How can a transport protocol provide data integrity without guaranteeing delivery?

• A. Providing checksums to detect corruption
• B. Guaranteeing delivery for some streams
• C. Encrypting payload for integrity
• D. Using acknowledgments only

Answer: (A)

Detecting corruption while not guaranteeing delivery hinges on a simple, effective technique: checksums. By attaching a checksum to each segment, the sender provides a fingerprint of the data. When the receiver gets the segment, it recalculates the checksum over the received payload and compares it to the transmitted value. If they match, the data is assumed intact; if they don’t, the corrupted segment is discarded or flagged for retransmission by higher layers. This lets the protocol ensure data integrity—you can trust that what you accept is unchanged—without promising that every piece of data will be delivered.

The other ideas mix in delivery guarantees or rely on encryption concepts that don’t directly address integrity in the same transport-layer sense. Delivering data reliably is about ensuring segments reach the destination, not about detecting corruption; encryption is about confidentiality (and can include integrity in some schemes, but that isn’t the standard, primary mechanism for transport-layer integrity). Relying on acknowledgments alone also centers on delivery, not on detecting and discarding corrupted data.