel data streams must provide a total throughput of BPS and six information flows (X14880bps/information flows ). The dedicated integrated circuit technology enables the switch to achieve the above performance with more ports. The port cost is lower than that of the traditional bridge.

Manual exchange

The electrical signal exchange history should be traced back to the early stages of the telephone appearance. After the phone was invented, only a long enough wire, coupled with two end calls, can make the two people far apart voice conversation.

When the number of phones increases, it is impossible for us to draw a line between every two phones to make everyone with the phone communicate with each other. As a result, people set up a telephone board. Every telephone user connects a line to a large circuit board of the telephone board. When A wants to talk to B, he requests the telephone department's operator to connect B. The operator uses A wire to insert one end into the hole A receives from the circuit board and the other end into the hole B. This is "connection", which is equivalent to temporarily pulling A telephone line for A and B, now both parties can talk. After the call is completed, the operator disconnects the wire ". The entire process is "manual switching", which is actually a process of "Closing the switch" and "disconnecting the switch. Therefore, it is technically easier to translate "switch" into "switch.

Programmable Circuit Switch

The efficiency of manual exchange is too low to meet the needs of large-scale telephone deployment. With the development of semiconductor technology and the maturity of switching circuit technology, it is found that electronic technology can be used to replace manual exchange. As long as a telephone end user sends an electrical signal to an electronic device, the electronic device can connect the circuit of the requester and the requested party according to the preset procedure and exclusively occupy the circuit, it will not be shared with a third party. Of course, due to design defects, the circuit may be shared by many people, which is also known as the "string line "). This exchange method is called "program-controlled exchange ". This kind of device is the "Programmable switch ".

Because the program-controlled exchange technology has been monopolized by developed countries for a long time and the equipment is expensive, China's telephone penetration rate has not been high. As companies such as Huawei and ZTE developed their own program-controlled switches in the past, telephones were rapidly popularized in China. Currently, the communication protocol commonly used by voice program-controlled switches is Signalling System No. 7)

Ethernet Switch

With the rapid development of computers and their interconnection technologies, also known as "Network Technology", Ethernet has become the second-layer computer network with the highest penetration rate so far. The core component of Ethernet is the Ethernet switch. Both manual switching and program-controlled switching are designed to transmit voice signals, and they are "Circuit switches" that require exclusive lines ". However, Ethernet is a computer network and data needs to be transmitted. Therefore, "group switching" is used ". However, no matter which type of switch is used, the "exclusive Channel" feature provided by the switch for two points will not change.

For Ethernet devices, the essential difference between A switch and A hub is that when A sends A message to B, all the network nodes connected to the hub will receive this message, which is also sent in the form of broadcast), but the NIC will filter out the information not sent to the local machine at the hardware level, unless A notifies the switch to broadcast, the information sent to B C will never receive the switch control permission and listen ).

At present, Ethernet switch manufacturers have launched three-layer or even four-layer switches based on market demands. However, in any case, its core function is still layer-2 Ethernet packet exchange, but with a certain degree of ability to process IP layer or even higher layer data packets.

Optical Switching

Light exchange is the next generation exchange technology that people are developing. Currently, all switching technologies are based on electrical signals. Even the current optical fiber switch converts optical signals into electrical signals. After switching, the optical signals are sent back to another optical fiber. Because the photoelectric conversion rate is low and the processing speed of the circuit has a physical bottleneck, we hope to design an "Optical Switch" that does not require photoelectric conversion ", it is not a circuit but a optical path. The original logic is not a switching circuit but a switching optical path. This will greatly increase the processing speed of the vswitch.

Switch "This life"-development prospects

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 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 switch can play a role. Because the purpose of using a vswitch is to minimize and filter data traffic in the network, if a vswitch 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 a vswitch because of the processing time of data packets, the buffer size of the vswitch, 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.

The development of switch equipment is rapid, because the development of the network can not be slow, the configuration and performance of the switch affects the connection between the network, so please pay more attention to the status of the switch, the update frequency is very high.