Model Driven Communication Protocol Engineering and Simulation based Performance Analysis using UML 2.0

The automated functional and performance analysis of communication systems specified with some Formal Description Technique has long been the goal of telecommunication engineers. In the past SDL and Petri nets have been the most popular FDTs for the purpose. With the growth in popularity of UML the most obvious question to ask is whether one can translate one or more UML diagrams describing a system to a performance model. Until the advent of UML 2.0, that has been an impossible task since the semantics were not clear. Even though the UML semantics are still not clear for the purpose, with UML 2.0 now released and using ITU recommendation Z.109, we describe in this dissertation a methodology and tool called proSPEX (protocol Software Performance Engineering using XMI), for the design and performance analysis of communication protocols specified with UML. Our first consideration in the development of our methodology was to identify the roles of UML 2.0 diagrams in the performance modelling process. In addition, questions regarding the specification of non-functional duration contraints, or temporal aspects, were considered. We developed a semantic time model with which a lack of means of specifying communication delay and processing times in the language are addressed. Environmental characteristics such as channel bandwidth and buffer space can be specified and realistic assumptions are made regarding time and signal transfer. With proSPEX we aimed to integrate a commercial UML 2.0 model editing tool and a discrete-event simulation library. Such an approach has been advocated as being necessary in order to develop a closer integration of performance engineering with formal design and implementation methodologies. In order to realize the integration we firstly identified a suitable simulation library and then extended the library with features required to represent high-level SDL abstractions, such as extended finite state machines (EFSM) and signal addressing. In implementing proSPEX we filtered the XML output of our editor and used text templates for code generation. The filtering of the XML output and the need to extend our simulation library with EFSM abstractions was found to be significant implementation challenges. Lastly, in order to to illustrate the utility of proSPEX we conducted a performance analysis case-study in which the efficient short remote operations (ESRO) protocol is used in a wireless e-commerce scenario

Entwurfsbegleitende Leistungsanalyse für SDL-basiertes Design multimedialer Internet-Transportsysteme

Neben der funktionalen Korrektheit von komplexen Kommunikationssystemen spielt eine ausreichende Performance dieser Systeme eine immer wichtigere Rolle. Dabei ist es notwendig, Performance-Aspekte bereits in frühen Entwurfsphasen und nicht erst nach der Implementierung der Systeme zu berücksichtigen. Die vorliegende Arbeit präsentiert eine Methodik zur entwurfsbegleitenden, modellgestützten Leistungsanalyse von Kommunikationsprotokollen, die mit Hilfe der Sprache SDL formal spezifiziert wurden. Die vorgestellte Methodik verwendet dazu Beschreibungsmechanismen, Verfahren und Werkzeuge, die bereits im Entwurfsprozeß dieser Systeme verwendet werden. Für die wichtigsten Implementierungsansätze von Kommunikationsprotokollen werden Performance-Bausteine vorgestellt und deren Verwendung erläutert. Die Tragfähigkeit der entwickelten Methodik wird durch eine große Fallstudie im Kontext von Reservierungsprotokollen zur Unterstützung von Multimedia-Anwendungen im Internet demonstriert. Dabei werden nicht nur die informellen Angaben der vorhandenen RFCs in formale SDL-Beschreibungen umgesetzt, sondern auch als existent vorausgesetzte Ressource-Management-Funktionen entwickelt und analysiert. Die vorliegende Arbeit schließt so die bisher bestehende Lücke im SDL-basierten Entwurfsprozeß verteilter reaktiver Systeme und ermöglicht die modellgestützte Betrachtung von Performance-Aspekten in den frühen Phasen des Entwurfsprozesses

