In TCP, an ACK number of 1000 always means that ______.
2015
In TCP, an ACK number of 1000 always means that ______.
- A.
999 bytes have been successfully received
- B.
1000 bytes have been successfully received
- C.
1001 bytes have been successfully received
- D.
None of the above
Attempted by 167 students.
Show answer & explanation
Correct answer: D
Correct answer: None of the above
TCP acknowledgement numbers are cumulative: the ACK number tells the next sequence number the receiver expects.
So ACK = 1000 means the receiver expects sequence number 1000 next, and bytes with smaller sequence numbers in that TCP sequence space have been received.
However, TCP sequence numbering starts from an Initial Sequence Number (ISN), not necessarily from 0 or 1. Therefore ACK = 1000 does not always mean exactly 999, 1000, or 1001 data bytes were received.
A video solution is available for this question — log in and enroll to watch it.