Connection Establishment & Release

Computer Network & Network Security System — Transport Layer, NEC licence examination syllabus (Nepal Engineering Council).

Connection Establishment & Release: TCP's famous handshake

Every time you open a website, this exact three-step dance happens first, invisibly, in milliseconds.

🤝 The Three-Way Handshake

Step 1 — SYNClient sends a SYN segment with an initial sequence number, requesting a connection.

Step 2 — SYN-ACKServer acknowledges and sends its own SYN back.

Step 3 — ACKClient acknowledges the server's SYN. Connection is now fully established.

Connection termination typically uses a four-step process (sometimes called a "four-way handshake") — each side independently sends a FIN and receives an ACK, since a TCP connection is really two independent one-way streams that must each be closed.

💡 Draw the three-way handshake diagram with correct SYN/SYN-ACK/ACK labels and sequence number notation exactly as shown — this exact diagram is asked almost every year.

Syllabus points

TCP three-way handshake
Connection termination

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