Overview of LAN switches and switched Ethernet Technology

Ethernet switches are still commonly used. So I have studied a comprehensive description of LAN switches and switched Ethernet technologies. I would like to share with you here and hope they will be useful to you. 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.

The ethernet SWITCH technology was developed on the basis of a multi-port bridge in the early 1990s s. 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 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 MAC (media access layer) addresses of the Source and Destination 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 requirement for a wide area network (WAN), the switch has a tendency to replace the router.

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 it does not need to be stored, LATENCY is very small, and switching is very fast, this is its advantage; its disadvantage is that the content of data packets 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.