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GATE 2025 CS (CS1) – Question 22

Computer Networks · TCP: Flow Control, Congestion Control, Socket API · 1 mark · Multiple select

Consider the 3-way handshaking protocol for TCP connection establishment. Let the three packets exchanged during the connection establishment be denoted as P1, P2, and P3, in order. Which of the following option(s) is/are TRUE with respect to TCP header flags that are set in the packets?

  1. P3: SYN = 1, ACK = 1
  2. P2: SYN = 1, ACK = 1
  3. P2: SYN = 0, ACK = 1
  4. P1: SYN = 1

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Show answer and explanation

Correct answer: (B) P2: SYN = 1, ACK = 1; (D) P1: SYN = 1

Explanation

P1 is SYN (SYN=1), P2 is SYN+ACK (SYN=1, ACK=1), and P3 is ACK (SYN=0, ACK=1).