Scalability and Resilience Analysis of Software-Defined Networking

Software-defined Networking (SDN) ist eine moderne Architektur für Kommunikationsnetze, welche entwickelt wurde, um die Einführung von neuen Diensten und Funktionen in Netzwerke zu erleichtern. Durch eine Trennung der Weiterleitungs- und Kontrollfunktionen sind nur wenige Kontrollelemente mit Software-Updates zu versehen, um Veränderungen am Netz vornehmen zu können. Allerdings wirft die Netzstrukturierung von SDN neue Fragen bezüglich Skalierbarkeit und Ausfallsicherheit auf, welche in dezentralen Netzstrukturen nicht auftreten. In dieser Arbeit befassen wir uns mit Fragestellungen zu Skalierbarkeit und Ausfallsicherheit in Bezug auf Unicast- und Multicast-Verkehr in SDN-basierten Netzen. Wir führen eine Komprimierungstechnik für Routingtabellen ein, welche die Skalierungsproblematik aktueller SDN Weiterleitungsgeräte verbessern soll und ermitteln ihre Effizienz in einer Leistungsbewertung. Außerdem diskutieren wir unterschiedliche Methoden, um die Ausfallsicherheit in SDN zu verbessern. Wir analysieren sie auf öffentlich zugänglichen Netzwerken und benennen Vor- und Nachteile der Ansätze. Abschließend schlagen wir eine skalierbare und ausfallsichere Architektur für Multicast-basiertes SDN vor. Wir untersuchen ihre Effizienz in einer Leistungsbewertung und zeigen ihre Umsetzbarkeit mithilfe eines Prototypen.Software-Defined Networking (SDN) is a novel architecture for communication networks that has been developed to ease the introduction of new network services and functions. It leverages the separation of the data plane and the control plane to allow network services to be deployed solely in software. Although SDN provides great flexibility, the applicability of SDN in communication networks raises several questions with regard to scalability and resilience against network failures. These concerns are not prevalent in current decentralized network architectures. In this thesis, we address scalability and resilience issues with regard to unicast and multicast traffic for SDN-based networks. We propose a new compression method for inter-domain routing tables to address hardware limitations of current SDN switches and analyze its effectiveness. We propose various resilience methods for SDN and identify their key performance indicators in the context of carrier-grade and datacenter networks. We discuss the advantages and disadvantages of these proposals and their appropriate use cases. Finally, we propose a scalable and resilient software-defined multicast architecture. We study the effectiveness of our approach and show its feasibility using a prototype implementation

Resilient and Scalable Forwarding for Software-Defined Networks with P4-Programmable Switches

Traditional networking devices support only fixed features and limited configurability. Network softwarization leverages programmable software and hardware platforms to remove those limitations. In this context the concept of programmable data planes allows directly to program the packet processing pipeline of networking devices and create custom control plane algorithms. This flexibility enables the design of novel networking mechanisms where the status quo struggles to meet high demands of next-generation networks like 5G, Internet of Things, cloud computing, and industry 4.0. P4 is the most popular technology to implement programmable data planes. However, programmable data planes, and in particular, the P4 technology, emerged only recently. Thus, P4 support for some well-established networking concepts is still lacking and several issues remain unsolved due to the different characteristics of programmable data planes in comparison to traditional networking. The research of this thesis focuses on two open issues of programmable data planes. First, it develops resilient and efficient forwarding mechanisms for the P4 data plane as there are no satisfying state of the art best practices yet. Second, it enables BIER in high-performance P4 data planes. BIER is a novel, scalable, and efficient transport mechanism for IP multicast traffic which has only very limited support of high-performance forwarding platforms yet. The main results of this thesis are published as 8 peer-reviewed and one post-publication peer-reviewed publication. The results cover the development of suitable resilience mechanisms for P4 data planes, the development and implementation of resilient BIER forwarding in P4, and the extensive evaluations of all developed and implemented mechanisms. Furthermore, the results contain a comprehensive P4 literature study. Two more peer-reviewed papers contain additional content that is not directly related to the main results. They implement congestion avoidance mechanisms in P4 and develop a scheduling concept to find cost-optimized load schedules based on day-ahead forecasts

