Robust Systems

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Robust Systems
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Faults at James Reserve
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Faults on a volcano in Ecuador WLJ06
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Data faults in Bangladesh
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Calibration
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Motivation Summary
Hard Problems
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Summary

• People pay for robustness in other systems
• Higher quality hardware
• Technicians to monitor the data
• Wired infrastructure
• In sensor networks when we pay, we pay for scale
• The burden on software has increased
• Robustness in sensor networks requires research
  and engineering

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CentRoute
Distributed Mote Routing
Centralized Mote Routing
All routing decisions state at microserver
Routing table, neighbor table, local decisions
Bypasses mote hardware limitations through global
view at microserver
Distributed decision making on very limited RAM
hardware

• Designed for robustness
• Minimizes routing inconsistencies, including
  loops
• Minimizes memory (state) requirements on motes
• Increases routing stability
• Can scale to dense networks

• Additional functionality
• Bidirectional unicast routing (to and from the
  sink)
• Global view of the entire mote network at each
  sink

Work by Thanos Stathopoulos
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Memory Protection

• LIGHTHOUSE
• Develop simple and intuitive memory model
• Each block of memory is under the control of
  exactly one program at any time
• Controlling program is responsible for either
  tracking, freeing, or transferring ownership of
  the data
• Found significant memory management errors in
  both kernel and user SOS code using new analysis
  tool
• Accomplishes analysis via basic data-flow
  analysis on source code

• SANDBOX
• Create multiple protection domains within single
  address space CPUs
• Restrict write accesses of a domain to memory it
  owns
• Restrict control flow in and out of a domain
• Designed for small memory CPUs
• No static partitioning of address space
• Compact memory map tracks ownership and layout
• Enforced by inline run-time checks
• All write accesses are checked
• All control flow operations are checked
• Checks introduced through binary re-write
• Binary verified at every node
• Verifier independent of re-writer
• Correctness of scheme depends only upon
  correctness of verifier

Work by Ram Kumar and Roy Shea
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Tenet

• Show counter on LEDs
• Sense and send data back to the sink
• ... with time-stamp and sequence number
• Get memory status for node 10
• If temperature is above 50, send temperature,
  node ID and next routing hop

MemStats
Send
Address
NEQ(10)
DeleteIf
Paek, Greenstein et al.
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Sympathy Confidence
Radio
Sensorboard
Nithya Ramanathan
Network
Environment
Mote
Final Destination
Batteries
Sensors
Data Generation Path
Data Delivery Path
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Fault Detection

• Exploit sensor data by finding correlations
  between different variables
• Recognize a fault when sensor data breaks its
  strongest correlations
• Variable space is too high dimensional
• Signal processing techniques may provide an
  efficient correlation model

Recent Measurements
Measurements at same time previous day
Proximate Nodes
Nodes of Same Altitude or Depth
Another modality on the same node
Contextual or multiscale information