On the Benefit of Virtualization: Strategies for Flexible Server Allocation

Virtualization technology facilitates a dynamic, demand-driven allocation and migration of servers. This paper studies how the flexibility offered by network virtualization can be used to improve Quality-of-Service parameters such as latency, while taking into account allocation costs. A generic use case is considered where both the overall demand issued for a certain service (for example, an SAP application in the cloud, or a gaming application) as well as the origins of the requests change over time (e.g., due to time zone effects or due to user mobility), and we present online and optimal offline strategies to compute the number and location of the servers implementing this service. These algorithms also allow us to study the fundamental benefits of dynamic resource allocation compared to static systems. Our simulation results confirm our expectations that the gain of flexible server allocation is particularly high in scenarios with moderate dynamics

Consistent SDNs through Network State Fuzzing

The conventional wisdom is that a software-defined network (SDN) operates under the premise that the logically centralized control plane has an accurate representation of the actual data plane state. Unfortunately, bugs, misconfigurations, faults or attacks can introduce inconsistencies that undermine correct operation. Previous work in this area, however, lacks a holistic methodology to tackle this problem and thus, addresses only certain parts of the problem. Yet, the consistency of the overall system is only as good as its least consistent part. Motivated by an analogy of network consistency checking with program testing, we propose to add active probe-based network state fuzzing to our consistency check repertoire. Hereby, our system, PAZZ, combines production traffic with active probes to periodically test if the actual forwarding path and decision elements (on the data plane) correspond to the expected ones (on the control plane). Our insight is that active traffic covers the inconsistency cases beyond the ones identified by passive traffic. PAZZ prototype was built and evaluated on topologies of varying scale and complexity. Our results show that PAZZ requires minimal network resources to detect persistent data plane faults through fuzzing and localize them quickly while outperforming baseline approaches.Comment: Added three extra relevant references, the arXiv later was accepted in IEEE Transactions of Network and Service Management (TNSM), 2019 with the title "Towards Consistent SDNs: A Case for Network State Fuzzing

Panopticon: Reaping the Benefits of Partial SDN Deployment in Enterprise Networks

The operational challenges posed in enterprise networks, present an appealing opportunity for the software-defined orchestration of the network (SDN). However, the primary challenge to realizing solutions built on SDN in the enterprise is the deployment problem. Unlike in the data-center, network upgrades in the enterprise start with the existing deployment and are budget and resource-constrained. In this work, we investigate the prospect for partial Software Defined Network (SDN) deployment. We present Panopticon, an architecture and methodology for planning and operating networks that combine legacy and upgraded SDN switches. Panopticon exposes an abstraction of a logical SDN in a partially upgraded legacy network, where the SDN benefits extend potentially over the entire network. We evaluate the feasibility of our approach through simulation on real enterprise campus network topologies entailing over 1500 switches and routers. Our results suggest that with only a handful of upgraded switches, it becomes possible to operate most of an enterprise network as a single SDN while meeting key resource constraints

Contactless and spatially structured cooling by directing thermal radiation

In recent years, radiative cooling has become a topic of considerable interest for applications in the context of thermal building management and energy saving. The idea to direct thermal radiation in a controlled way to achieve contactless sample cooling for laboratory applications, however, is scarcely explored. Here, we present an approach to obtain spatially structured radiative cooling. By using an elliptical mirror, we are able to enhance the view factor of radiative heat transfer between a room temperature substrate and a cold temperature landscape by a factor of 92. A temperature pattern and confined thermal gradients with a slope of \~ 0.2~°C/mm are created. The experimental applicability of this spatially structured cooling approach is demonstrated by contactless supercooling of hexadecane in a home-built microfluidic sample. This novel concept for structured cooling yields numerous applications in science and engineering as it provides a means of controlled temperature manipulation with minimal physical disturbance

Modularity and Architecture of PLC-based Software for Automated Production Systems: An analysis in industrial companies

Adaptive and flexible production systems require modular and reusable software especially considering their long term life cycle of up to 50 years. SWMAT4aPS, an approach to measure Software Maturity for automated Production Systems is introduced. The approach identifies weaknesses and strengths of various companie's solutions for modularity of software in the design of automated Production Systems (aPS). At first, a self assessed questionnaire is used to evaluate a large number of companies concerning their software maturity. Secondly, we analyze PLC code, architectural levels, workflows and abilities to configure code automatically out of engineering information in four selected companies. In this paper, the questionnaire results from 16 German world leading companies in machine and plant manufacturing and four case studies validating the results from the detailed analyses are introduced to prove the applicability of the approach and give a survey of the state of the art in industry

Towards Transiently Secure Updates in Asynchronous SDNs

© ACM 2016. This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in Proceedings of the 2016 Conference on ACM SIGCOMM 2016 Conference - SIGCOMM ’16, http://dx.doi.org/10.1145/2934872.2959083.Software-Defined Networks (SDNs) promise to overcome the often complex and error-prone operation of tradi- tional computer networks, by enabling programmabil- ity, automation and verifiability. Yet, SDNs also in- troduce new challenges, for example due to the asyn- chronous communication channel between the logically centralized control platform and the switches in the data plane. In particular, the asynchronous commu- nication of network update commands (e.g., OpenFlow FlowMod messages) may lead to transient inconsisten- cies, such as loops or bypassed waypoints (e.g., fire- walls). One approach to ensure transient consistency even in asynchronous environments is to employ smart scheduling algorithms: algorithms which update subsets of switches in each communication round only, where each subset in itself guarantees consistency. In this demo, we show how to change routing policies in a transiently consistent manner. We demonstrate two al- gorithms, namely, Wayup [5] and Peacock [4], which partition the network updates sent from SDN controller towards OpenFlow software switches into multiple rounds as per respective algorithms. Later, the barrier mes- sages are utilized to ensure reliable network updates.EC/FP7/619609/EU/Unifying Cloud and Carrier Networks/UNIF