Kommunikation und Bildverarbeitung in der Automation

In diesem Open-Access-Tagungsband sind die besten Beiträge des 9. Jahreskolloquiums "Kommunikation in der Automation" (KommA 2018) und des 6. Jahreskolloquiums "Bildverarbeitung in der Automation" (BVAu 2018) enthalten. Die Kolloquien fanden am 20. und 21. November 2018 in der SmartFactoryOWL, einer gemeinsamen Einrichtung des Fraunhofer IOSB-INA und der Technischen Hochschule Ostwestfalen-Lippe statt. Die vorgestellten neuesten Forschungsergebnisse auf den Gebieten der industriellen Kommunikationstechnik und Bildverarbeitung erweitern den aktuellen Stand der Forschung und Technik. Die in den Beiträgen enthaltenen anschaulichen Beispiele aus dem Bereich der Automation setzen die Ergebnisse in den direkten Anwendungsbezug

Envisioned Environments and the Social Imaginary in Medieval English Literature: Interactions of Mind, Culture, and Narrative, 700–1400 AD

This diachronic analysis of narrative in Old and Middle English texts from the eighth to fifteenth centuries builds upon recent cognitive explorations in both medieval literature and narratology to identify and contrast certain enduring themes in OE and ME visionary texts. In attending to the evolution of conceptions of the self, and each conception’s embeddedness in the social imaginary of a place and time, multi-layered new readings emerge of the Old English poems The Dream of the Rood, and Guðlac A and Guðlac B (in addition to the prose Life of St Guðlac); and the Middle English poems St Erkenwald; Pearl; and Piers Plowman. While previous studies have noted the importance of society to the role of the fourteenth-century ‘public poet’, this analysis proposes a much earlier, enduring link between medieval narratives of dream, visions, and marvels; the thinking, speaking self; and the larger social imaginary. The application of extended cognition to envisioned people, objects, and environments in poetic English narrative moves critical discussion beyond the formation of the dream-vision genre, toward an awareness that medieval authors could treat any environment as more or less imagined and sense-bearing. As the worked examples demonstrate, destabilisation of social structures is reflected in the disorganisation of these envisioned environments. Individual focalisation both ‘personalises’ these stresses and attempts to articulate a new, stable environment through reorganisation of elements of the social imaginary

Swarm-Based Drone-as-a-Service for Delivery

There has been a growing interest in the applications of drones as a cost-effective, efficient, and environmentally friendly alternative in various domains. Particularly in the context of delivery services, the demand for contactless and efficient delivery solutions has surged. Drone delivery offers faster and greener deliveries. However, existing methods focus primarily on point-to-point delivery, limiting their potential for optimisation. This thesis proposes a novel approach to servitise drone delivery by operating through a skyway network composed of building rooftops, enabling drones to traverse between source and destination while recharging at intermediate nodes. Although single drone delivery offers numerous advantages, it faces significant challenges in scenarios where multiple packages require simultaneous delivery. Flight regulations, which often limit the carrying capacity of individual drones, necessitate the exploration of alternative solutions. Therefore, this thesis presents a novel Swarm-Based Drone-as-a-Service (SDaaS) model and framework for multiple package delivery. The proposed framework prioritises the composition of services that optimise Quality of Service (QoS) factors, such as delivery time and energy consumption. This thesis identifies swarm-specific constraints and leverages the unique characteristics of drone swarms. It explores swarm formations, in-flight wireless charging between drones, and allocation problems to maximise drone utilisation for consumer deliveries. Furthermore, this research investigates the recommendation of services to consumers based on their preferences, aiming to increase their satisfaction. Moreover, the framework addresses the resilience of SDaaS by addressing issues related to drone soft failures and their impact on other swarm members. Ultimately, this work paves the way for the widespread adoption and optimisation of swarm-based drone services in the context of last-mile delivery

The end of stigma? Understanding the dynamics of legitimisation in the context of TV series consumption

This research contributes to prior work on stigmatisation by looking at stigmatisation and legitimisation as social processes in the context of TV series consumption. Using in-depth interviews, we show that the dynamics of legitimisation are complex and accompanied by the reproduction of existing stigmas and creation of new stigmas

Automated Improvement of Software Architecture Models for Performance and Other Quality Attributes

Quality attributes, such as performance or reliability, are crucial for the success of a software system and largely influenced by the software architecture. Their quantitative prediction supports systematic, goal-oriented software design and forms a base of an engineering approach to software design. This thesis proposes a method and tool to automatically improve component-based software architecture (CBA) models based on such quantitative quality prediction techniques