GATE CS 2026 Set 1 Q.18: Transport Layer: UDP, TCP Flow and Congestion Control, Sockets

With respect to a TCP connection between a client and a server, which one of the following statements is true?

The client and server use a two-way handshake mechanism before the start of data transmission

The server cannot initiate closing of the connection before the client initiates closing of the connection

The TCP connection is half-duplex

The client and server can initiate closing of the connection at the same time

Official answer and solution

Solution

Review TCP connection establishment (3-way handshake), full-duplex data transfer, and connection termination (including simultaneous close).

Option (A) is false: TCP uses a three-way handshake (SYN, SYN-ACK, ACK) to establish a connection.
Option (B) is false: Either peer (client or server) can independently initiate connection termination by sending a FIN segment.
Option (C) is false: A TCP connection is full-duplex.
Option (D) is true: TCP supports simultaneous close, where both client and server send FIN segments concurrently and transition through FIN_WAIT_1 $\rightarrow$ CLOSING $\rightarrow$ TIME_WAIT.

Final answer

Option (D)

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Paper: GATE 2026 Computer Science and Information Technology - Session 1 (CS1)
Question: 18 of 65
Section: Computer Science and Information Technology

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