Body Condition and Productivity, Health and Welfare

This reprint focuses on applied research on growth traits, fat reserves, fatty acid profiles and enriched diets and their effects on reproduction, health status and welfare. The studies contained in the volume have been carried out in both monogastric organisms and ruminants, fish, broilers or pigeons. Fundamental studies with rats or mice are also presented. The reader will find novel research about the effects of the degree of fatness and muscularity determined by ultrasound method on sows´ reproductive performance, genetic studies on fatty acid profiles and growth traits in rabbits and Gilthead Seabream; nutritional studies addressing diets enriched with bee pollen in rats, postbiotics in male rabbits, concentrate and bypass supplementations in buffaloes; and interesting studies on the welfare assessment of meat sheep, rabbits, racing pigeons, broilers, alpacas and llamas using body condition measurements

The Signal Synchronous Multiclock Approach to the Design of Distributed Embedded System

International audienceThis paper presents the design of distributed embedded systems using the synchronous multiclock model of the Signal language. It proposes a methodology that ensures a correct-by-construction functional implementation of these systems from high-level models. It shows the capability of the synchronous approach to apply formal techniques and tools that guarantee the reliability of the designed systems. Such a capability is necessary and highly worthy when dealing with safety-critical systems. The proposed methodology is demonstrated through a case study consisting of a simple avionic application, which aims to pragmatically help the reader to understand the manipulated formal concepts, and to apply them easily in order to solve system correctness issues encountered in practice. The application functionality is first modeled as well as its distribution on a generic hardware architecture. This relies on the endochrony and endo-isochrony properties of Signal specifications, defined previously. The considered architectures include asynchronous communication mechanisms, which are also modeled in Signal and proved to achieve message exchanges correctly. Furthermore, the synchronizability of the different parts in the resulting system is addressed after its deployment on a specific execution platform with multirate clocks. After all these steps, a distributed code can be automatically generated

Spatiotemporal Multicast and Partitionable Group Membership Service

The recent advent of wireless mobile ad hoc networks and sensor networks creates many opportunities and challenges. This thesis explores some of them. In light of new application requirements in such environments, it proposes a new multicast paradigm called spatiotemporal multicast for supporting ad hoc network applications which require both spatial and temporal coordination. With a focus on a special case of spatiotemporal multicast, called mobicast, this work proposes several novel protocols and analyzes their performances. This dissertation also investigates implications of mobility on the classical group membership problem in distributed computing, proposes a new specification for a partitionable group membership service catering to applications on wireless mobile ad hoc networks, and provides a mobility-aware algorithm and middleware for this service. The results of this work bring new insights into the design and analysis of spatiotemporal communication protocols and fault-tolerant computing in wireless mobile ad hoc networks

