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Conference on Local Computer Networks (LCN)

作者： Randolf Rotta Navya Sneha Chatharajupalli Billy Naumann Julius Schulz Reinhardt Karnapke Matthias Werner Jörg Nolte Chair of Distributed Systems/Operating Systems BTU Cottbus-Senftenberg Germany Operating Systems Group TU Chemnitz Germany

ISBN: (数字)9798350388008

ISBN: (纸本)9798350388015

When implementing multi-hop mesh network protocols, efficient direct communication, route discovery, and route repair are crucial to achieve high network throughput. To our knowledge, there is no open mesh routing protocol available for ultra low power IEEE 802.11 modules. Previous work relied on single board computers like Raspberry Pi. We implemented the B.A.T.M.A.N. mesh protocol on the popular Espressif ESP32 along with a novel hybrid rate adaptation for the selection of efficient routes. In this demo we showcase challenges and solutions related to the implementation on ESP32 and how the hybrid rate adaptation improves end-to-end throughput.

关键词： Mesh networks Power demand Costs Low power electronics Spread spectrum communication Maintenance engineering Throughput

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B.A.T.M.A.N. Mesh Networking on ESP32’s 802.11

B.A.T.M.A.N. Mesh Networking on ESP32’s 802.11

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Conference on Local Computer Networks (LCN)

作者： Randolf Rotta Julius Schulz Billy Naumann Navya Sneha Chatharajupalli Jörg Nolte Matthias Werner Chair of Distributed Systems/Operating Systems BTU Cottbus-Senftenberg Germany Operating Systems Group TU Chemnitz Germany

ISBN: (数字)9798350388008

ISBN: (纸本)9798350388015

Mesh routing protocols are widely used in IoT and sensor networks. In recent years, the ESP32 Wi-Fi/BLE SoC became popular for prototyping IoT applications. However, the existing mesh networks for this platform lack efficient node to node communication, fast route discovery and repair, and energy efficiency. This paper addresses the formation of IEEE 802.11 based ad-hoc mesh networks without the delays inflicted by the Station to Access Point association protocol. We implemented the B.A.T.M.A.N. protocol on top of the ESP32 Wi-Fi MAC interface and integrated it into the LwIP network stack. The performance evaluation with respect to UDP/IP and TCP/IP end-to-end throughput shows the general usefulness but also identifies bottlenecks caused by limitations of the existing MAC interface. Overall, this opens an interesting opportunity for research on mesh protocols by providing a simpler platform than full featured Wi-Fi routers; and for wireless IoT applications by providing higher throughput than subGHz and BLE technologies.

关键词： Wireless communication Performance evaluation Mesh networks Wireless sensor networks TCPIP Throughput Routing protocols

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From Intent to Effect: Tool-Based Generation of Time-Triggered Real-Time systems on Multi-core Processors

From Intent to Effect: Tool-Based Generation of Time-Trigger...

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International Symposium on Object-Oriented Real-Time distributed Computing

作者： Florian Franzmann Tobias Klaus Peter Ulbrich Patrick Deinhardt Benjamin Steffes Fabian Scheler Wolfgang Schröder-Preikschat Chair of Distributed Systems and Operating Systems Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Germany Process Industries and Drives Nuremberg Germany

Although the manual creation of time-triggered schedules for multi-core real-time systems can be a daunting task, state-of-the-art scheduling algorithms are far from being widely used. This suggests that the availability of sound algorithms is only one side of the story: real-time systems have to be groomed substantially before they can serve as input to available algorithms. Moreover, systems engineers struggle with the temporal effects of their design decisions, in addition to the intended timing properties. Therefore, we believe that appropriate tools are the other side of the story. In this paper, we present the multicore extension of the Real-Time systems Compiler, a compiler-based tool that analyses given event-triggered real-time systems and transforms them into time-triggered equivalents. We focus on the challenges and pitfalls in the transition from theory to practical implementation and present concrete solutions to resolve them. Existing algorithms need to be adapted for performance and, at model level, bound together appropriately to be applicable, for example. Our experiments substantiate the effectiveness and scalability of our approach, even for large tasks sets. Finally, lessons learned give an insight into implementation and hardware details and their impact on schedulability.

