Application Guide: Ethernet switch full solution

Currently, the longest way to use an Ethernet switch is through-through. A through-through Ethernet switch can be understood as a line matrix telephone switch 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 port number of the Ethernet switch increases, 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 packets entering the Ethernet 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.

It has the routing function of multi-channel broadcast and virtual network based on IP, IPX and other protocols. the smooth implementation of this function is due to the addition of dedicated ic asic, the traditional instruction from software processing is changed to the embedded instruction of ASIC chip, thus accelerating packet forwarding and filtering, this ensures 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 an Ethernet switch to build a virtual network is to divide the logic of all the ports of the original Ethernet switch in a large broadcast area 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.