1. RFC 793 State machine study

2. Simultaneous close sequence Page 39, Figure 14

3. Simultaneous close sequence
Page:39
Figure. 14
TCP A
TCP B
SEQ=100
Should_ACK=300
SEQ=300
Should_ACK=100
1. ESTABLISHED ESTABLISHED

4. Simultaneous close sequence
Page:39
Figure. 14
TCP A
TCP B
SEQ=101
SEQ=100
Should_ACK=301
Should_ACK=300
SEQ=301
SEQ=300
Should_ACK=101
Should_ACK=100
SEQ=100 CTL=FIN
ACK=300 DATA=
SEQ=300 CTL=FIN
ACK=100 DATA=
2. (Close) (Close)
FIN-WAIT-1 --> <SEQ=100><ACK=300><CTL=FIN,ACK> ... FIN-WAIT-1
<-- <SEQ=300><ACK=100><CTL=FIN,ACK> <
... <SEQ=100><ACK=300><CTL=FIN,ACK> -->

5. Simultaneous close sequence
Page:39
Figure. 14
TCP A
TCP B
SEQ=101
SEQ=101
Should_ACK=301
Should_ACK=301
SEQ=301
SEQ=301
Should_ACK=101
Should_ACK=101
SEQ=101 CTL=
ACK=301 DATA=
SEQ=301 CTL=
ACK=101 DATA=
3. CLOSING > <SEQ=101><ACK=301><CTL=ACK> CLOSING
<-- <SEQ=301><ACK=101><CTL=ACK> <
... <SEQ=101><ACK=301><CTL=ACK> >

6. Simultaneous close sequence
Page:39
Figure. 14
TCP A
TCP B
SEQ=NA
SEQ=101
Should_ACK=NA
Should_ACK=301
SEQ=301
SEQ=NA
Should_ACK=NA
Should_ACK=101
4. TIME-WAIT TIME-WAIT
(2 MSL) (2 MSL)
CLOSED CLOSED