关键词： Real-time systems Schedules Software Safety Algorithm design and analysis Hardware Job shop scheduling

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Closing the loop: towards control-aware design of adaptive real-time systems

Closing the loop: towards control-aware design of adaptive r...

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Real-Time systems Symposium (RTSS)

作者： Tobias Klaus Florian Franzmann Maximilian Gaukler Andreas Michalka Peter Ulbrich Chair of Distributed Systems and Operating Systems Germany Lehrstuhl für Regelungstechnik (Chair of Automatic Control) Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Germany

This paper proposes a continuous toolchain from the original control system model to the resulting schedules. As a first step towards control-aware yet adaptive system design, we focused on a global, context-sensitive analysis of control and data flow across control-application layers and threads of execution. This step is of vital importance as these dependencies manifest differently on the various levels of abstraction. Consequently, we extract semantics and internal dependencies directly from control-system models by an extended version of the Real-Time systems Compiler (RTSC), which is capable of analyzing and transforming real-time applications on the source code level.

关键词： Real-time systems Delays Adaptive systems Time factors Switches

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Internet: A certain insecurity

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Network Security 1995年第9期1995卷 16-19页

作者： Bob Herschberg Edo Roos Lindgreen Delft University of Technology The Netherlands Professor in the chair of Operating Systems and Distributed Systems at Delft University of Technology The Netherlands Ph. D. student at Delft University of Technology The Netherlands

Despite the rapidly increasing popularity of the Internet, many still view this new communication system as a fad that will pass as quickly as it has emerged. In many cases, management defers investments in Internet technology and skills until mañana and a day. Who can blame them? Three decades of experience with the information-technology industry have taught these managers that the economic lifespan of its products and companies is insanely short, and that caution is a successful strategy to avoid irresponsible investments. However, as caution degrades into neglect, management degrades into dismissing new products and services without thoroughly vetting them.

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A Practitioner's Guide to Software-Based Soft-Error Mitigation Using AN-Codes

A Practitioner's Guide to Software-Based Soft-Error Mitigati...

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IEEE International Symposim on High Assurance systems Engineering

作者： Martin Hoffmann Peter Ulbrich Christian Dietrich Horst Schirmeier Daniel Lohmann Wolfgang Schröder-Preikschat Chair of Distributed Systems and Operating Systems Friedrich-Alexander University Erlangen-Nuremberg Germany Department of Computer Science 12 Technische Universität Dortmund Germany

Arithmetic error coding schemes (AN codes) are a well known and effective technique for soft error mitigation. Although coding theory being a rich area of mathematics, their implementation seems to be fairly easy. However, compliance with the theory can be lost easily while moving towards an actual implementation - finally jeopardizing the aspired fault-tolerance characteristics. In this paper, we present our experiences and lessons learned from implementing AN codes in the Cored dependable voter. We focus on the challenges and pitfalls in the transition from maths to machine code for a binary computer from a systems perspective. Our results show, that practical misconceptions (such as the use of prime numbers) and architecture-dependent implementation glitches occur on every stage of this transition. We identify typical pitfalls and describe practical measures to find and resolve them. Our measures eliminate all remaining SDCs in the Cored voter, which is validated by an extensive fault-injection campaign that covers 100 percent of the fault space for 1-bit and 2-bit errors.

关键词： Encoding Error probability Registers Hardware Fault tolerance

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FAIL*: An Open and Versatile Fault-Injection Framework for the Assessment of Software-Implemented Hardware Fault Tolerance

FAIL*: An Open and Versatile Fault-Injection Framework for t...

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European Dependable Computing Conference (EDCC)

作者： Horst Schirmeier Martin Hoffmann Christian Dietrich Michael Lenz Daniel Lohmann Olaf Spinczyk Departmcnt of Computer Science 12 Technische Universität Dortmund Germany Chair of Distributed Systems and Operating Systems Friedrich-Alexander-Universitat Erlangen-Ntirnberg Germany

ISBN: (纸本)9781467392907

Due to voltage and structure shrinking, the influence of radiation on a circuit's operation increases, resulting in future hardware designs exhibiting much higher rates of soft errors. Software developers have to cope with these effects to ensure functional safety. However, software-based hardware fault tolerance is a holistic property that is tricky to achieve in practice, potentially impaired by every single design decision. We present FAIL*, an open and versatile architecture-level fault-injection (FI) framework for the continuous assessment and quantification of fault tolerance in an iterative software development process. FAIL* supplies the developer with reusable and composable FI campaigns, advanced pre-and post-processing analyses to easily identify sensitive spots in the software, well-abstracted back-end implementations for several hardware and simulator platforms, and scalability of FI campaigns by providing massive parallelization. We describe FAIL*, its application to the development process of safety-critical software, and the lessons learned from a real-world example.

