200-201 Question 286
Single answerAn organization is troubleshooting an issue where a web application running on a server is not receiving any data from clients. Upon investigation, it is found that the TCP three-way handshake is not completing successfully. Which step in the handshake is likely failing if the server receives a SYN packet but does not respond to the client?
- A
The client is not sending the initial SYN packet.
- B
The server is not sending back the SYN-ACK packet.
- C
The client is not sending the final ACK packet.
- D
The TCP sequence numbers are mismatched between the client and server.
Show answer and explanation
Correct answer: B
Explanation
The TCP three-way handshake involves three steps: the client sends a SYN, the server responds with a SYN-ACK, and the client completes the handshake with an ACK. In this scenario, the issue arises after the server receives the initial SYN but does not respond with a SYN-ACK, indicating the failure occurs at the second step of the handshake.
- A. Incorrect.
Incorrect. If the client was not sending the initial SYN packet, the server would not be aware of any connection attempt, and there would be no SYN received by the server.
- B. Correct.
Correct. If the server receives the SYN from the client but does not respond with a SYN-ACK, the handshake cannot proceed, and the connection will fail.
- C. Incorrect.
Incorrect. If the client was not sending the final ACK packet, it would imply that the server had already sent the SYN-ACK successfully. This is not the issue described in the scenario.
- D. Incorrect.
Incorrect. Mismatched sequence numbers could cause issues during data transfer but would not prevent the SYN-ACK response from being sent by the server.