GATE CSE 2017 Set 1 | Question: 14

Question

Consider a TCP client and a TCP server running on two different machines. After completing data transfer, the TCP client calls close to terminate the connection and a FIN segment is sent to the TCP server. Server-side TCP responds by sending an ACK, which is received by the client-side TCP. As per the TCP connection state diagram $\text{(RFC 793)}$, in which state does the client-side TCP connection wait for the FIN from the server-side TCP?

• A. LAST-ACK
• B. TIME-WAIT
• C. FIN-WAIT-$1$
• D. FIN-WAIT-$2$

Comments

Ans: FIN-WAIT-2 (D)

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Last minute quick explanation with great visuals:

TCP States - Computer Networks For Developers 07 - YouTube

Answer 1

 

FIN WAIT-1 -->  if client sent FIN segment to the server and waiting for the ACK of its own FIN segment

Now after FIN WAIT-1 there are two possibility -- 

(1) if client receives ACK for its own FIN then client move to FIN-wait-2 and waiting for FIN from server side

after reciving the FIN from server client will send ACK   then connection is not closed immediately it wait for some time and then closed  and this wait time is called TIME-WAIT state.

(2)if client not recive ACK instead of ACK if it recived FIN from server side now client will ackonwledge this FIN and move to close state

Here Client will wait for the ACK for its own FIN.
After receiving ACK, client will move to TIME-WAIT state.

Answer 2

$Answer : D$

$Source$ : Data Communications and Networking By Behrouz A.Forouzan

Answer 3

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