A Framework for the Performance Evaluation of SDL/MSC-specified Systems

SDL and MSC are standardized specification techniques for the development of reactive real-time systems and protocol architectures. Whereas MSC scenarios only allow to specify the dynamic system behavior in form of event/time diagrams, SDL specifications are used to describe static and functional aspects of the system as well. In this paper a framework is presented which demonstrates the relationship between formally specified SDL systems and appropriate performance analysis respectively monitoring techniques driven by annoted MSC scenarios. It is further discussed how to analyse some important performance measures for SDL-specified systems, i.e. the utilization of processor and channel components, which correspond to the workload characteristics of given MSC scenarios. INTRODUCTION AND MOTIVATION Due to the ever increasing complexity of parallel and distributed systems appropriate computer aided system engineering (CASE) techniques must be used to design safe and high performance systems. CASE tools have to support all phases in the software development and life cycle, namely requirement analysis, design, specification, implementation, test and monitoring of the real system. Standardized formal description techniques (FDTs) like LOTOS (ISO 8807) which is based on an process algebra approach, ESTELLE (ISO 9074) and SDL (ITU Z.100), both describing the system behavior by means of extended finite state automata [Hog89], provide a unifying theoretical basis for the construction of dedicated CASE tools. Modern objectoriented specification languages like SDL’92 also allow the hierarchical decomposition of systems by reusing less complex subsystems with simpler functional and temporal properties. This work is supported by the German Research Council (DFG) in scope of the Special Research Area 182 “Multiprocessor and Network Configurations” There exist, however, only few results concerning the development of methods and tools for studying the performance of systems which are specified and implemented by using an FDT approach ([DHHMC95], [BB93], [HHMC91]). Performance evaluation starting from an abstract system model either can be achieved by mathematical analysis and simulation techniques in early system design phases or by monitoring parts of the real system in the integration and test phase. Because most modern FDT environments support the automatic generation of executable code from a given formal system specification, monitoring tools can reuse these system specifications as a formal monitoring model as well [DDL95]. In the next section it is first motivated why SDL and MSC are good suited for specifying and developping distributed realtime systems. The presentation of a general framework to evaluate the performance of SDL/MSC-specified systems follows next. Then it is shown how the analysis of the mean performance characteristics of processor and channel components can be achieved by using annotated SDL/MSC specifications. Finally the main results are summarized and a short outlook to future work will conclude the paper.