In a network packet capture, what do the Sequence (Seq) and Acknowledgment (Ack) fields primarily indicate?

• A. The time-to-live and identification values
• B. The destination port and source port
• C. The window size
• D. The sequence of bytes in the TCP stream and acknowledgment of bytes received

Answer: (D)

TCP uses sequencing and acknowledgments to ensure reliable, ordered delivery of data. The Sequence value marks the position of the first byte of data in this segment within the overall byte stream from the sender. The Acknowledgment value indicates the next byte the sender of this segment expects to receive from the peer, effectively acknowledging all bytes up to that point. Together, they let both ends know what data has been received, what remains to be sent, and when retransmissions are needed to recover missing information. The window size is a separate flow-control field that tells the peer how much more data it can send before waiting, but it does not define the position or acknowledgment of data.