You Name It, We Analyze It! 1
You Name It,We Analyze It!
Jim GilsinnKenexis Consulting Corporation
You Name It, We Analyze It! 2
Industrial Network Types & Metrics:Publish/Subscribe
• Publish/subscribe or peer-to-peer communications
• Main performance metric: Cyclic frequency variability/jitter
• Real-time EtherNet/IP™ uses publish/subscribe• Requested/Accepted Packet Interval (RPI/API)• Measured Packet Interval (MPI)
You Name It, We Analyze It! 3
Industrial Network Types & Metrics:Publish/Subscribe
• Difference between TPub_Com_Init & TSub_Com_Init is network roundtrip delay
• TPub_Com_Init, TSub_Com_Init not important
• Variability in TPub much more important
• Theoretically, TPub doesn’t need to match Tsub
• In production systems, they are the same
TPub_Com_Init
Subscriber Publisher
TPub_1
TPub_2
TPub_N-1
TPub_N
TSub_Com_Init
TSub_M
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Performance Testing Methodology:Performance Metrics
• Command/response or master/slave communications
• Main performance metric: Latency
• Large numbers of protocols use this• Most (All?) PC-based server/client protocols – HTTP(S), (S)FTP, etc.• Most industrial protocols – Modbus/TCP, Profinet, Ethercat, etc.
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Industrial Network Types & Metrics:Command/Response
• Difference between TCom_Delay & TRes is network roundtrip delay
• Latency in TCom & TRes important
TRes_1
Commander Responder
TRes_2
TCom_Delay_1
TCom_1
TCom_2
TCom_Delay_2
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Isolating Traffic Streams
• Isolating traffic streams can be tricky
• 10’s – 100’s of traffic streams in production environment
• Your Wireshark Fu must be strong!
• Usually requires additional post-processing
• Multiple streams can exist between same devices
You Name It, We Analyze It! 7
Isolating Traffic Streams
• Traffic pairs• Source IP/MAC address• Destination IP/MAC address• Source TCP/UDP port• Destination TCP/UDP port
• Publish/Subscribe• Communication stream ID• Sequence number (optional)
• Command/Response• Command message/field• Response message/field• Message ID (optional)
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Test Time vs. Packet Interval
Test Time (s)
Measured Packet Interval (ms)~62 sec testMean MPI = 2msMin ~ 1.2Max ~ 2.9
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Time Plot for Command/Response
Regular Pattern to Delayed Packets
Regular Pattern of Minimal Delayed Packets
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Command/Response Timing Plots
• Quick succession of command/response packets
• Minimal delay in command/response sequence
• Apparently large delay in a single packet
• Example: Rockwell tag reads
Quick Succession Read Commands
Delay Until Next Time Sequence
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Next Steps
• Streamline traffic stream processing
• Develop better command/response code
• Build more mathematical statistical models
• Add graphical modeling of time & frequency domain
• Add more industrial protocols and obtain example files• Modbus• Profinet• DNP3• 61850• And others…
You Name It, We Analyze It! 12
Questions
• Contact Me• Jim Gilsinn• 301-706-9985 or 614-323-2254• [email protected]• Twitter – @JimGilsinn• LinkedIn – http://www.linkedin.com/in/jimgilsinn/• SlideShare – http://www.slideshare.net/gilsinnj
