Supporting Real-Time Communication in CSMA-Based Networks : the VTP-CSMA Virtual Token Passing Approach

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Analysis of the C2 system effectiveness using continous processing time

A typical command-control (C[superscript]2) system was modeled and analyzed for peace-time and war-time as Conflict-free Stochastic Timed Placed Petri Net. The decomposition of the model provides an easier method to formulate and to simulate system states. The procedures to evaluate time-related measures: system maximum throughput rate, measured by minimum average circuit processing rate achieved by the system; average cycle processing rate of a C[superscript]2 process, measured by the processing rate of the task circuit formed by a C[superscript]2 process; and the average system response time, measured by the average time elapsed for the system to perform an input were provided. Time and capacity constraints which are specific to characterize system behavior were addressed. The system effectiveness measures are represented and analyzed as a function of task processing time and capacity available to each process and the system. Hence, this makes it possible to analyze the system structure and thus modify the underlying system

Effects of Communication Protocol Stack Offload on Parallel Performance in Clusters

The primary research objective of this dissertation is to demonstrate that the effects of communication protocol stack offload (CPSO) on application execution time can be attributed to the following two complementary sources. First, the application-specific computation may be executed concurrently with the asynchronous communication performed by the communication protocol stack offload engine. Second, the protocol stack processing can be accelerated or decelerated by the offload engine. These two types of performance effects can be quantified with the use of the degree of overlapping Do and degree of acceleration Daccs. The composite communication speedup metrics S_comm(Do, Daccs) can be used in order to quantify the combined effects of the protocol stack offload. This dissertation thesis is validated empirically. The degree of overlapping Do, the degree of acceleration Daccs, and the communication speedup Scomm characteristic of the system configurations under test are derived in the course of experiments performed for the system configurations of interest. It is shown that the proposed metrics adequately describe the effects of the protocol stack offload on the application execution time. Additionally, a set of analytical models of the networking subsystem of a PC-based cluster node is developed. As a result of the modeling, the metrics Do, Daccs, and Scomm are obtained. The models are evaluated as to their complexity and precision by comparing the modeling results with the measured values of Do, Daccs, and Scomm. The primary contributions of this dissertation research are as follows. First, the metric Daccs and Scomm are introduced in order to complement the Do metric in its use for evaluation of the effects of optimizations in the networking subsystem on parallel performance in clusters. The metrics are shown to adequately describe CPSO performance effects. Second, a method for assessing performance effects of CPSO scenarios on application performance is developed and presented. Third, a set of analytical models of cluster node networking subsystems with CPSO capability is developed and characterised as to their complexity and precision of the prediction of the Do and Daccs metrics

Analytical performance evaluation of concurrent communicating systems using SLD and stochastic Petri nets

Bibliography: leaves 113-117.In this thesis, the performance analysis of SDL with a new type of stochastic Petri net is described. This new net is called SDL-net. The Concurrent Communicating System is described, and the need for qualitative and quantitative analysis of such systems is motivated. Formal methods are demonstrated which can be used to represent such Concurrent Communicating Systems. The Specification and Description Language (SDL) is shown in the context of Concurrent Communicating Systems and the software development cycle is described for SDL systems. Correctness and performance of SDL are discussed and it is shown how the semantics of time for performance can be introduced into SDL by adding external information, by extending the SDL syntax or by using compiler directives. In this thesis only external information is added

Durchführbarkeitsanalyse und Validierung eines Feldbussystems mit einer großen Anzahl an Busteilnehmern mit formalen Methoden

The complexity of large scale fieldbus systems is two-fold: message-sending concurrency and emergent bus behavior. On the one hand, an increase in the number of accumulating nodes within one fieldbus system expands its message-sending concurrency; on the other hand, the growth of emergent bus behavior causes a temporary or lasting message burst on the fieldbus channel. The message sequences in turn have an increased burst behavior, aggravating the traffic density. Therefore, this dissertation evaluates the performability of large scale fieldbus systems by presenting a busload validation procedure by formal methods. The model concept is conceptualized and formulated by UMLCD and OSI Model. Furthermore, the validation procedure is formalized and structurally specified by applying the attribute hierarchy and BMW principle. Based on sorting the message-sending occurrences from the log data of a real fieldbus-based building automation system, the validation procedure is thus quantified with the real system timed-parameters. In addition, the stochastic distributions of message transmissions are determined by the goodness of fit method. The entire work is based on DSPN as formal means of descriptions and models. The corresponding Petri net communication model is hierarchically constructed, which has been further parameterized, integrated and simulated. The analysis of system complexity is provided by the programming-based extension of the Petri net communication model. In addition, the results of Monte-Carlo-Simulation have been sorted, analyzed and evaluated regarding the validation aspects of system performability. Finally, the emergent message burst generated from the function interrelations has also been observed and evaluated. The result of this work will make a formal contribution to the improvement the fieldbus specification.Insbesondere für Feldbussysteme mit einer großen Anzahl an Busteilnehmern wird die Komplexität über zwei Kenngrößen charakterisiert. Einerseits stellt die Erhöhung der Anzahl akkumulierter Feldbusknoten innerhalb eines Feldbussystems eine gestiegene Message-Sendung-Nebenläufigkeit dar. Andererseits steigt diese auch durch Zuwachs des emergenten Busverhaltens, die temporäre oder dauerhafte Nachrichtenfolgen mit sich führen. Die Nachrichtenfolgen wiederum können ein erhöhtes Burst-Verhalten auf dem Feldbus-Kanal, d.h. eine erhöhte Busauslastung verursachen. Ziel der vorliegenden Arbeit ist es, ein komplexes Feldbussystem formal zu beschreiben und ein formales Buslastvalidierungsverfahren darzustellen. Das Modellkonzept wird zunächst durch das UMLCD und das OSI-Modell formuliert, und anschließend wird das Validierungsverfahren mit der Attributhierarchie und dem BMW-Prinzip formalisiert und spezifiziert. Aufgrund der Sortierung des Sendungsverhaltens mittels Logdaten eines realen Feldbus-basierten Gebäudeautomationssystems, wird das Validierungsverfahren durch die quantitative Analyse weitergeführt. Zusätzlich werden die stochastischen Verteilungen der Sendungsverhaltene durch die Goodness-of-Fit Methode angepasst. Die gesamte Arbeit basiert auf DSPN als formales Beschreibungsmittel und Modellierungsmittel. Das entsprechende Petrinetz-Kommunikationsmodell wird vorgestellt, welches hierarchisch konstruiert, parametriert und simuliert wurde. Die Systemkomplexität wird mit Hilfe der Programmierung-basierten Erweiterung des Petrinetz-Kommunikationsmodells analysiert. Dazu werden die Monte-Carlo-Simulationsergebnisse dieses erweiterten Modells vorgestellt, analysiert und bewertet und in Bezug zu den Validierungsaspekten der Systemleistung gesetzt. Schließlich wird das erzeugte Nachrichten-Burst-Verhalten von den Funktionsverknüpfungen beobachtet und bewertet. Die Ergebnisse werden von dieser Arbeit nach der Vervollständigung der formalen Feldbusspezifikation zurückgeführt und verbessert

