For those of you who do not understand the above conversation, I suggest reading the resource linked above as sent by @user207421

Surely you already have relevant texts to study? If you don't, you should read RFC 793 or W.R. Stevens, TCP/IP Illustrated, volume I, relevant chapters. You have several major misunderstandings here.

RFC 793 Page 4 and Page 5 of the introduction seem to be enough for understanding the core discussion above!