What is the role of the footer in the message frame?

• A. The footer contains integrity information such as checksum/CRC.
• B. The footer stores the sender's identity.
• C. Footer is used to compress data.
• D. Footer holds encryption keys.

Answer: (A)

The footer’s role is to provide integrity verification for the frame. It typically contains an error-detection code such as a checksum or CRC that was computed over the payload (and sometimes the header) before transmission. When the frame arrives, the receiver recalculates the same code on the received data and compares it to the value in the footer. If they match, the data integrity is confirmed; if not, the frame is considered corrupted and is usually discarded or flagged for retransmission.

This concept explains why the footer is the best answer: it directly serves to detect errors in transit. It’s not primarily about identifying the sender, reducing size through compression, or distributing encryption keys—the footer is dedicated to ensuring the data hasn’t been altered during transmission.