State Diagrams

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State Diagrams

• EE 122 Intro to Communication Networks
• Fall 2007 (WF 4-530 in Cory 277)
• Vern Paxson
• TAs Lisa Fowler, Daniel Killebrew Jorge Ortiz
• http//inst.eecs.berkeley.edu/ee122/
• Materials with thanks to Jennifer Rexford, Ion
  Stoica,and colleagues at Princeton and UC
  Berkeley

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State Diagrams

• For complicated protocols, operation depends
  critically on current mode of operation
• Important tool for capture this state diagram
• At any given time, protocol endpoint is in a
  particular state
• Dictates its current behavior
• Endpoint transitions to other states on events
• Interaction with lower layer
• Reception of certain types of packets
• Interaction with upper layer
• New data arrives to send, or received data is
  consumed
• Timers

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TCP State Diagram
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SMTP State DiagramServer States
client sends other commands
closed
begin
connection establishment 2xx
HELO
connection establishment 4xx
wait
MAIL FROM 2xx
client sends other commands or errors on MAIL
FROM
envelope created no recipients
RSET
errors
attempt to deliver
client sends other commands or errors on RCPT TO
RSET
RCPT TO 2xx
text
recipients set
writing mail
ready to deliver
DATA
client sends other commands or errors on RCPT
TO or RCPT TO 2xx
ltCRLFgt.ltCRLFgt
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SMTP State DiagramCommand States
HELO MAIL RCPT RSET SEND SOML SAML VRFYEXPN HELP
NOOP QUIT TURN
begin
wait
1xx 3xx
4xx 5xx
2xx
success
error
failure