A one-pot, water compatible synthesis of pyrimidine nucleobases under plausible prebiotic conditions

Herein, we report a new prebiotically plausible pathway towards a pyrimidine nucleobase in continuous manner. The route involves simultaneous methylation and carbamoylation of cyanoacetylene-derived alpha,beta-unsaturated thioamide with N-methyl-N-nitrosourea (MNU) in aqueous media. This provides S-methylpyrimidinone in one-pot, which can be converted into a variety of 4-substituted pyrimidine nucleobases including cytosine and uracil

Taxonomische und funktionelle Diversität arbuskulärer Mykorrhizasymbiosen im Pflanzenbau

Die arbuskuläre Mykorrhiza (AM) führt zu einer Steigerung der ökologischen Fitness ihrer Pflanzenpartner und kann vielseitig genutzt werden. Sie fungiert dabei im Pflanzennutzungssystem nicht ausschließlich mutualistisch, sondern in einem Kommensalismus-Mutualismus-Kontinuum. Die taxonomische Zusammensetzung der am jeweiligen Standort vorhandenen Mykorrhizapilzgemeinschaften besitzt Einfluss auf die quantitative und qualitative Wirksamkeit der Symbiose, auf die sich weiterhin u. a. die genetische Identität der Wirtspflanze, der Bodennährstoffgehalt, sowie strukturelle Beschaffenheit des Bodens auswirken. Darüber hinaus begründet die genetische Vielfalt unterhalb der Artebene der Mykorrhizapilze die nutzungsrelevante funktionelle Diversität der Symbiosen.Stichwörter: Arbuskuläre Mykorrhizapilze, Intra-spezifische Diversität, Nutzpflanzen, Produktivität, Symbiose, Bodenfaktoren, BodenbearbeitungSummaryNaturally occurring arbuscular mycorrhizal fungi improve ecological fitness of their plant hosts. In agricultural practice, mycorrhizal associations function along a commensalism-mutualism continuum. Species composition of mycorrizal fungal communities in different habitats was found to determine quantitative and qualitative symbiotic performance. Besides this, genotype of the plant host, soil nutrition status, and soil structure were identified to strongly affect symbiotic outcome. Furthermore, mycorrhiza fungi clonal diversity below fungal species level was shown to have considerable influence on functional diversity in terms of a functional complementarity of the fungal inoculum which is important for the agricultural exploitation of the arbuscular mycorrhizal symbiosis.Keywords: arbuscular mycorrhizal fungi, intra-specifc diversity, crops, productivity, symbioses, soil parameters, tillag

Levels of urban green knowledge when planning the multifunctional, inclusive community garden "Ludwigsgarten Braunschweig"

Vor dem Hintergrund der Planung des multifunktionalen, inklusiven Gemeinschaftsgartens „Ludwigsgarten Braunschweig“ wurde herausgearbeitet, welche Inhalte zum Begriff „Stadtgrünwissen“ gezählt werden sollten. Rechtliche und versicherungstechnische Voraussetzungen, städteplanerische Aspekte, botanisches und gartenbauliches Pflanzenwissen, Wissen über die Stadtökologie einschließlich Klima und Biodiversität, gehören zum Stadtgrünwissen ebenso dazu wie die Kenntnisse der Bedürf­nisse und Erwartungen der Nutzer*innen bzw. Bewohner*innen des Quartiers, in dem sich der Garten befindet. Dieses komplexe Stadtgrünwissen war wesentlich für die Vorplanungen des Gartenkonzeptes für den „Ludwigsgarten Braunschweig“, um es über ein agiles Projekt­management unter Partizipation vieler Akteur*innen in die Implementierung überführen zu können. Eine geeignete Kommunikationsstruktur ließ sich über sozialarbeiterische Kompetenz aufbauen. Diese sprach hier die Menschen mit Beeinträchtigung ebenso an, wie die Bewohner*innen des Quartiers aus der Nachbarschaft. Ein Projektmanager erwies sich als die entscheidende Person für die Kommunikation im Projekt und wurde durch eine Expertengruppe mit wechselnder Beset­zung unterstützt. Es wird empfohlen, dem üblichen Planungsvorhaben von Grünflächen eine Teilhabeplanung für alle Akteur*innengruppen voran zu stellen und klare Regeln und Pflichten in einem gemeinsam erarbeiteten Nutzungs- und Managementkonzept folgen zu lassen. Dadurch wird eine aktive und aktivierende Einbindung der Bürger*innen in die städtische Grünplanung, -anlage und -pflege möglich.Against the background of the planning of the multifunctional, inclusive community garden “Ludwigsgarten Braunschweig”, it was worked out which contents should be included in the term “urban green knowledge”. Legal and insurance requirements, urban planning aspects, bota­nical and horticultural knowledge of plants, know­ledge of urban ecology including climate and biodiversity are just as much a part of urban green knowledge as is knowledge of the needs and expectations of the users or residents of the district in which the garden is located. This complex urban green knowledge was essential for the planning of the garden concept for the “Ludwigsgarten Braunschweig” in order to be able to transfer it to the implementation via agile project management with the participation of many actors. A suitable communication structure could be established through social work skills. This addressed the people with disabilities as well as the residents of the neighborhood. A project manager turned out to be the key person for communication in the project and was supported by a group of experts with a rotating cast. It is recommended that the usual planning project for green spaces be preceded by participation planning for all groups of actors and that clear rules and obligations follow in a jointly developed user management concept. This enables citizens to be actively and actively involved in urban green planning, landscaping and maintenance