Reachability analysis of fault-tolerant protocols

Due to the increasing requirements imposed on fault-tolerant protocols, their complexity is steadily growing. Thus verification of the functionality of the fault-tolerance mechanisms is also more difficult to accomplish. In this thesis a model-based approach towards efficiently finding ``loopholes'' in the fault-tolerance properties of large protocols is provided. The contributions comprise thinning out the state space without missing behavior with respect to the validation goal through a partial ordering strategy based on single fault regions. Two algorithms for (partial) analysis are designed, implemented and evaluated: the H-RAFT algorithm is based on SDL elements constituting each transition and requires no user-knowledge. The Close-to-Failure algorithm on the other hand is purely based on user-provided information. Combination of the two algorithms is also investigated. All contributions exploit the fault-tolerant nature of the protocols. In order to compare the performances of the novel techniques to well-known algorithms, a tool has been developed to allow for easy integration of different algorithms. All contributions are thoroughly investigated through experiments summing up to several CPU-month. The results show unambiguously the advantages of the developed methods and algorithms.Durch die zunehmenden Anforderungen an fehlertolerante Protokolle steigt auch deren Komplexität zusehends. Dadurch ist es deutlich schwieriger die Funktionalität der Fehlertoleranzmechanismen zu überprüfen. In dieser Arbeit wird ein modellbasierter Ansatz vorgestellt, dessen Ziel es ist ``Lücken'' in den Fehlertoleranzeigenschaften effizient zu finden. Dazu wird ein Algorithmus entwickelt, der eine partiellen Ordnung erzeugt und es somit erlaubt den Zustandsraum zu verkleinern ohne Verhalten bezüglich der zu prüfenden Eigenschaften zu verlieren. Weiterhin werden zwei Algorithmen zur (partiellen) Analyse entworfen, implementiert und bewertet: Der H-RAFT Algorithmus basiert auf den SDL-Elementen der jeweiligen Transitionen und erfordert keinerlei weiteres Domänen-Wissen des Benutzers. Der Close-to-Failure Algorithmus hingegen ist nur von Benutzerinformationen abhängig. Kombinationen der beiden Ansätze werden ebenfalls untersucht. Für alle vorgestellten Methoden und Algorithmen wird ausgenutzt, dass es sich um fehlertolerante Protokolle handelt. Um die neuen Ansätze mit weitverbreiteten Algorithmen vergleichen zu können wird ein Werkzeug entwickelt, welches eine einfache Integration von Algorithmen ermöglicht. Die vorgestellten Techniken werden ausführlich in Experimenten mit einem Gesamtaufwand von etlichen CPU-Monaten untersucht. Die Ergebnisse dieser Experimentreihen zeigen eindeutig die Vorteile der entwickelten Algorithmen und Methoden

MINA - a tool for MSC-based performance analysis and simulation of distributed systems

Performance analysis can help to address quantitative system analysis from the early stages of the system development life cycle, e.g., to compare design alternatives or to identify system bottlenecks. This thesis addresses the problem of performance evaluation of distributed systems by employing a viewpoint where analytical and simulative evaluation techniques are unified in the MINA tool to make use of both techniques. We suggest a modelling tool chain to evaluate the performance of distributed systems like computer and communication systems based on an MSC description of the system. MSC-based performance evaluation of distributed systems is an approach that uses performance models, which are based on an MSC description of a system to evaluate system performance measures. To determine the system performance, these descriptions can be extended by notions for time consumption and resource usage and afterwards be included in a system performance model. Based on this unique model specification, analytical as well as simulative techniques can be applied to achieve either quick mean value results by queueing networks analysis or confidence intervals or transient measures by simulation. The applicability to real world systems and the advantages of the tool has been demonstrated by a large application example in the field of mobile communication systems, and its effectiveness has been evaluated by comparing it with other approaches. The experimental results show that the tool is scalable, the way it can model simple as well as complex systems. Moreover, it is straightforward and has the ability to find reasonable solutions in an efficient manner

Performance Modeling Framework for CORBA Based Distributed Systems

The CORBA platform is increasingly popular in distributed computing due to its ability to hide complex implementation issues from application developers. However, performance consequences of the underlying techniques often remain visible to software developers. Moreover, new performance concerns may emerge because of additional layering and indirection. Performance modeling allows developers to understand and predict the performance of CORBA based systems. In this wor

Hydrogenation of carbon monoxide over modified cobalt-based catalysts

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Phllosophy.A disadvantage of the Fischer-Tropsch synthesis is that a broad product spectrum is obtained. Economic considerations however require an improvement in the optimization of the reaction to maximize the production of high value commercial products, in·particular, short chain olefins and high molecular weight hydrocarbons. [Abbreviated abstract. Open document to view full version]AC201

Television broadcast from space systems: Technology, costs

Broadcast satellite systems are described. The technologies which are unique to both high power broadcast satellites and small TV receive-only earth terminals are also described. A cost assessment of both space and earth segments is included and appendices present both a computer model for satellite cost and the pertinent reported experience with the Japanese BSE

Price - San Rafael Rivers Unit, Utah, Planning Report / Final Environmental Impact Statement, Colorado River Water Quality Improvement Program / Colorado River Salinity Control Program

This integrated Planning Report/Final Environmental Impact Statement (PR/FEIS) presents an analysis of the planning process and the environmental impacts of the proposed Price-San Rafael Rivers Unit (Unit) of the Colorado River Water Quality Improvement Program (CRWQIP) and the Colorado River Salinity Control Program (CRSC). The document has been jointly prepared by the Bureau of Reclamation (Reclamation) and the Soil Conservation Service (SCS) to address the full range of potential environmental impacts, in compliance with the National Environmental Policy Act (NEPA). The CRWQIP/CRSC programs provide for projects upstream of Imperial Dam (near Yuma, Arizona, on the Arizona-California border) that are necessary to maintain or reduce salinity in the Colorado River. A final environmental statement on the CRWQIP was prepared by Reclamation and SCS (May 19, 1977). This PR/FEIS will be used to meet NEPA compliance requirements and to obtain construction authorization for off-farm features. Onfarm features are authorized for construction under Public Law 93-320, as amended by public Law 98-569