State Transition Diagrams and Petri Nets

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State Transition Diagrams and Petri Nets

• Siv Hilde Houmb
• Telenor RD

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Case description

• System, attackers and security mechanism
  (Firewall)
• System (LAN)
• System OK
• System is subject to attack
• Firewall
• FTP, port 21
• DNS, port 23
• SMTP, port 25
• HTTP, port 80
• Ports can be open or closed
• Attackers

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State Transition Diagram
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Limitation

• Hard to address simultanious events (system,
  security mechanism, attackers and ...)
• State explotion

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PN Model
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Analysis

• Correctness analysis
• Performance analysis
• Calculating the steady state probability
  distribution of the embedded Markov Chain.
• Simulation (step by step)
• A Markov state in the context of a PN is given
  by each unique arrangement of tokens in each of
  the places (a marking) of the net each distinct
  marking correspond to a state in the Markov Chain.

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Performance Analysis

• Software (DNAnet for GSPN)
• Performance analysis
• Tokens per place
• Full Token Distribution
• Steady State
• Transition enabling
• Transition throughput

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Comments...

• But, why not use PN for both system description
  model and model for analysis?