> Engineers working on TCP decided that a 3-way exchange of messages (3-way handshake) could be used at the beginning of a connection. This is what is currently taught in all of the textbooks. However, in 1978 Richard Watson made a startling discovery: the message exchange was not what achieved the synchronization. It was explicitly bounding three timers. The messages are basically irrelevant to the problem.

This: https://www.rfc-editor.org/ien/ien193.pdf