Fault-tolerant and transactional mobile agent execution

Mobile agents constitute a computing paradigm of a more general nature than the widely used client/server computing paradigm. A mobile agent is essentially a computer program that acts autonomously on behalf of a user and travels through a network of heterogeneous machines. However, the greater flexibility of the mobile agent paradigm compared to the client/server computing paradigm comes at additional costs. These costs include, among others, the additional complexity of developing and managing mobile agent-based applications. This additional complexity comprises such issues as reliability. Before mobile agent technology can appear at the core of tomorrow's business applications, reliability mechanisms for mobile agents must be established. In this context, fault tolerance and transaction support are mechanisms of considerable importance. Various approaches to fault tolerance and transaction support exist. They have different strengths and weaknesses, and address different environments. Because of this variety, it is often difficult for the application programmer to choose the approach best suited to an application. This thesis introduces a classification of current approaches to fault-tolerant and transactional mobile agent execution. The classification, which focuses on algorithmic aspects, aims at structuring the field of fault-tolerant and transactional mobile agent execution and facilitates an understanding of the properties and weaknesses of particular approaches. In a distributed system, any software or hardware component may be subject to failures. A single failing component (e.g., agent or machine) may prevent the agent from proceeding with its execution. Worse yet, the current state of the agent and even its code may be lost. We say that the agent execution is blocked. For the agent owner, i.e., the person or application that has configured the agent, the agent does not return. To achieve fault-tolerance, the agent owner can try to detect the failure of the agent, and upon such an event launch a new agent. However, this requires the ability to correctly detect the crash of the agent, i.e., to distinguish between a failed agent and an agent that is delayed by slow processors or slow communication links. Unfortunately, this cannot be achieved in systems such as the Internet. An agent owner who tries to detect the failure of the agent thus cannot prevent the case in which the agent is mistakenly assumed to have crashed. In this case, launching a new agent leads to multiple executions of the agent, i.e., to the violation of the desired exactly-once property of agent execution. Although this may be acceptable for certain applications (e.g., applications whose operations do not have side-effects), others clearly forbid it. In this context, launching a new agent is a form of replication. In general, replication prevents blocking, but may lead to multiple executions of the agent, i.e., to a violation of the exactly-once execution property. This thesis presents an approach that ensures the exactly-once execution property using a simple principle: the mobile agent execution is modeled as a sequence of agreement problems. This model leads to an approach based on two well-known building blocks: consensus and reliable broadcast. We validate this approach with the implementation of FATOMAS, a Java-based FAult-TOlerant Mobile Agent System, and measure its overhead. Transactional mobile agents execute the mobile agent as a transaction. Assume, for instance, an agent whose task is to buy an airline ticket, book a hotel room, and rent a car at the flight destination. The agent owner naturally wants all three operations to succeed or none at all. Clearly, the rental car at the destination is of no use if no flight to the destination is available. On the other hand, the airline ticket may be useless if no rental car is available. The mobile agent's operations thus need to execute atomically, i.e., either all of them or none at all. Execution atomicity also needs to be ensured in the event of failures of hardware or software components. The approach presented in this thesis is non-blocking. A non-blocking transactional mobile agent execution has the important advantage that it can make progress despite failures. In a blocking transactional mobile agent execution, by contrast, progress is only possible when the failed component has recovered. Until then, the acquired locks generally cannot be freed. As no other transactional mobile agents can acquire the lock, overall system throughput is dramatically reduced. The present approach reuses the work on fault-tolerant mobile agent execution to prevent blocking. We have implemented the proposed approach and present the evaluation results

Evaluating the performance of distributed agreement algorithms:tools, methodology and case studies

