Chair of Computer Networks and Computer Communications
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Publication database

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.

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2008

Conference and workshop papers:

pdf
Patrick Wuechner, Christopher Auer, Richard Holzer and Hermann De Meer
Mathematical Design Models for Self-Organizing Systems
Supplementary online Proc. of the 3rd Int'l Workshop on Self-Organizing Systems (IWSOS 2008)
2008

Tags: AutoI, EuroNF, ResumeNet

Abstract: Self-organization (SO) appears in many different fields: in computer science (e.g., sensor networks), biology (e.g., colony of ants), physics (e.g., elementary magnets), and many more. During the last years, engineering sciences have been attracted by the phenomenon of SO to overcome inevitable issues, for example, scalability issues that arise when engineering and managing large-scale systems consisting of numerous interacting entities. However, prior to engineering selforganizing systems (SOSs), a common terminology is needed to characterize and define SO and SO-related concepts.

Note: Poster with Abstract

2007

Conference and workshop papers:

pdf
Patrick Wuechner and Hermann De Meer
Mathematical Modeling of Self-Organizing Systems
Proc. of the 7th Wuerzburg Workshop on IP: Joint EuroFGI and ITG Workshop on ,,Visions of Future Generation Networks" (EuroView 2007)
Publisher: University of Wuerzburg, Wuerzburg, Germany
2007

Tags: EuroFGI, EuroFGI_MMSOS

Abstract: The evolution of the Internet reveals surprising turns and obstacles. Centralized approaches of introducing new services and architectures consistently failed to materialize at large scale. Quality of Service, group communication, and mobility support are only some examples for the difficulty with orchestrated approaches. The success story of the Internet, on the other hand, is strongly linked to decentralization. Robustness to failures or flexibility in introducing new applications such as the World Wide Web or Peer-to-Peer systems has been key momentum to technological advances and economics. Future networks are envisioned to be highly complex and difficult to manage due to heterogeneity of networks, spontaneous set-up of networks, and the envisioned number of interconnected devices, appliances, and artifacts. The concept of self-organization is widely spread in science among various disciplines. It has been applied successfully already in engineering and for describing the behavior of specific technical systems. Thus, self-organization is foreseen to play a major role in future communication systems.

pdf
Patrick Wuechner, Hermann De Meer, Gunter Bolch, Janos Roszik and Janos Sztrik
Modeling Finite-Source Retrial Queueing Systems with Unreliable Heterogeneous Servers and Different Service Policies Using MOSEL
In Khalid Al-Begain, Armin Heindl and Miklos Telek, editor, Proc. of the 14th Int'l Conf. on Analytical and Stochastic Modelling Techniques and Applications (ASMTA 2007) , page 75--80.
2007
ISBN: 0-9553018-4-X (Print); 0-9553018-3-1 (CD)

Keywords: Performance and Reliability Evaluation; Retrial Queuing System Model; Unreliable Heterogeneous Servers

Tags: DFG_MathMod, EuroFGI, MOSEL2

Abstract: This paper deals with the performance analysis of multiple server retrial queueing systems with a finite number of homogeneous sources of calls, where the heterogeneous servers are subject to random breakdowns and repairs. The requests are serviced according to Random Selection and Fastest Free Server disciplines. The novelty of this investigation is the introduction of different service rates and different service policies together with the unreliability of the servers, which has essential influence on the performance of the system, and thus, it plays an important role in practical modeling of computer and communication systems. All random variables involved in the model construction are assumed to be exponentially distributed and independent of each other. The main steady-state performability measures are derived, and several numerical calculations are carried out by the help of the MOSEL tool (Modeling, Specification and Evaluation Language) under different service disciplines. The numerical results are graphically displayed to illustrate the effect of failure rates on the mean response time and on the overall system utilization.

pdf
Patrick Wuechner, Janos Sztrik and Hermann De Meer
Structured Markov Chains Arising from Homogeneous Finite-Source Retrial Queues with Orbital Search
In Dario Bini, Beatrice Meini, Vaidyanathan Ramaswami, Marie-Ange Remiche and Peter Taylor, editor, Proc. of the Dagstuhl Seminar on Numerical Methods for Structured Markov Chains Volume 07461 of Dagstuhl Seminar Proceedings
Publisher: Schloss Dagstuhl, Leibniz-Zentrum fuer Informatik GmbH, Dagstuhl, Germany
2007

Tags: DFG_MathMod, EuroFGI, EuroFGI_MMSOS, MOSEL2

Abstract: We consider retrial queueing systems with a finite number of homogeneous sources of calls, a single reliable server, and the search for orbiting customers by the server after job completion. During this investigation, the infinitesimal generator of the underlying (finite) continuous-time Markov chain takes a (level-dependent) QBD-like form. After solving for the steady state probabilities using the MOSEL-2 tool, the results show a surprising maximum of the mean response time. This maximum was already discovered by other researchers dealing with finite-source retrial queues. However, to our best knowledge, no thorough investigation was done yet why this maximum exists and in which way it depends on the system parameters. In the talk, after introducing the backgrounds of finite-source retrial queues with orbital search, a generalized stochastic Petri net is used to derive the underlying continuous-time Markov chain and its generator. Finally, using the seminar, we can hopefully bring forward discussions how to make more general statements on the parameter-dependent behavior of the response time's maximum.

