Which one of the following control fields in TCP header is used to specify…
2015
Which one of the following control fields in TCP header is used to specify whether the sender has no more data to transmit ?
- A.
FIN
- B.
RST
- C.
SYN
- D.
PSH
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Correct answer: A
Answer: FIN
Explanation: The FIN control bit is used to indicate that the sender has finished sending data and wishes to close its side of the TCP connection. This is part of TCP's orderly connection termination.
Typical termination sequence:
1. Endpoint A sends a segment with the FIN bit set to indicate no more data.
2. Endpoint B acknowledges the FIN (ACK).
3. When B has no more data, B sends its own FIN, and A acknowledges it, completing the graceful close.
Quick notes on the other control flags:
RST: Resets or aborts a connection immediately; used for error conditions or when no socket exists for the incoming segment.
SYN: Used to synchronize sequence numbers during connection setup (the three-way handshake).
PSH: Instructs the receiver to pass buffered data to the application promptly; it does not signal connection termination.