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Cut-through switching is a switching method used in packet-switching systems where the switch forwards packets or frames to its destination immediately after the destination address has been processed without waiting for the entire data to be received.
The switch immediately transmits packets it receives and uses CRC checks for error checking and then relies on the destination devices for error handling of the transmitted corrupted data which it has marked. In this case, the switch can be considered as a mere forwarder of data packets and offers low-latency performance as a result.
Cut-through switching offers low-latency performance for SCSI traffic and is used primarily in Fiber Channels. Cut-through switches perform cyclic redundancy checks on incoming packets and marks corrupted frame EOF field as invalid. The destination devices see the invalid flag and drop the frame before it reaches the application. This is a reliable error-handling method which minimizes the time to recover bad frames because the recovery can start immediately compared to the "store and forward" method, which forces a SCSI timeout at the switch where the bad frame is detected. The SCSI retry for recovery would cost another few seconds of waiting.
Cut-through switching is primarily used in Fiber Channel because the reliability of destination-based error handling is mandated by the standards driven by the Technical Committee T11, which imposes Fiber Channel standards.