Describe the TCP three-way handshake and its purpose.

• A. SYN, SYN-ACK, ACK; establishes a reliable connection and negotiates sequencing.
• B. ACK, FIN, RST.
• C. SYN, ACK, FIN.
• D. GET, POST, ACK.

Answer: (A)

The key idea is that TCP uses a handshake to set up a reliable, ordered connection before any data is sent. The client starts by sending a segment with the SYN flag to request a connection and to pick an initial sequence number. The server replies with a segment that has both the SYN and ACK flags, acknowledging the client’s SYN and providing its own initial sequence number. The client then sends a final segment with the ACK flag to confirm the server’s sequence number. Once this exchange finishes, both sides know they can trust the path, track byte order with sequence numbers, and establish the parameters needed for reliable data transfer. After the handshake, data can flow in both directions with the connection being managed for reliability and proper sequencing. The other options don’t fit because they involve closing, resetting, or higher-level HTTP actions rather than starting a TCP connection.