Nowadays, networked computers are present in most aspects of everyday life. Moreover, essential parts of society come to depend on distributed systems formed of networked computers, thus making such systems secure and fault tolerant is a top priority. If the particular fault tolerance requirement is high availability, replication of components is a natural choice. Replication is a difficult problem as the state of the replicas must be kept consistent even if some replicas fail, and because in distributed systems, relying on centralized control or a certain timing behavior is often not feasible. Replication in distributed systems is often implemented using group communication. Group communication is concerned with providing high-level multipoint communication primitives and the associated tools. Most often, an emphasis is put on tolerating crash failures of processes. At the heart of most communication primitives lies an agreement problem: the members of a group must agree on things like the set of messages to be delivered to the application, the delivery order of messages, or the set of processes that crashed. A lot of algorithms to solve agreement problems have been proposed and their correctness proven. However, performance aspects of agreement algorithms have been somewhat neglected, for a variety of reasons: the lack of theoretical and practical tools to help performance evaluation, and the lack of well-defined benchmarks for agreement algorithms. Also, most performance studies focus on analyzing failure free runs only. In our view, the limited understanding of performance aspects, in both failure free scenarios and scenarios with failure handling, is an obstacle for adopting agreement protocols in practice, and is part of the explanation why such protocols are not in widespread use in the industry today. The main goal of this thesis is to advance the state of the art in this field. The thesis has major contributions in three domains: new tools, methodology and performance studies. As for new tools, a simulation and prototyping framework offers a practical tool, and some new complexity metrics a theoretical tool for the performance evaluation of agreement algorithms. As for methodology, the thesis proposes a set of well-defined benchmarks for atomic broadcast algorithms (such algorithms are important as they provide the basis for a number of replication techniques). Finally, three studies are presented that investigate important performance issues with agreement algorithms. The prototyping and simulation framework simplifies the tedious task of developing algorithms based on message passing, the communication model that most agreement algorithms are written for. In this framework, the same implementation can be reused for simulations and performance measurements on a real network. This characteristic greatly eases the task of validating simulation results with measurements (or vice versa). As for theoretical tools, we introduce two complexity metrics that predict performance with more accuracy than the traditional time and message complexity metrics. The key point is that our metrics take account for resource contention, both on the network and the hosts; resource contention is widely recognized as having a major impact on the performance of distributed algorithms. Extensive validation studies have been conducted. Currently, no widely accepted benchmarks exist for agreement algorithms or group communication toolkits, which makes comparing performance results from different sources difficult. In an attempt to consolidate the situation, we define a number of benchmarks for atomic broadcast. Our benchmarks include well-defined metrics, workloads and failure scenarios (faultloads). The use of the benchmarks is illustrated in two detailed case studies. Two widespread mechanisms for handling failures are unreliable failure detectors which provide inconsistent information about failures, and a group membership service which provides consistent information about failures, respectively. We analyze the performance tradeoffs of these two techniques, by comparing the performance of two atomic broadcast algorithms designed for an asynchronous system. Based on our results, we advocate a combined use of the two approaches to failure handling. In another case study, we compare two consensus algorithms designed for an asynchronous system. The two algorithms differ in how they coordinate the decision process: the one uses a centralized and the other a decentralized communication schema. Our results show that the performance tradeoffs are highly affected by a number of characteristics of the environment, like the availability of multicast and the amount of contention on the hosts versus the amount of contention on the network. Famous theoretical results state that a lot of important agreement problems are not solvable in the asynchronous system model. In our third case study, we investigate how these results are relevant for implementations of a replicated service, by conducting an experiment in a local area network. We exposed a replicated server to extremely high loads and required that the underlying failure detection service detects crashes very fast; the latter is important as the theoretical results are based on the impossibility of reliable failure detection. We found that our replicated server continued working even with the most extreme settings. We discuss the reasons for the robustness of our replicated server