The crosstalk between EGF, IGF, and Insulin cell signaling pathways - computational and experimental analysis

<p>Abstract</p> <p>Background</p> <p>Cellular response to external stimuli requires propagation of corresponding signals through molecular signaling pathways. However, signaling pathways are not isolated information highways, but rather interact in a number of ways forming sophisticated signaling networks. Since defects in signaling pathways are associated with many serious diseases, understanding of the crosstalk between them is fundamental for designing molecularly targeted therapy. Unfortunately, we still lack technology that would allow high throughput detailed measurement of activity of individual signaling molecules and their interactions. This necessitates developing methods to prioritize selection of the molecules such that measuring their activity would be most informative for understanding the crosstalk. Furthermore, absence of the reaction coefficients necessary for detailed modeling of signal propagation raises the question whether simple parameter-free models could provide useful information about such pathways.</p> <p>Results</p> <p>We study the combined signaling network of three major pro-survival signaling pathways: <b>E</b>pidermal <b>G</b>rowth <b>F</b>actor <b>R</b>eceptor (EGFR), <b>I</b>nsulin-like <b>G</b>rowth <b>F</b>actor-1 <b>R</b>eceptor (IGF-1R), and <b>I</b>nsulin <b>R</b>eceptor (IR). Our study involves static analysis and dynamic modeling of this network, as well as an experimental verification of the model by measuring the response of selected signaling molecules to differential stimulation of EGF, IGF and insulin receptors. We introduced two novel measures of the importance of a node in the context of such crosstalk. Based on these measures several molecules, namely Erk1/2, Akt1, Jnk, p70S6K, were selected for monitoring in the network simulation and for experimental studies. Our simulation method relies on the Boolean network model combined with stochastic propagation of the signal. Most (although not all) trends suggested by the simulations have been confirmed by experiments.</p> <p>Conclusion</p> <p>The simple model implemented in this paper provides a valuable first step in modeling signaling networks. However, to obtain a fully predictive model, a more detailed knowledge regarding parameters of individual interactions might be necessary.</p

A Methodology for Specification-Based Performance Analysis of Protocols

The designer of communication protocols has to formulate rules to govern the communications between processes that are distributed; share common resources concurrently and asynchronously; communicate through unreliable channels that incur random delays; and behave in a time-dependent fashion. The first step is to formally specify the behavior of each of the communicating processes in the protocol. The protocol designer then has to analyze their concurrent behavior to ensure that it satisfies given functional requirements. He also has to analyze their timing behavior to ensure that is meets given timing requirements. The author addresses the specification and analysis of timing requirements and performance measures of protocols

Proceedings of Junior Researcher Workshop on Real-Time Computing

It is our great pleasure to welcome you to Junior Researcher Workshop on Real-Time Computing 2007, which is held conjointly with the 15th conference on Real-Time and Network Systems (RTNS'07). The first successful edition was held conjointly with the French Summer School on Real-Time Systems 2005 (http://etr05.loria.fr). Its main purpose is to bring together junior researchers (Ph.D. students, postdoc, ...) working on real-time systems. This workshop is a good opportunity to present our works and share ideas with other junior researchers and not only, since we will present our work to the audience of the main conference. In response to the call for papers, 14 papers were submitted and the international Program Committee provided detailed comments to improve these work-in-progress papers. We hope that our remarks will help the authors to submit improved long versions of theirs papers to the next edition of RTNS. JRWRTC'07 would not be possible without the generous contribution of many volunteers and institutions which supported RTNS'07. First, we would like to express our sincere gratitude to our sponsors for their financial support : Conseil Général de Meuthe et Moselle, Conseil Régional de Lorraine, Communauté Urbaine du Grand Nancy, Université Henri Poincaré, Institut National Polytechnique de Lorraine and LORIA and INRIA Lorraine. We are thankful to Pascal Mary for authorizing us to use his nice picture of “place Stanislas” for the proceedings and web site (many others are available at www.laplusbelleplacedumonde.com). Finally, we are most grateful to the local organizing committee that helped to organize the conference