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Transmission Control Protocol—TCP 61-13<br />

Sender<br />

Receiver<br />

Segment 1: FIN<br />

seq:12500, ack:--<br />

Segment 2: ACK<br />

seq:5000, ack:12501<br />

Segment 3: FIN<br />

seq:5001, ack:12501<br />

Segment 4: ACK<br />

seq:12501, ack:5002<br />

Time<br />

Time<br />

FIGURE 61.10<br />

Four-way handshaking during connection termination.<br />

• One of the processes wants to abandon the connection because of an abnormal situation. It can<br />

send the RST segment to destroy the connection.<br />

• One of the processes determines that the other side is idle for a long time. The other system is<br />

considered idle if it does not send any data, any acknowledgments, or keep-alive segments. The<br />

awaiting process may send the RST segment to destroy the connection.<br />

Closed<br />

Passive open/--<br />

SYN/SYN+ACK<br />

Listen<br />

RST/--<br />

Active open/SYN<br />

Close/--<br />

Time-out/RST<br />

RST/--<br />

Send/SYN<br />

SYN-RCVD SYN/SYN+ACK<br />

SYN-SENT<br />

Close or<br />

time-out /--<br />

(Simultaneous open)<br />

SYN+ACK/ACK<br />

ACK/--<br />

Established<br />

Close/FIN<br />

Close/FIN<br />

FIN/ACK<br />

FIN<br />

wait-1<br />

ACK/--<br />

FIN/ACK<br />

FIN+ACK/ACK<br />

Closing<br />

ACK/--<br />

Close/<br />

FIN<br />

Close<br />

wait<br />

FIN<br />

wait-2<br />

FIN/ACK<br />

Timewait<br />

(Time-out)<br />

Last<br />

ack<br />

ACK/--<br />

FIGURE 61.11<br />

TCP state transition diagram.<br />

© <strong>2011</strong> by Taylor and Francis Group, LLC

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