Which statement best describes the TCP three-way handshake?

• A. It uses a single SYN packet to establish a connection
• B. It completes to establish a connection using SYN, SYN/ACK, and ACK
• C. It terminates a connection with FIN
• D. It is used only for UDP connections

Answer: (B)

TCP connection establishment relies on a three-step exchange to set up a reliable stream. The client starts by sending a SYN packet to initiate the connection and to propose its initial sequence number. The server replies with a SYN-ACK, acknowledging the request and providing its own initial sequence number. The client then sends a final ACK to confirm and complete the handshake. Once this exchange finishes, both sides have synchronized sequence numbers and the connection is established, allowing reliable, in-order data transfer to begin.

The other descriptions don’t fit because a single SYN doesn’t complete the necessary mutual synchronization, and the connection wouldn’t be established. Terminating a connection with FIN is about closing, not opening, a connection. UDP is connectionless and does not use a handshake.