Exchange Technology Development Process -- exchange Ethernet Technology

Exchange Technology Development Process

Ethernet SWITCH, which is also translated as a SWITCH or a SWITCH-type hub. Let's first review the development process of LAN.

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, due to the sharp increase in traffic, the development of technology led to the increasing performance of the LAN. The earliest 1 Mbps speed was widely replaced by today's 100BASE-T and 100CG-ANYLAN, traditional media access methods are limited to making a large number of sites share access to a public transmission media, both CSMA and CD.

In the early 1990s s, with the improvement of computer performance and the increasing traffic, traditional local area networks have already surpassed their own load. Switched Ethernet technology emerged, greatly improving the performance of local area networks. 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 can transmit information in parallel, securely, and simultaneously, and make the LAN highly scalable.

From Bridge, multi-port bridge to switch

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.

Ethernet Switching Technology (SWITCH) is developed on the basis of multi-port bridges in the early 1990s S. The two-layer protocols for implementing the OSI model are closely related to the bridges, 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 can provide more ports 4 ~ 88), better performance, stronger management functions, and cheaper prices. Some LAN switches have also implemented the layer-3 protocol of the OSI reference model to achieve simple routing selection. Currently, layer-3 switching is very popular. Similar to a telephone switch, an Ethernet switch provides other bridging technologies, such as cut through, in addition to store ang forword ).

Working principle of switched Ethernet

The principle of the Ethernet switch is very simple. It detects the Source and Destination MAC media access layer addresses of packets from the Ethernet port, and then compares them with the dynamic search table in the system, if the MAC address of the data packet is not in the query table, add the address to the query table and send the data packet to the target port.

Advantages of switched Ethernet Technology

For switched Ethernet, you do not need to change other network hardware, including cables and user NICs. Instead, you only need to change the shared HUB with a switched switch to save your network upgrade costs.

You can switch between high-speed and low-speed networks to achieve collaboration between different networks. Currently, most switched Ethernet networks have Mbps ports. The corresponding Mbps Nic is used to connect to the server. This solves the bottleneck of 10 Mbps and becomes the preferred solution for LAN upgrade.

It provides multiple channels at the same time, providing more bandwidth than the traditional shared hub. The traditional shared 10 MBPS/100MPS Ethernet adopts the broadcast communication mode, and can only communicate with one user at a time, in case of a collision, you have to try again, while the switched Ethernet allows transmission between different users. For example, a 16-port ethernet switch allows 16 sites to communicate between eight links. Particularly in terms of time response, LAN switches are favored. It provides a higher bandwidth and a higher speed than the router at a lower cost than the router, unless there is a WAN) requirement, the switch has a tendency to replace the router.

Directly cut throuth), store the comparison of store-and-forward)

A pass-through Ethernet switch can be understood as a line matrix telephone switch that is crossly And crossly between ports. When a packet is detected on the input port, it checks the packet header, obtains the destination address of the packet, and starts the internal dynamic search table to convert it to the corresponding output port, connect data packets at the intersection of input and output to the corresponding port to implement the switching function. Because there is no need for storage, LATENCY) is very small, exchange is very fast, this is its advantage; its disadvantage is: because the content of the packet is not saved by the Ethernet switch, therefore, it is impossible to check whether the transmitted data packet is incorrect and the error detection capability is not available. Because there is no cache, it is not possible to directly connect the input/output ports with different rates, when the ports of an Ethernet switch increase, the switching matrix becomes more and more complex and implementation is quite difficult.

The storage and forwarding method is the most widely used in the computer network field. It stores input port data packets and performs CRC checks, the destination address of the data packet is extracted after the error packet is processed. The destination address is converted to the output port through the search table. Because of this, the storage and forwarding method is insufficient when the data processing latency is large. It can only detect errors of data packets entering the switch, in particular, it supports conversion between input and output ports at different speeds to ensure the collaboration between high-speed ports and low-speed ports.

Layer 2 and Layer 3 switching and competition with router Solutions

As mentioned above, LAN switches work on the OSI Layer 2 and can be understood as a multi-port bridge. Therefore, they are traditionally called Layer 2 switches. Currently, the switching technology has extended some of OSI's third-layer functions, namely layer-3 switching. layer-3 switching can directly communicate without spreading broadcast packets by using dynamic MAC addresses, it seems that you can understand layer-3 information, such as IP addresses and ARP, and have routing functions based on IP, IPX, and other protocols between multi-channel broadcast and virtual networks, the smooth implementation of this function is due to the addition of specialized ic asic, and the traditional instruction from software processing is changed to the embedded instruction of ASIC chip, this accelerates packet forwarding and filtering, ensuring high-speed linear routing and service quality. Currently, if you do not need a wide area network, you will no longer use vrouters that are expensive and have limited bandwidth in the network creation solution.

Virtual LAN technology

The development of exchange technology allows geographically dispersed organizations to logically become a new working group, and members of the same working group can change their physical addresses without reconfiguration of nodes, this is the so-called virtual LAN technology VLAN ). Using a vswitch to build a virtual network is to make all the ports of the original large broadcast area switch) logic is divided into several "subbroadcast areas ", the broadcast packets in the subbroadcast area are only transmitted in the broadcast area, but cannot be received in other broadcast areas. VLAN uses the exchange technology to effectively separate the traffic, so as to better utilize the bandwidth, and logically split the actual LAN infrastructure into multiple subnets, it allows various local networks to run different application protocols and topologies. For more information, see the rules.

1. Ethernet Switching Technology Trend
2. Ethernet Switch Technology Development Trend