What is the role of the Frame Check Sequence (FCS) in an Ethernet frame?

The Frame Check Sequence (FCS) plays a critical role in maintaining data integrity in an Ethernet frame. It is a sequence of bits added to the end of the frame that is used for error detection. When a frame is transmitted over the network, the sending device calculates a checksum based on the contents of the frame and appends this checksum, known as the FCS, to the frame.

When the receiving device gets the frame, it performs a similar calculation on the received data and compares the result with the FCS value. If the two values match, it indicates that the frame was received without errors. Conversely, if there is a mismatch, it suggests that the frame may have been corrupted during transmission due to noise, interference, or other factors, prompting the receiving device to discard the faulty frame and request a retransmission if necessary.

This error detection mechanism is essential for ensuring reliable communication over Ethernet networks, as it helps maintain the integrity of the data being transmitted. Without FCS, there would be no straightforward method to determine whether the data has been altered or corrupted during transit.