关键词： Hardware Software Circuit faults Fault tolerance Fault tolerant systems Computer architecture Software measurement

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An Optical Transceiver Reliability Study based on SFP Monitoring and OS-level Metric Data

An Optical Transceiver Reliability Study based on SFP Monito...

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IEEE/ACM International Symposium on Cluster Computing and the Grid (CCGRID)

作者： Paolo Notaro Qiao Yu Soroush Haeri Jorge Cardoso Michael Gerndt Huawei Technologies Duesseldorf GmbH Munich Germany Chair of Computer Architecture and Parallel Systems Technical University of Munich Germany Chair of Distributed and Operating Systems Technical University of Berlin Germany Department of Informatics Engineering/CISUC University of Coimbra Portugal

The increasing demand for cloud computing drives the expansion in scale of datacenters and their internal optical network, in a strive for increasing bandwidth, high reliability, and lower latency. Optical transceivers are essential elements of optical networks, whose reliability has not been well-studied compared to other hardware components. In this paper, we leverage high quantities of monitoring data from optical transceivers and OS-level metrics to provide statistical insights about the occurrence of optical transceiver failures. We estimate transceiver failure rates and normal operating ranges for monitored attributes, correlate early-observable patterns to known failure symptoms, and finally develop failure prediction models based on our analyses. Our results enable network administrators to deploy early-warning systems and enact predictive maintenance strategies, such as replacement or traffic re-routing, reducing the number of incidents and their associated costs.

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Taking control: Modular and adaptive robotics process control systems

Taking control: Modular and adaptive robotics process contro...

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International Workshop on Robot Sensing (ROSE)

作者： Peter Ulbrich Florian Franzmann Christian Harkort Martin Hoffmann Tobias Klaus Anja Rebhan Wolfgang Schröder-Preikschat Chair of Distributed Systems and Operating Systems Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Germany Chair of Automatic Control Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Germany Friedrich-Alexander-Universitat Erlangen-Nurnberg Erlangen Bayern DE

Robotics systems usually comprise sophisticated sensor and actuator systems with no less complex control applications. These systems are subject to frequent modifications and extensions and have to adapt to their environment. While automation systems are tailored to particular production processes, autonomous vehicles must adaptively switch their sensors and controllers depending on environmental conditions. However, when designing and implementing the process control system, traditional control theory focuses on the control problem at hand without having this variability in mind. Thus, the resulting models and implementation artefacts are monolithic, additionally complicating the real-time system design. In this paper, we present a modularisation approach for the design of robotics process control systems, which not only aims for variability at design-time but also for adaptivity at run-time. Our approach is based on a layered control architecture, which includes an explicit interface between the two domains involved: control engineering and computer science. Our architecture provides separation of concerns in terms of independent building blocks and data flows. For example, the replacement of a sensor no longer involves the tedious modification of downstream filters and controllers. Likewise, the error-prone mapping of high-level application behaviour to the process control system can be omitted. We validated our approach by the example of an autonomous vehicle use case. Our experimental results demonstrate ease of use and the capability to maintain quality of control on par with the original monolithic design.

关键词： Observers Sensor fusion Actuators Sensor systems Real-time systems

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A brief Introduction to MOSEL-2

A brief Introduction to MOSEL-2

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13th GI/ITG Conference - Measuring, Modelling and Evaluation of Computer and Communication systems

作者： Patrick Wuechner Hermann de Meer Joerg Barner Gunter Bolch Chair of Computer Networks and Computer Communications Faculty of Mathematics and Computer Science University of Passau Innstr. 33 94032 Passau Germany Research Group on Analytical Modeling Chair of Distributed Systems and Operating Systems Department of Computer Science University of Erlangen-Nürnberg Martensstr. 1 91058 Germany

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.

关键词： Numerical models Computational modeling Stochastic processes Mathematical model Analytical models Computer performance Performance evaluation

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