RFC 793State machine study

Simultaneously active SYNPage 32, Figure 8

Simultaneously active SYN Page:32Figure. 8

1. CLOSED CLOSED

TCP A TCP BSEQ=NA SEQ=NAShould_ACK=NA Should_ACK=NA

Simultaneously active SYN

TCP A TCP B

Page:32Figure. 8

1. CLOSED CLOSED2. SYN-SENT --> <SEQ=100><CTL=SYN> ...

SEQ=100 CTL=SYNACK= DATA=

SEQ=NASEQ=100 Should_ACK=NA SEQ=NA Should_ACK=NA

Simultaneously active SYN

TCP A TCP B

Page:32Figure. 8

2. SYN-SENT --> <SEQ=100><CTL=SYN> ...3. SYN-RECEIVED <-- <SEQ=300><CTL=SYN> <-- SYN-SENT

SEQ=100 CTL=SYNACK= DATA=

Should_ACK=NA SEQ=NA Should_ACK=NASEQ=100 SEQ=300

SEQ=300 CTL=SYNACK= DATA=

Should_ACK=301

Simultaneously active SYN

TCP A TCP B

Page:32Figure. 8

3. SYN-RECEIVED <-- <SEQ=300><CTL=SYN> <-- SYN-SENT5. SYN-RECEIVED --> <SEQ=100><ACK=301><CTL=SYN,ACK> ...

SEQ=100 CTL=SYNACK= DATA=

Should_ACK=NASEQ=100

SEQ=300 CTL=SYNACK= DATA=

Should_ACK=301

SEQ=100 CTL=SYNACK=301 DATA=

SEQ=300

Simultaneously active SYN

TCP A TCP B

Page:32Figure. 8

5. SYN-RECEIVED --> <SEQ=100><ACK=301><CTL=SYN,ACK> ...4. ... <SEQ=100><CTL=SYN> --> SYN-RECEIVED

SEQ=100 CTL=SYNACK= DATA=

Should_ACK=NASEQ=100 Should_ACK=301

SEQ=100 CTL=SYNACK=301 DATA=

SEQ=300 Should_ACK=101

Simultaneously active SYN

TCP A TCP B

Page:32Figure. 8

4. ... <SEQ=100><CTL=SYN> --> SYN-RECEIVED6. ESTABLISHED <-- <SEQ=300><ACK=101><CTL=SYN,ACK> <-- SYN-RECEIVED

SEQ=100 CTL=SYNACK=301 DATA=

SEQ=100 Should_ACK=301

SEQ=100 CTL=SYNACK= DATA=

SEQ=300

SEQ=300 CTL=SYNACK=101 DATA=

Should_ACK=101SEQ=101 Should_ACK=301

Simultaneously active SYN

TCP A TCP B

Page:32Figure. 8

6. ESTABLISHED <-- <SEQ=300><ACK=101><CTL=SYN,ACK> <-- SYN-RECEIVED7. ... <SEQ=101><ACK=301><CTL=ACK> --> ESTABLISHED

SEQ=101 Should_ACK=301 SEQ=300 Should_ACK=101

SEQ=101 CTL=ACK=301 DATA=

Should_ACK=101SEQ=301