The article discusses the control bits, state machine, and three-way handshake of TCP. The control bits in the TCP packet header are explained, including SYN, ACK, FIN, RST, PSH, URG, and ECE. The importance of sequence numbers (Seq) and segment length (Len) in ensuring ordered transmission is highlighted. The TCP state machine diagram is illustrated along with a detailed explanation of the three-way handshake process. The proof of the necessity of at least three handshakes for a reliable TCP connection is provided through mathematical and packet sequence analysis. The article concludes that the three-way handshake ensures basic connection reliability in TCP communication.
https://www.pixelstech.net/article/1727412048-Why-TCP-needs-3-handshakes