I-Centric Communications

Diese Arbeit beschreibt die Vision I-centric Communications ein neues Paradigma für zukünftige Telekommunikationssysteme. Das Hauptziel dieses Ansatzes ist es das menschliche Kommunikationsverhalten und nicht die Technologien die typischerweise zur Kommunikation eingesetzt werden, als Ausgangsbasis für den Entwurf von Telekommunikationssystemen zu benutzen. Daher konzentriert sich diese Arbeit auf die konzeptionelle Integration aller für I-centric Communications notwendigen Aspekte. Untersucht man das Kommunikationsverhalten von Menschen näher, wird klar, dass Menschen regelmäßig mit einer bestimmten Menge von Objekten in ihrer Umgebung interagieren um ihre täglichen Probleme zu lösen. Diese Erkenntnis kann als Grundlage für den Entwurf von Telekommunikationssystemen dienen. Der Entwurf stützt sich dabei nicht auf spezifische Telekommunikationstechnologien sondern auf die Analyse individueller Kommunikationsräume. Das Resultat eines solchen Entwurfs ist ein Telekommunikationssystem, dass sich an die individuellen Anforderungen eines jeden Menschen anpasst (I-centric). Das Kommunikationssystem agiert im Sinne des Benutzers, protokolliert wiederkehrende Aktionen, um sich selbst den Bedürfnissen des Benutzers weiter anzupassen. Die beschriebene Funktionalität erfordert eine intelligente Diensterbringung im Hinblick auf die Personalisierung von Diensten, der Adaption an situationsbedingte oder umgebungsabhängige Einflüsse, und der Überwachung bzw. Steuerung von individuellen Kommunikationsräumen. Kommunikationssysteme die dieser Idee folgen müssen individuelle Kommunikationsräume modellieren und verwalten um sich an die persönlichen Interessen, Umgebungen und Präferenzen anpassen zu können. Diese Arbeit beginnt mit der Vorstellung der Vision I-centric Communications , gefolgt von der Entwicklung eines entsprechenden Referenzmodells. Im Anschluss wird auf der Basis des Referenzmodells eine Architektur zur Implementierung von I-centric Kommunikationssystemen entwickelt. Die Vorstellung einer der Architektur folgenden Implementierung schließt diese Arbeit ab. Die Forschungsarbeit im Bereich I-centric Communications wurde in Kooperation zwischen dem Lehrstuhl für Offene Kommunikationssysteme (OKS) der Technischen Universität Berlin (TUB) und dem Fraunhofer Institut FOKUS durchgeführt. Die Vision sowie das Referenzmodell für I-centric Communications , die in der vorliegenden Arbeit vorgestellt werden, sind Ergebnisse dieser Kooperation. Die Forschungsschwerpunkte der Kooperation zwischen TUB und FOKUS waren das Generelle Modell für I-centric Dienste , die Dienstplattform für I-centric Dienste sowie die Interaktion zwischen Nutzern und I-centric Diensten . Die vorliegende Arbeit konzentriert sich auf das generische Model für I-centric Dienste und entsprechende Dienstplattformen. Aspekte der individuellen Benutzerinteraktion werden nicht betrachtet. Diese Aspekte wurden in einer zweiten Dissertation von Stephan Steglich, TUB, analysiert und ausgearbeitet. Die Ergebnisse dieser Dissertation wurden in verschiedenen nationalen und internationalen Forschungsprojekten (BMBF: LiveFutura, VHE-UD, PI-AVIda, IST: WSI, WWRI), Standardisierungsgremien (OMG, WWRF), Konferenzpapieren sowie Zeitschriften eingebracht, um die Vision von I-centric Communications einem größeren Auditorium vorzustellen.This thesis describes the vision of I-centric communications a new paradigm for future telecommunication systems. The main objective of this approach is to consider the human communication behavior, not the technologies that support communication, as the starting point for the design of telecommunication systems. The focus of this thesis is on the conceptual integration of all aspects of I-centric communications. Looking at the communication behavior of human, it is obvious, that human beings frequently interact with a set of objects in their environment. Following this view, a new approach is not to build communication systems based on specific technologies, but on the analysis of the individual communication space. The result is a communication system that adapts to the demands of each individual (I-centric). The communication system will act on behalf of human s demands, reflecting recent actions to enable self-adaptation. I-centric Services adapt to individual communication spaces and situations. In this context I means I, or individual, Centric means adaptable to I requirements and the individual s environment. The rationales above require intelligence in service provisioning in order to personalize, adapt to situational and environmental conditions, to monitor and to control the individual communication space. An I-centric communications system will provide the intelligence required for modeling the communication space of each individual adapting to its interests, environment, and preferences. The thesis introduces the vision of I-centric communications, followed by the development of a reference model for I-centric communications. Since both, the vision and the reference model, are general, an architectural framework for I-centric communications is introduced later on. This framework is used to design and implement an I-centric communications system. The work in the area of I-centric communications was carried out in cooperation of the Department for Open Communication Systems (OKS) at the Technical University Berlin (TUB) and the Fraunhofer Institute FOKUS. The vision and the reference model, introduced in this thesis, are the results of this cooperation. The main research directions for the cooperation between TUB and FOKUS have been a general model for I-centric Services, the service platform for I-centric Services, and an approach for the interaction of users with I-centric Services. This thesis focuses on I-centric Services and according communication system. The aspects of user interaction are out of scope of this thesis. Nevertheless, these aspects have been analyzed by Stephan Steglich, researcher at the TUB, in a second PhD thesis in parallel. The results of this thesis have been contributed to different national and international projects (BMBF: LiveFutura, VHE, PI-AVIda, IST: WSI, WWRI), standardization bodies (OMG, WWRF), conference papers, and journals by introducing the vision of I-centric communications to a larger auditorium, and by exploiting parts of the developed I-centric systems

