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There are three modes of switch forwarding

  1. Cut Through

A straight-through Ethernet switch can be understood as a matrix telephone switch that criss-crosses ports. When it detects a packet in the input port, it checks the packet header, obtains the destination address of the packet, starts the internal dynamic lookup table and converts it into the corresponding output port, connects at the intersection of input and output, and passes the packet through to the corresponding port to realize the switching function. Since no storage is required, the latency is very small and the exchange is very fast, which are its advantages. The disadvantage is that the packet content is not saved by the Ethernet switch, so it cannot check whether the packet is incorrect and does not provide error detection capability. Because there is no cache, input/output ports with different rates cannot be connected directly, and packet loss is easy.

  1. Store and Forward (Store & Forward)

Storage and forwarding is the most widely used method in computer network. It checks the data packet of the input port, takes out the destination address of the data packet after processing the error packet, and converts it into the output port to send the packet through the lookup table. Because of this, the store-and-forward method has a large delay in data processing, which is its shortcoming. However, it can detect the error of packets entering the switch and effectively improve the network performance. In particular, it can support the conversion between ports of different speeds and keep the cooperation between high-speed ports and low-speed ports.

  1. Fragment Free

This is a solution somewhere in between. It checks whether the packet length is 64 bytes. If the packet length is less than 64 bytes, the packet is fake and discarded. If larger than 64 bytes, the packet is sent. This method also does not provide data verification. Its data processing speed is faster than store-and-forward mode, but slower than straight-through mode.



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