What is the role of acknowledgments in TCP?

• A. To confirm that data has been successfully received.
• B. To encrypt data in transit.
• C. To set the MTU value.
• D. To initiate a connection.

Answer: (A)

In TCP, acknowledgments are used to confirm that the data sent has arrived, enabling reliable, in-order delivery. Each received segment prompts an ACK that carries the next expected sequence number, letting the sender know exactly up to which byte has been successfully received and, via the window information, how much more data the receiver can accept. If an ACK is not received in time, the sender will retransmit, providing reliability. Acknowledgments also support estimating round-trip time for congestion control and can be piggybacked on data to reduce overhead. They do not encrypt data, do not set the MTU, and do not initiate the connection.