I read that TCP is in layer 4. But i also read that to send data with TCP i have to establish a session (in the handshaking phase). Does this mean that if we work only up to layer 4 TCP is useless (since i cannot establish sessions) ?

  • The session management is part of TCP. – JFL Dec 12 '19 at 13:12
  • The OSI model is just a model, and nothing in the real world follows it (OSes have never implemented separate layers 5, 6, and 7, lumping all of them into the Application layer). The IP Services model is much closer to what really happens, but even that is just a model. – Ron Maupin Dec 12 '19 at 14:10

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