TCP 3-way-handshake

Question

Comments

is option (2) ???can you provide the answer??

Answer 1

Only S2 is false.

Reason :

TCP client moves from FIN-WAIT-1 -> FIN-WAIT-2 -> TIMED WAIT -> CLOSED.

It goes to timed wait because there is some data might be arriving to the client by the server. So, TCP activates the timeout timer and waits for maximum data roundtrip time and then it goes to CLOSED STATE.

Why S1,S2 is true:

Because whatever happens client sends FIN and goes to FIN-WAIT-1 and if ACK is lost. Server doesn't know it and sends FIN. Now client realizes ACK is lost, (because it receives FIN instead of ACK)  and goes to TIMED WAIT.

TCP server if receives FIN and goes to CLOSE WAIT STATE then it sends FIN and moves to LAST ACK STATE then if ACK is lost from the client (no problem) , eventually it goes to closed after using Keep alive timer.

Comments

They've given S2 and S3 as answer.

Answer 2

only S3 is false….. as S1 is true, and S2 is also true (symmetric connection ending) and in case of S3, if even after RTO the client has not recieved the ACKN, the client moves ahead to END the connection. Thus S3 is False.