Assessing software reliability performance under highly critical but infrequent event occurrences

Operational testing is expensive and time-consuming in applications with highly critical but infrequent event occurrences, and procedures are needed for obtaining valid software reliability estimates. Two such procedures are accelerated stress testing and experimental design techniques. Examples of accelerated stress in software include: a higher request arrival rate, increasing data traffic "burstiness", and so on. Furthermore, when the software is tested by executing the system under emergency conditions or exception events, it is critical that experimental design techniques are used to account for "carry-over" effects in failure performance. An application of software reliability testing of a telecommunication system node controller is used to describe the issues and our overall approach to software reliability assessment. The reliability projections based on our approach are compared to reliability estimates derived analytically and through simulation. Our results suggest that these statistical techniques are useful techniques for measuring reliability performance under critical events that have a low probability of occurrence.