2006

Journal articles:

pdf
Hermann De Meer, Patrick Wuechner, Jens B. Schmitt and Matthias Hollick
GI/ITG/MMB/KUVS Fachgespraech Performance Modeling Of Self-Organizing Systems (PMSOS'06)
Praxis der Informationsverarbeitung und Kommunikation (PIK), 29(4):258--262
2006

Tags: EuroFGI, EuroNGI

Abstract: Self-organization is expected to play a key architectural role for the future Internet as well as for large-scale pervasive computing systems such as wireless sensor networks. In conjunction with the ,,International Workshop on Self-Organizing Systems (IWSOS 2006)", we organized the first ,,GI/ITG/MMB/KuVS Fachgespraech on Performance Modeling of Self-Organizing Systems (PMSOS'06)". The event was hosted by the chair of Computer Networks & Communications of Universitaet Passau. To make the Fachgespraech as attractive as possible, we introduced and trialed a novel dialogueintensifying format for discussions. In the aftermaths of the workshop, we have been able to collect evidence that the participants considered the workshop to be very vital and stimulating.

pdf
Patrick Wuechner, Hermann De Meer, Joerg Barner and Gunter Bolch
A brief Introduction to MOSEL-2
Transactions Automated Control Systems, 1:210--214
2006
ISSN: 1512-3979

Tags: EuroFGI, EuroNGI, MOSEL2

Abstract: The versatile MOdeling, Specification and Evaluation Language is the core element of the MOSEL-2 tool. This description languages provides a high-level means for specifying models, performance measures, and the graphical presentation of results. The description languages is implemented in form of an evaluation environment that comprises translators to the modeling languages of several third-party performance evaluation tools that evaluate the specified model.

Conference and workshop papers:

pdf
Patrick Wuechner, Hermann De Meer, Joerg Barner and Gunter Bolch
A brief Introduction to MOSEL-2
In Reinhard German and Armin Heindl, editor, Proc. of the 13th GI/ITG Conf. on Measurement, Modelling and Evaluation of Computer and Communication Systems (MMB 2006) , page 473--476.
GI/ITG/MMB, University of Erlangen
Publisher: VDE Verlag,
2006
ISBN: 978-3-8007-2945-6

Tags: EuroFGI, EuroNGI, MOSEL2

Abstract: The versatile MOdeling, Specification and Evaluation Language is the core element of the MOSEL-2 tool. This description languages provides a high-level means for specifying models, performance measures, and the graphical presentation of results. The description languages is implemented in form of an evaluation environment that comprises translators to the modeling languages of several third-party performance evaluation tools that evaluate the specified model.

pdf
Patrick Wuechner and Hermann De Meer
Discrete-Event System Performance Modeling of Self-Organizing Systems
Proc. of the Technical Discussion on Performance Modeling of Self-Organizing Systems (PMSOS 2006) , page 14--18.
Publisher: University of Passau,
2006

Tags: EPSRC_P2POpt, EuroFGI, EuroNGI

Abstract: The contribution of this paper is twofold. On the one hand the authors give a brief survey on existing publications on the performance modeling of discrete-event systems and on the existing literature on the modeling of self-organizing systems. On the other hand an evaluation is started towards answering the question if modeling techniques designed for discrete-event systems are capable of describing self-organizing systems. We demonstrate that self-organizing systems share many properties of discreteevent systems. Thus, the well-known methods developed for the performance investigation of discrete-event system performance seem to be attractive for the performance evaluation of self-organizing systems.

Note: Technical Report MIP-0609

Technical reports:

pdf
Gunter Bolch, Janos Roszik, Janos Sztrik and Patrick Wuechner
Modeling Finite-Source Retrial Queueing Systems with Unreliable Heterogeneous Servers and Different Service Policies using MOSEL
Document number: MIP-0611
Faculty of Computer Science and Mathematics (FIM), University of Passau,
2006

Tags: DFG_MathMod, EPSRC_P2POpt, EuroFGI, EuroNGI, MOSEL2

Abstract: This paper deals with the performance analysis of multiple server retrial queueing systems with a finite number of homogeneous sources of calls, where the heterogeneous servers are subject to random breakdowns and repairs. The requests are serviced according to Random Selection and Fastest Free Server disciplines. The novelty of this investigation is the introduction of different service rates and different service policies together with the unreliability of the servers, which has essential influence on the performance of the system, and thus it plays an important role in practical modeling of computer and communication systems. All random variables involved in the model construction are assumed to be exponentially distributed and independent of each other. The main steady-state performability measures are derived, and several numerical calculations are carried out by the help of the MOSEL tool (Modeling, Specification and Evaluation Language) under different service disciplines. The numerical results are graphically displayed to illustrate the effect of failure rates on the mean response time and on the overall system's utilization.

pdf
Hermann De Meer, Patrick Wuechner and Amine M. Houyou
Self-Organizing Systems: New Trends in Architectures and Performance Modeling
Document number: MIP-0609
Faculty of Computer Science and Mathematics (FIM), University of Passau,
2006

Tags: EuroFGI, EuroNGI

Abstract: Self-organization plays a key architectural role for the future Internet. Self-organization will enhance flexibility and evolvability of organically growing, large-scale distributed systems, e.g., of large-scale pervasive computing systems such as wireless sensor networks. These statements could be proved by the technical program of the IWSOS 2006. Sixteen high-quality papers were selected by a thorough review process out of more than 70 submissions from 21 different countries. The technical program of the IWSOS 2006 was particularly covering application-oriented topics like: the dynamics of structured and unstructured overlays; self-organization in grids, peer-to-peer networks, wireless environments, and autonomic computing; and the application of self-organization for enhancing network management and routing. The program of the IWSOS 2006 has been supplemented, besides the social events and tutorials, by a poster session on the role of ,,Self-Organization in European Next Generation Internet" and also by a Technical Discussion on ,,Performance Modeling of Self-Organizing Systems". The two parts of the technical report on hand is used to make the contributions to the poster session (Part I) and technical discussion (Part II) available to a broader community.

Note: Supplementary Proc. of IWSOS/PMSOS

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