Reliable data communication for mobile IP based systems

In der Vergangenheit wurden Endgeräte im wesentlichen mittels drahtgebundener Übertragungstechniken an das Internet angebunden. Derzeit sich im Aufbau befindende bzw. zukünftige drahtlose Mobilkommunikationssysteme bieten auch für mobile Endgeräte einen Internetzugang mit akzeptablen Datenraten. Als Konsequenz wird auch im Bereich der Mobilkommunikation die zuverlässige Datenübertragung im Vergleich zur bereits etablierten - für den Telefondienst eingesetzten - unzuverlässigen Datenübertragung zunehmend an Bedeutung gewinnen. Die zuverlässige Datenübertragung über fehleranfällige, drahtlose Kanäle mittels des im Internet etablierten Transportprotokolls TCP ist Gegenstand der Betrachtungen in dieser Arbeit. Es werden die negativen Auswirkungen der höheren Fehlerwahrscheinlichkeiten auf die einzelnen Protokollmechanismen im Detail diskutiert. Es folgt eine umfassende Analyse in der Literatur vorgeschlagener Verfahren hinsichtlich ihrer Praktikabilität und ihrer Eignung, die Performance Probleme von TCP im drahtlosen Umfeld zu lösen. Der sogenannte 'Indirekte Transportansatz', ein proxybasierter Ansatz, kristallisiert sich bei dieser Analyse als der Ansatz der Wahl heraus. Auf Grund der bei diesem Ansatz in Routern zusätzlich zu verwaltenden verbindungsspezifischen Statusinformation der Transportprotokolle sind - beispielsweise durch die Mobilität der Endgeräte bedingte - Routenänderungen problematisch. Für die hierzu erforderliche sogenannte 'Mobilitätstunterstützung für indirekte Transportansätze' existieren bisher lediglich Verfahren, die aufgrund der sich ergebenden signifikanten Unterbrechungen der Ende-zu-Ende Kommunikation nur schlecht geeignet sind. Die in dieser Arbeit entwickelte, simulativ bewertete und prototypisch implementierte 'Optimierte Mobilitätsunterstützung für indirekte Transportansätze' (OMIT), kann diese Unterbrechungen mittels der Verfahren 'Fast-Forwarding' und 'nebenläufige Migration' vermeiden.In the past, end systems have primarily been connected to the Internet using wired transmission technologies. Presently installed and future wireless mobile communication systems will also provide Internet access and acceptable data rates for mobile end systems. As a consequence, comparing the reliable data service with the available - mainly for the audio service used - unreliable service, the importance of the reliable service will increase within mobile communication systems. The focus of this work is on reliable services and the realization over error prone wireless channels using the transport protocol TCP, that is used within the Internet to implement a reliable end-to-end service. The negative influence of higher error probabilities on TCP's protocol mechanisms is discussed in detail. Furthermore, an extensive analysis of in the literature described proposals to address TCP's performance deficits is included within this work. Practicability and the ability to address TCP's performance deficits are the main criteria of this analysis. The so called 'Indirect Transport Approach', a proxy based approach, turns out to be an appropriate approach. However, the indirect transport approach requires within routers additional - per transport connection - state information. This state information is problematic in the context of routing changes, e.g. caused by the mobility of a mobile end system. Existing proposals for the required so called 'Mobility Support of Indirect Transport Approaches' significantly interrupt the end-to-end communication. Thus, they are unsuitable. These interruptions can be avoided by the so called 'Optimized Mobility Support of Indirect Transport Approaches' (OMIT). Within this work this approach has been developed, investigated via simulations and implemented. The two key mechanisms are: 'Fast-Forwarding' and the 'Concurrent Migration'