What are the three parts of a TCP handshake?

• A. SYN - SYN/ACK - ACK
• B. SYN, ACK, FIN
• C. ACK, SYN, FIN
• D. SYN, SYN/ACK, FIN

Answer: (A)

TCP connects two hosts by a three-step handshake that sets up a reliable, ordered channel before any data is sent. The client starts by sending a segment with the SYN flag, signaling a request to open a connection and to establish the initial sequence number. The server replies with a segment that has both SYN and ACK flags: it provides its own initial sequence number and acknowledges the client’s SYN. Finally, the client sends a segment with the ACK flag to acknowledge the server’s sequence number, completing the handshake and allowing data transfer to begin. This sequence—SYN, SYN/ACK, ACK—is why that answer is correct.

The other options mix in terms used for ending a connection (FIN) or place flags in an order that doesn’t properly establish the connection. For example, including FIN in the handshake corresponds to termination, not setup, and an order that starts with ACK or places FIN instead of the final ACK would not complete the connection establishment.