TCP client P successfully establishes a connection to TCP server Q. Let…
2024
TCP client P successfully establishes a connection to TCP server Q. Let \(N_P\) denote the sequence number in the SYN sent from P to Q. Let \(N_Q\) denote the acknowledgement number in the SYN ACK from Q to P. Which of the following statements is/are CORRECT?
- A.
The sequence number
\(N_P\)is chosen randomly by P - B.
The sequence number
\(N_P\)is always 0 for a new connection - C.
The acknowledgement number
\(N_Q\)is equal to\(N_P\) - D.
The acknowledgement number
\(N_Q\)is equal to\(N_P\)+ 1
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Correct answer: A, D
Key idea: TCP picks an initial sequence number for each side and a SYN consumes one sequence number.
Initial sequence number is chosen randomly by the client (ISN). This prevents old-packet confusion and improves security.
The server's acknowledgement in the SYN-ACK equals the client's ISN + 1 because the SYN consumes one sequence number. Example: if N_P = 1000, then N_Q = 1001.
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