What is the only field found in an Ethernet trailer?

The Field Check Sequence (FCS) is critical for ensuring data integrity in Ethernet frames. Located at the end of an Ethernet frame, the FCS is a 32-bit cyclic redundancy check (CRC) value that allows the receiving device to verify whether the frame has been transmitted without errors. When a frame is received, the receiving device calculates the CRC based on the received frame's content and then compares it with the FCS. If the values do not match, the frame is considered corrupt and is typically discarded, prompting a retransmission if necessary.

In contrast, the other fields mentioned serve different purposes within the Ethernet frame structure. The Source Address and Destination Address fields are part of the Ethernet header, providing information about the origin and destination of the data. The Type/Length field is also found in the header and indicates either the type of protocol encapsulated in the payload or the length of the data being transmitted. Hence, the FCS is the only field specifically located in the trailer, highlighting its unique role in frame integrity verification.