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Software Fault Protection

Software Fault Protection. Allen Goldberg Kestrel Technology. System Engineering. System engineers build reliable systems from less reliable components. Redundancy is a primary means of achieving reliability. Systems are monitored for anomalies.

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Software Fault Protection

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  1. Software Fault Protection Allen Goldberg Kestrel Technology

  2. System Engineering • System engineers build reliable systems • from • less reliable components. • Redundancy is a primary means of achieving reliability. • Systems are monitored for anomalies. • Fault containmentmechanisms (e.g. firewalls) limit damage Workshop on Aviation Software, Oct. 2006

  3. What About software? Assume perfection, little accommodation for failure even though perfection is rarely achievable Can we make reliable software systems from less reliable software components? Workshop on Aviation Software, Oct. 2006

  4. IVHM Fault Protection Systems Fault Protection System monitoring model fault response System under control Workshop on Aviation Software, Oct. 2006

  5. Software Fault Protection System monitoring Model of software fault response SUT is software Software Fault Protection (SFP) Workshop on Aviation Software, Oct. 2006

  6. Software Redundancy • redundancy: different representations of software behavior • code • test case • model • … • Redundancy is expensive • How should you invest your “redundancy” dollars? Workshop on Aviation Software, Oct. 2006

  7. Effective Redundancy at Runtime • software “model” • “1.2” version programming • 1 full-featured, efficient, complex version • 0.2 backup version performs essential functions Software Fault Protection System monitoring Model of software fault response software Workshop on Aviation Software, Oct. 2006

  8. Software Model • When software fails it is usually “obviously” wrong • Simple models can detect • errors • interface behavior • data reasonableness • resource usage • Our model extends ARINC 653 configuration file Software Fault Protection System monitoring Model of software fault response software Workshop on Aviation Software, Oct. 2006

  9. Failure responses • safe modes: terminate non-essential activities • component reset (supported by 653) • transient errors lead to bad state • component replacement (supported by 653) • “1.2” version programming Workshop on Aviation Software, Oct. 2006

  10. Fault Containment • Eliminate “non-logical” software dependencies • error propagation (crash) • resource contention • ARINC 653 • Fault containment is essential to fault isolation Workshop on Aviation Software, Oct. 2006

  11. Future Work • relate SFP with multi-string flight computers, and system fault protection • relate SFP to treatment of radiation induced SEU’s • generate SFP models from software design artifacts • generate SFP implementations from SFP models Workshop on Aviation Software, Oct. 2006

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