TCP Handshake

Abstract

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• A 3-way handshake which includes 4 events to start a TCP Connection

4 events

1. A -> B: A sends a SYN packet to B, with its Initial Sequence Number (ISN) set to x. The Acknowledgement Number is set to all zeros.
2. A <- B: B ACK and informs A that it is ready for x+1, indicating that it has received A’s SYN packet.
3. A <- B: Since TCP is bidirectional, B also sends its own SYN packet to A, with its ISN set to y.
4. A -> B: A ACK and informs B that it is ready for y+1, confirming that it has received B’s SYN packet.

For events two and three, both occur from B to A, and the fields used in the TCP packet do not overlap. This means both events happen in the same packet. This is why the 3-way handshake consists of 4 events.