Reverse Engineering of Complex Legacy Telecommunication Systems

Kurzfassung: Reverse and reengineering of large and complex software systems is a difficult task. As a result, many methods and tools for reverse and reengineering have been developed so far. However, the work in this field has concentrated on sequential, and untimed systems, mainly for business applications. The majority of the approaches deals with decomposing monolithic systems, decoupling user interface/presentation from application logic and data handling/database management, or with identifying reusable components. In particular, numerous approaches have addressed the migration of legacy business applications to an object-based or object-oriented architecture. To a large extent, the corresponding methods are data-centered since they focus on structuring the data maintained by an application. Another stream of research has dealt with migration to code of programming languages such as C++ and Java which already provide language support for object-oriented programming. Reverse and Reengineering of process-oriented applications has been addressed less extensively. For example, a telecommunication system is composed of a set of distributed communicating processes which are instantiated dynamically for handling calls requested by the users of the system. Such a system is designed in terms of services provided by entities which communicate according to protocols. Understanding a telecommunication system requires the recovery of these concepts from the current source code and other sources of information. Furthermore, analyzing and visualizing the dynamic behavior is a key to system understanding. This dissertation describes the concepts and the implementation of integrated tools for reverse and reengineering of telecommunication systems which were developed in close cooperation with ERICSSON in the ECARES project (Ericsson Communication ARchitecture for Embedded Systems). The concepts are based on studies and evaluation of a real telecommunication system Ericsson’s Mobile-service Switching Center (MSC) for GSM networks called AXE10. These studies led to specific requirements. These requirements and an abstract system structure are described within a conceptual framework, which specifies the problem domain and identifies and interrelates the necessary concepts, thus building the terminological and conceptual foundation of this dissertation. To guarantee the suitability and applicability of the methods and tools developed in this thesis, tool support was developed step by step in response to the requirements and questions stated by telecommunication experts. This approach implied an iterative and incremental analysis and development process. Each pass of this process concentrates on a subset of the overall functionality and delivers appropriate analysis functionality and result documents, thus providing another portion of the final reverse and reengineering environment. The essential contributions (concepts, methods, and tools) to reverse engineering of telecommunication systems are as follows: