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IEEE International Conference on Communications

作者： Steffen Bondorf Distributed Computer Systems (DISCO) Lab University of Kaiserslautern Germany

Safety-critical systems require certification in order to attain permission to operate. Nowadays, these systems routinely embed a communication sub-systems whose performance must be formally verified for certification. Deterministic Network Calculus (DNC) can be employed for this task. It provides a mathematical framework to derive worst-case bounds on the delay of data flows, i.e., deterministic delivery guarantees. Their accuracy is decisive as even small improvements can change the outcome of certification. In general, delay bound accuracy depends on the accuracy of the network model. While previous work assumed that a more accurate model will invariantly yield more accurate delay bounds, we show that the opposite can actually be true. In this paper, we examine a specific weakness of DNC network analysis that leads to this counter-intuitive result. We make use of this insight in a mitigation strategy called flow prolongation. By prolonging the paths of flows, we let them interfere with more other flows but may still get better results. An evaluation in differently sized networks gives information about its impact on delay bound accuracy as well as analysis effort.

关键词： Delays Servers Multiplexing Calculus Interference Aggregates Mathematical model

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What do biodiversity scholars search for? Identifying high-level entities for biological metadata 2

What do biodiversity scholars search for? Identifying high-l...

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2nd International Workshop on Semantics for Biodiversity, S4BioDiv 2017

作者： Löffler, Felicitas Pfaff, Claas-Thido Karam, Naouel Fichtmüller, David Klan, Friederike Heinz-Nixdorf Endowed Departmentt for Distributed Information Systems FSU Jena Germany Systematic Botany and Functional Biodiversity Lab. University of Leipzig Germany Institute of Computer Science Freie Universität Berlin Germany Freie Universität Berlin Germany

Research questions in biodiversity are as diverse and heterogeneous as data are. Most metadata standards are mainly data-focused and pay little attention to the search perspective. In this work, we introduce a method to analyze the actual information need of biodiversity scholars based on two individual studies: (1) a series of workshops with domain experts and (2) an analysis of research and search questions collected in three different biodiversity projects. We finally present 12 high-level entities that appear in all kinds of biological data across the different sources evaluated.

关键词： Biodiversity

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Towards the analysis of transient phases with stochastic network calculus

Towards the analysis of transient phases with stochastic net...

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NETWORKS International Telecommunications Network Strategy and Planning Symposium

作者： Michael Beck University of Kaiserslautern Germany Distributed Computer Systems Lab (DISCO)

ISBN: (纸本)9781467389921

Current analysis methods for queueing systems mostly aim at steady-state results. However, many applications demand results for systems with a transient behavior. In communication networks such transient phases arise from sleep scheduling or the slow-start phase of TCP. In both examples the service offered is separated into a transient and a steady-state phase. In a larger context also the arrivals to a queueing system can show transient behavior. The demand or availab.lity of energy in smart grids, the pool of data generated after the map phase in big data applications, or the arrivals in public transportation networks are a few examples. Analyzing these kind of systems in a steady-state fashion (for example via queueing theory) ignores their behavior in the transient phases. On the other side the analysis of transient phases bears additional challenges. This paper uses stochastic network calculus to describe the non-stationary behavior of queueing systems. With the help of bivariate arrival- and service envelopes time-variant performance bounds are constructed. Two numerical examples exemplify the framework created by these envelopes and compare it to the time-invariant analysis.

关键词： Transient analysis Queueing analysis Steady-state Calculus Stochastic processes Delays Mathematical model

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Solution of Traveling Salesman Problem with Hotel Selection in the framework of MILP-tropical optimization

Solution of Traveling Salesman Problem with Hotel Selection ...

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American Control Conference

作者： Mohammadreza Radmanesh Manish Kumar Alireza Nemati Mohammad Sarim Cooperative Distributed Systems Lab. Department of Mechanical and Materials Engineering University of Cincinnati Ohio 45221 USA Department of Mechanical and Materials Engineering University of Cincinnati Ohio 45221 USA Cooperative Distributed Systems Lab. Department of Electrical Engineering and Computer Science University of Cincinnati Ohio 45221 USA

ISBN: (纸本)9781467386838

In this paper, Traveling Salesman Problem with Hotel Selection (TSPHS), an extension of the Traveling Salesman Problem (TSP) has been considered. A mathematical formulation has been presented in the framework of Mixed Integer Linear Programming (MILP). Subsequently, the problem has been formulated in the novel framework of tropical mathematics and a strategy to obtain exact solution has been proposed. The performance of the proposed solution, in terms of the optimality and computational time requirement, has been compared with the solution strategies availab.e in literature including traditional MILP. The results indicate that the proposed solution strategy not only leads to optimal results but also is computationally much more efficient.

