Cut-through switching

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In computer networking, cut-through switching is a switching method for packet switching systems, wherein the switch starts forwarding a frame (or packet) before the whole frame has been received, normally as soon as the destination address is processed. This technique reduces latency through the switch, but decreases reliability.

In packet switched networks such as Ethernet, pure cut-through switching can only be used where the speed of the outgoing interface is less than or equal to the incoming interface speed.

The main reason for not adopting cut-through routing is queueing backlog.

Cut through routing was one of the important features of IP networks using ATM networks since the edge routers of the ATM network were able to use cell switching through the core of the network with low latency at all points. With higher speed links, this has become less of a problem since packet latency has become much smaller.

Cut-through switching is very popular in InfiniBand networks, since these are often deployed in environments where latency is a prime concern, such as supercomputer clusters.

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