State Diagrams EE 122 Intro to Communication Networks Fall 2007 WF 4 5 30 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 1 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 o Reception of certain types of packets Interaction with upper layer o New data arrives to send or received data is consumed Timers 2 TCP State Diagram 3 4 5 SMTP State Diagram Server States closed connection establishment 4xx connection establishment 2xx MAIL FROM 2xx envelope created no recipients client sends other commands or errors on RCPT TO RCPT TO 2xx recipients set client sends other commands or errors on RCPT TO or RCPT TO 2xx begin client sends other commands HELO wait client sends other commands or errors on MAIL FROM RSET errors attempt to deliver RSET text DATA writing mail ready to deliver CRLF CRLF 6 SMTP State Diagram Command States HELO MAIL RCPT RSET SEND SOML SAML VRFY EXPN HELP NOOP QUIT TURN begin wait 1xx 3xx failure 2xx 4xx 5xx success error 7
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