What is the purpose of the FCS field in an Ethernet frame?

The Frame Check Sequence (FCS) field in an Ethernet frame is utilized specifically for error detection. When an Ethernet frame is transmitted over a network, it is subject to various forms of interference that may cause data corruption. The FCS field contains a cyclic redundancy check (CRC) value, which is generated from the frame's content at the sender's end. Upon receiving the frame, the recipient calculates the CRC for the received data and compares it to the value in the FCS field.

If the two CRC values match, it indicates that the frame was received without errors; if they don't match, it signifies that the frame has been corrupted during transmission, prompting the receiver to discard the frame or request a retransmission. Thus, the primary purpose of the FCS field is to ensure data integrity during transmission by enabling devices to detect accidental changes to the raw data in the frame.

Other aspects like identifying the sender, determining frame size, or indicating frame type are not functions of the FCS field. Those are handled by other parts of the Ethernet frame, ensuring that the FCS serves its dedicated role in error checking.