Dependability Engineering of Complex Computing Systems M. Kaniche - - PowerPoint PPT Presentation
Dependability Engineering of Complex Computing Systems M. Kaniche J.-C. Laprie J.-P. Blanquart LAAS / LIS LAAS / LIS Astrium / LIS kaaniche@laas.fr laprie@laas.fr blanquar@laas.fr 6th International Conference on Engineering
6th International Conference on Engineering of Complex Computer Systems (ICECCS 2000) September 11-14 2000, Tokyo, Japan LAAS / LIS LAAS / LIS Astrium / LIS kaaniche@laas.fr laprie@laas.fr blanquar@laas.fr
Property of a system such that reliance can justifiably be placed on the service it delivers Impairments Means Attributes Fault Prevention Fault Tolerance Fault Removal Fault Forecasting Availability Reliability Confidentiality Integrity Maintainability Fault Error Failure
(IFIP WG 10.4- Dependable Computing and Fault Tolerance)
Safety
Developing dependable systems able to deliver critical services with a
justified level of confidence is not easy
increasing complexity, fault diversity, conflicting objectives, …
Traditional development models do not explicitly incorporate all
activities needed for the production of dependable systems
Hardware (BSI 5760 Standard)
incorporation of assessments fault tolerance activities focussed on physical faults only
Software (Waterfall, V model, spiral, incremental, process oriented,…)
structuring of activities focus on verification
System engineering (EIA 632, IEEE 1220, …)
generic pluridisciplinary framework integrating products, processes and people dependability related issues are not detailed
Need for a dependability-explicit development model
Dependability processes
System Creation Process System Creation Process
Fault Prevention Process Fault Prevention Process
risk assessment
Fault Tolerance Process Fault Tolerance Process
presence of faults
mechanisms
Fault Removal Process Fault Removal Process
Fault Forecasting Process Fault Forecasting Process
Design Realization Integration Requirement
Beh Behavior in the presence of faults Par System Partitioning Han Error & Fault Handling Obj Objectives All Allocation Eva Evaluation Ver Verification Dia Diagnosis Mod Modification For Formalisms & languages Org Project Organization Pla Project Planning & Risk assessment
Ver Dia Mod For Org Pla Han Par Beh Obj All Eva
System Creation System Creation Fault Prevention Fault Prevention Fault Tolerance Fault Tolerance Fault Removal Fault Removal Fault Forecasting Fault Forecasting
Fault prevention process activities should be tightly coupled with
system creation and dependability processes activities
Fault tolerance and fault forecasting
Definition of dependability related requirements and functions Allocation of dependability requirements Assessment of the efficiency of fault tolerance mechanisms (coverage)
Fault removal and fault tolerance
Verification of fault assumptions for traceability, consistency,
completeness and verifiability
Verification of fault tolerance mechanisms by means of fault injection,
formal verification or static analyzes
Fault removal and fault forecasting
Validation of fault forecasting assumptions and results Definition of test stopping criteria based on dependability level achieved Evaluation of dependability based on test results
Fault assumptions should be defined at each system refinement step
Support for the definition of fault tolerance strategies and mechanisms Check for traceability, consistency, completeness and verifiability
Fault Tolerance Coverage Error and Fault Handling Coverage Fault Assumption Coverage Failure Mode Coverage Failure Independence Coverage
FP Rq De Re In FR FT FF Rq Requirements De Design Re Realization In Integration FP Fault Prevention FT Fault Tolerance FR Fault Removal FF Fault Forecasting
System requirements allocated to software Software Product
reuse with adjustments
Rq De Re In Rq De Rq Re Rq Rq De In De In In In In In Rq De Re
traditional Waterfall reuse without changes Prototyping
System development process Software development process
Requirements
❍ System behavior / failures
consecutive failures to be tolerated for each mode
by the environment
❍ Verification planning
strategies (criteria, input generation)
❍ Verification assumptions
❍ Requirements verification
❍ Functional/ behavioral verification scenarios
❍ Formalisms & languages
❍ Project organization
❍ Project planning & risk assess.
certification, config. management
Fault Prevention Fault Tolerance Fault Removal Fault Forecasting
❍ Dependability objectives ❍ Failure modes analysis
❍ FF assumptions ❍ Function-by-function
dependability allocation
by criticality levels
❍ Fault forecasting planning ❍ Data collection and analysis ❍ Functional specification
modes
❍ Environment description
❍ Development and validation,
constraints
Design
❍ System behavior / faults
❍ System partitioning
regions
❍ Fault tolerance strategies
diversity, exception handling
❍ Error & Fault handling
mechanisms
recovery
reconfiguration
❍ Single points of failure? ❍ Verification assumptions ❍ Design verification
inspections, prototyping
❍ Fault tolerance verification
injection
❍ Unit / Integration testing
planning
❍ Functional/structural
verification scenarios
❍ Verification of FF results ❍ Formalisms & languages ❍ Project organization ❍ Project planning & riskassess.
Fault Prevention Fault Tolerance Fault Removal Fault Forecasting
❍ FF assumptions ❍ Failure Mode Analysis
❍Allocation / component
❍ Preliminary dependability assessment ❍ Data Collection & Analysis ❍ Architecture
❍ Low level requirements ❍ Reusable components? ❍ Operation and maintenance
procedures definition ❍ System integration strategy
Structuring and controlling the development process is a prerequisite
for the successful integration of fault tolerance and dependability- related mechanisms in complex systems
The proposed model provides a generic framework for structuring
fault prevention, fault tolerance, fault removal and fault forecasting activities
iterative process tradeoffs
The guidelines aim to ensure that dependability related issues are not
The proposed framework can be used to define and structure the
evidence needed to support certification