You're troubleshooting a connection issue between two hosts. Packets are being sent by client A to server B on port 80, but no response is received. After analyzing the network capture, you notice only SYN packets from client A are present. What's the most likely explanation?1.0 MarksServer B's firewall is blocking incoming connections on port 80.Client A's TCP sequence number is incorrect, causing server B to reject the connection.Server B is offline or experiencing hardware failure.Client A's application forgot to send the ACK packet in the handshake sequence.The 3-way handshake is incomplete due to packet loss or network congestion.
Question
You're troubleshooting a connection issue between two hosts. Packets are being sent by client A to server B on port 80, but no response is received. After analyzing the network capture, you notice only SYN packets from client A are present. What's the most likely explanation?1.0 MarksServer B's firewall is blocking incoming connections on port 80.Client A's TCP sequence number is incorrect, causing server B to reject the connection.Server B is offline or experiencing hardware failure.Client A's application forgot to send the ACK packet in the handshake sequence.The 3-way handshake is incomplete due to packet loss or network congestion.
Solution
The most likely explanation for this scenario is that Server B's firewall is blocking incoming connections on port 80.
Here's why:
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In a typical TCP/IP network communication, a three-way handshake is initiated by the client (in this case, client A). The client sends a SYN packet to the server (server B) to initiate the connection.
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If the server receives the SYN packet and is ready to establish the connection, it should respond with a SYN-ACK packet.
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However, in this scenario, you're only seeing SYN packets from client A and no response from server B. This suggests that server B is not receiving the SYN packets or is unable to respond.
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If server B's firewall is configured to block incoming connections on port 80, it would prevent the server from receiving the SYN packets from client A, hence no SYN-ACK packets are sent back to client A.
The other options are less likely because:
- An incorrect TCP sequence number from client A would typically result in a reset (RST) packet from server B, not silence.
- If server B was offline or experiencing hardware failure, you would likely see other signs of this, and it wouldn't specifically result in the absence of SYN-ACK packets.
- The client's application forgetting to send the ACK packet would occur later in the handshake process, after the server has sent a SYN-ACK packet.
- An incomplete 3-way handshake due to packet loss or network congestion would typically result in retransmissions of the SYN packet from client A, which doesn't seem to be the case here.
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