关键词： Traveling salesman problems Linear programming Optimization Urban areas Vehicles Routing

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Boosting sensor network calculus by thoroughly bounding cross-traffic

Boosting sensor network calculus by thoroughly bounding cros...

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IEEE Annual Joint Conference: INFOCOM, IEEE computer and Communications Societies

作者： Steffen Bondorf Jens B. Schmitt Distributed Computer Systems (DISCO) Lab University of Kaiserslautern Germany

Sensor Network Calculus (SensorNC) provides a framework for worst-case analysis of wireless sensor networks. The analysis proceeds in two steps: For a given flow, (1) the network is reduced to a tandem of nodes by computing the arrival bounds of cross-traffic; (2) the flow is separated from the cross-traffic by subtracting cross-flows and concatenating nodes on its path. While the second step has seen much treatment, the first step has not at all. This is in sharp contrast to the fact that arrival bounding takes roughly 80% of the total analysis time and is equally crucial for the tightness of the bounds. Therefore, we turn our attention to this first SensorNC analysis step with the goal to boost the performance and applicability of the overall framework. The main technical contribution is a generalized version of the concatenation theorem within the SensorNC setting. This generalization is instrumental in simplifying and streamlining the cross-traffic arrival bound computations such that run times can be reduced by more than a factor of 5. Even more important, it enables a localization of the information necessary to execute the calculations at the node level, thus enabling a distribution of the SensorNC analysis within a self-modeling WSN.

关键词： Calculus Servers Delays Aggregates Wireless sensor networks Topology computers

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Towards a Statistical Network Calculus-Dealing with Uncertainty in Arrivals

Towards a Statistical Network Calculus-Dealing with Uncertai...

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IEEE International Conference on computer Communications

作者： Michael A. Beck Sebastian A. Henningsen Simon B. Birnbach Jens B. Schmitt Distributed Computer Systems (DISCO) Lab University of Kaiserslautern Germany

The stochastic network calculus (SNC) has become an attractive methodology to derive probabilistic performance bounds. So far the SNC is based on (tacitly assumed) exact probabilistic assumptions about the arrival processes. Yet, in practice, these are only true approximately-at best. In many situations it is hard, if possible at all, to make such assumptions a priori. A more practical approach would be to base the SNC operations on measurements of the arrival processes (preferably even on-line). In this paper, we develop this idea and incorporate measurements into the framework of SNC taking the further uncertainty resulting from estimation errors into account. This is a crucial step towards a statistical network calculus (StatNC) eventually lending itself to a self-modelling operation of networks with a minimum of a priori assumptions. In numerical experiments, we are able to substantiate the novel opportunities by StatNC.

关键词： Calculus Probabilistic logic Uncertainty computers Stochastic processes Conferences Random variables

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Semantic self-management and mediation for home service platforms 44

Semantic self-management and mediation for home service plat...

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44. Jahrestagung der Gesellschaft fur Informatik INFORMATIK 2014 - Big Data - Komplexitat meistern - Big Data - Mastering Complexity: 44th Annual Meeting of the Society for computer Science, INFORMATICS 2014

作者： Schaefer, Jan RheinMain University of Applied Sciences Design Computer Science Media Department Distributed Systems Lab. Unter den Eichen 5 WiesbadenD-65195 Germany

ISBN: (纸本)9783885796268

Service-oriented computing has long outgrown the enterprise. Today, personal livingenvironments feature an increasing number of convenience-, health-and securityrelatedapplications provided by distributed interacting devices and services (oftencalled smart homes), which do not only support users but require management taskssuch as application installation, configuration and continuous maintenance. Thesetasks are becoming complex and error-prone. One way to escape this situation is toenable service platforms to configure and manage themselves. The approach presentedhere extends services with semantic descriptions to enable platform-independent autonomousservice level management and mediation using model driven architectureand autonomic computing concepts. It has been implemented as a semantic autonomicmanager, whose concept, prototypical implementation and evaluation are presented.

