What is CYCLIC REDUNDANCY CHECK (CRC)

CYCLIC REDUNDANCY CHECK (CRC)

The cyclic redundancy check (CRC) is a technique used to detect errors in digital data. CRC is a hash function that detects accidental changes to raw computer data commonly used in digital telecommunications networks and storage devices such as hard disk drives. It is one of the better techniques in detecting common transmission errors.

It is based on binary division and is also called polynomial code checksum.

Frame check sequence (FCS)

Frame check sequence (FCS) refers to the extra bits and characters added to data packets for error detection and control.

Network data is transmitted in frames. Each frame is comprised of bits of data appended to the header, which holds basic information such as source and destination media access control (MAC) addresses and application. Another set of characters is added to the end of the frames, which are checked at the destination. Matching FCSs indicate that delivered data is correct.

Frame check sequence (FCS)

A frame check sequence (FCS) refers to the extra error-detecting code added to a frame in a communications protocol. Frames are used to send upper-layer data and ultimately the application data from a source to a destination.

Note that detection does not also mean error recovery. Ethernet defines that the errored frame should be discarded, but Ethernet takes no action to cause the frame to be retransmitted. Other protocols, notably TCP, can notice the lost data and cause error recovery to occur.