关键词： Smart homes

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A control approach for performance of big data systems 19

A control approach for performance of big data systems

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19th IFAC World Congress on International Federation of Automatic Control, IFAC 2014

作者： Berekmeri, M. Serrano, D. Bouchenak, S. Marchand, N. Robu, B. GIPSA-Lab. BP 46 Grenoble38402 France Distributed Computer Systems Group LIG BP 53 Grenoble38402 France CNRS France Univ. Grenoble Alpes GrenobleF-38402 France

ISBN: (纸本)9783902823625

We are at the dawn of a huge data explosion therefore companies have fast growing amounts of data to process. For this purpose Google developed MapReduce, a parallel programming paradigm which is slowly becoming the de facto tool for Big Data analytics. Although to some extent its use is already wide-spread in the industry, ensuring performance constraints for such a complex system poses great challenges and its management requires a high level of expertise. This paper answers these challenges by providing the first autonomous controller that ensures service time constraints of a concurrent MapReduce workload. We develop the first dynamic model of a MapReduce cluster. Furthermore, PI feedback control is developed and implemented to ensure service time constraints. A feedforward controller is added to improve control response in the presence of disturbances, namely changes in the number of clients. The approach is validated online on a real 40 node MapReduce cluster, running a data intensive Business Intelligence workload. Our experiments demonstrate that the designed control is successful in assuring service time constraints. © IFAC.

关键词： Big data

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Inside risks: Keys under doormats

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Communications of the ACM 2015年第10期58卷 24-26页

作者： Abelson, Harold Anderson, Ross Bellovin, Steven M. Benaloh, Josh Blaze, Matt Diffie, Whitfield Gilmore, John Green, Matthew Landau, Susan Neumann, Peter G. Rivest, Ronald L. Schiller, Jeffrey I. Schneier, Bruce Specter, Michael A. Weitzner, Daniel J. MIT Creative Commons Free Software Foundation United States University of Cambridge United Kingdom Computer Science Columbia University United States Microsoft Research United States University of Pennsylvania Distributed Systems Lab. United States Internet-Scale Communications United States Sun Microsystems Cygnus Solutions Electronic Frontier Foundation Cypherpunks Internet's alt newsgroups United States Johns Hopkins University Information Security Institute United States Worcester Polytechnic Institute United States Computer Science Lab SRI International ACM Risks Forum United States MIT Institute RSA Security and Verisign United States Internet Engineering Steering Group United States Berkman Center for Internet and Society Harvard Law School Resilient Systems Inc United States MIT Computer Science and Artificial Intelligence Lab MIT Cybersecurity and Internet Policy Research Initiative United States

The complexity of today's Internet environment means new law enforcement requirements are likely to introduce unanticipated security flaws. Political and law enforcement leaders in the U.S. and the U.K. have called for Internet systems to be redesigned to ensure government access to information even encrypted information. There are three general problems. First, providing exceptional access to communications would force a U-turn from the best practices now being deployed to make the Internet more secure. These practices include forward secrecy, where decryption keys are deleted immediately after use, so that stealing the encryption key used by a communications server would not compromise earlier or later communications. Second, building in exceptional access would substantially increase system complexity. Third, exceptional access would create concentrated targets that could attract bad actors. Moreover, law enforcement's stated need for rapid access to data would make it impractical to store keys offline or split keys among multiple key holders, as security engineers would normally do with extremely high-value credentials.

关键词： Law enforcement

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Towards measurement-based self-management of performance properties in wireless sensor networks

Towards measurement-based self-management of performance pro...

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10th ACM International Symposium on Performance Evaluation of Wireless Ad Hoc, Sensor, and Ubiquitous Networks, PE-WASUN 2013 - Co-located with ACM MSWiM 2013

作者： Bachorek, Adam Palanisamy, Bagavathiannan Schmitt, Jens B. Disco / Distributed Computer Systems Lab. University of Kaiserslautern Kaiserslautern Germany

ISBN: (纸本)9781450323604

Ensuring the aspired outcome quality of network-based applications has ever implied an appropriate prognosis of the performance behavior the underlying communication structures will exhibit prior to potential optimization steps. However, the reliable forecast of correlative metrics is still a challenging task, especially in terms of wireless network systems that reject centralized or manual administration. In the context of our prospective self-management concept for autonomous analysis and control of volatile performance characteristics in Wireless Sensor Networks (WSNs), we relate a common network property known as packet transfer delay to various adjustable parameters peculiar to such radio network technologies. Our hands-on experiments reveal the reproducible influence of packet size, backoff period, and number of active neighbor nodes on the medium access procedure and involved performance indicators. By means of a closed formulation of permutable weighted drivers, we investigate the average-case predictability of inter-node end-to-end delays for arbitrary configurations of given network parameters. We validate our prediction method against basic multi-hop networking scenarios while verifying its practicability on a typical resource-scarce WSN platform. Leveraging measurement-driven inspection and conditional modeling of network attributes based on regression analysis, yield field test results substantiate the high precision of our approach to the estimation of performance-related WSN properties as the basis for application-aware performance optimization subject to projected complements. © 2013 ACM.

关键词： Forecasting

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