A Flexible Traffic Shaper for High Speed Networks: Design and Comparative Study with Leaky Bucket

Maximizing bandwidth utilization and providing performance guarantees, in the context of multimedia networking, are two incompatible goals. Heterogeneity of the multimedia sources calls for effective traffic control schemes to satisfy their diverse Quality of Service (QoS) requiremnets. These include admission control at connection set up, traffic control at the source ends and efficient scheduling schemes at the switches. The emphasis in this paper is on traffic control at the source end. Most multimedia sources are bursty in nature. Traffic shapers have been mainly studied hitherto from the point of view of their effectiveness in smoothing the burstiness. Leaky Bucket (LB) scheme, to cite an example, is a mean rate policer smoothing at the token generation rate. Studies on bursty sources show that burstiness promotes statistical multiplexing at the cost of possible congestion. Smoothing, on the other hand, helps in providing guarantees at the cost of utilization. Thus need for a flexible scheme which can provide a reasonable compromise between utilization and performance is imminent. Recent studies [10, 12] have also questioned the suitability of LB for policing real-time traffic due to the excessive delays. We argue for a policy which is less stringenton short term burstiness than the LB. We propose a new traffic shaper which can adjust the burstiness of the input traffic to obtain reasonable bandwidth utilization while maintaining statistical service guarantees. The performance study is conducted in two parts. In the first part, we study the effect of varying the shaper parameters on the input characteristics. In the second part, we dimension our scheme and a LB equivalently and compare the mean and peak rate policing behavior with delay and loss as the performance parameters. Adopting a less stringent attitude towards short term burstiness is shown to result in considerable advantage while policing real-time traffic. Future research possibilities in this topic are explored. (Also cross-referenced as UMIACS-TR-95-71

Design & Performance Study of a Flexible Traffic Shaper for High Speed Networks

In networks supporting distributed multimedia, maximizing bandwidth utilization and providing performance guarantees are two incompatible goals. Heterogeneity of the multimedia sources calls for effective congestion control schemes to satisfy the diverse Quality of Service (QoS) requirements of each application. These include admission control at connection set up, traffic control at the source ends and efficient scheduling schemes at the switches. The emphasis in this paper is on traffic control at the source ends. Traffic control schemes have two functional roles. One is traffic enforcement as a supplement to the admission control policy. The other is shaping the input traffic so that it becomes amenable to the scheduling mechanism at the switches for providing the required QoS guarantees. Studies on bursty sources have shown that burstiness promotes statistical multiplexing at the cost of possible congestion. Smoothing the traffic helps in providing guarantees at the cost o f bandwidth utilization. The need for a flexible scheme which can provide a reasonable compromise between the utilization and guarantees is imminent. We present the design and performance study of a flexible traffic shaper which can adjust the burstiness of input traffic to obtain reasonable utilization while maintaining statistical service guarantees. The performance of the traffic shaper for bursty sources is studied using simulation. (Also cross-referenced as UMIACS-TR-95-72

A Generic Architecture for Programmable Traffic Shaper for High Speed Networks

Traffic shapers by preventing congestion and smoothing the traffic, play an important role in realizing the traffic control schemes employed in high speed networks to ensure the Quality of Service (QoS) requirements of the application. In this report, we present a generic architecture for programmable traffic shaper for high speed networks. The programmability of the proposed architecture is illustrated by implementing some of the existing traffic shaping schemes. The architectural design issues of the proposed scheme are described and discussed. (Also cross-referenced as UMIACS-TR-95-75

Plan or React? Analysis of Adaptation Costs and Benefits Using Integrated Assessment Models

This report examines adaptation and mitigation within an integrated framework. Global and regional costs of adaptation are assessed dynamically and the resulting benefits are quantified. This is accomplished by developing a framework to incorporate adaptation as a policy variable within three Integrated Assessment Models (IAMs); the global Dynamic Integrated model of Climate and the Economy (DICE), the Regional Integrated model of Climate and the Economy (RICE), and the World Induced Technical Change Hybrid (WITCH) model. The framework developed here takes into account investments in reactive adaptation and in adaptation “stocks”, as well as investments in building adaptive capacity. This report presents the first inter-model comparison of results on adaptation costs using the emerging category of adaptation-IAMs. Results show that least-cost policy response to climate change will need to involve subsantial amounts of mitigation efforts, investments in adaptation stock, reactive adaptation measures and adaptive capacity to limit the remaining damages

State of the Art on Neural Rendering

Efficient rendering of photo-realistic virtual worlds is a long standing effort of computer graphics. Modern graphics techniques have succeeded in synthesizing photo-realistic images from hand-crafted scene representations. However, the automatic generation of shape, materials, lighting, and other aspects of scenes remains a challenging problem that, if solved, would make photo-realistic computer graphics more widely accessible. Concurrently, progress in computer vision and machine learning have given rise to a new approach to image synthesis and editing, namely deep generative models. Neural rendering is a new and rapidly emerging field that combines generative machine learning techniques with physical knowledge from computer graphics, e.g., by the integration of differentiable rendering into network training. With a plethora of applications in computer graphics and vision, neural rendering is poised to become a new area in the graphics community, yet no survey of this emerging field exists. This state-of-the-art report summarizes the recent trends and applications of neural rendering. We focus on approaches that combine classic computer graphics techniques with deep generative models to obtain controllable and photo-realistic outputs. Starting with an overview of the underlying computer graphics and machine learning concepts, we discuss critical aspects of neural rendering approaches. This state-of-the-art report is focused on the many important use cases for the described algorithms such as novel view synthesis, semantic photo manipulation, facial and body reenactment, relighting, free-viewpoint video, and the creation of photo-realistic avatars for virtual and augmented reality telepresence. Finally, we conclude with a discussion of the social implications of such technology and investigate open research problems

Forty Years of Climate and Land-Cover Change and its Effects on Tourism Resources in Kilimanjaro National Park

This study explores the effects of observed changes in rainfall, temperature and land cover on the physical and sightseeing aspects of trekking in Kilimanjaro National Park. The impact analysis is organised around hazard-activity pairs approach, combinations of environmental change aspects (such as higher temperatures) and tourism activities (such as trekking and sightseeing). The results suggest that higher temperatures and reduced rainfall have lowered the risks of landslides, rock fall and mountain sickness, improving physical trekking conditions. Changes in land cover have affected sightseeing: there now are more flowers and groundsels to admire and less wildlife, waterfalls and snow. In the short term, the disappearing snow may give rise to “last chance tourism”, increasing visitation, but eventually, the loss of snow and forest cover will likely decrease the number of tourists. The paper concludes that effective management of the attractions in the expanding heathlands is the most promising option to limit the losses.</p

Playing the role of a ‘boundary organisation’: getting smarter with networking

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Summary for policymakers

The Working Group III contribution to the IPCC Fifth Assessment Report (WGIII AR5) provides a comprehensive assessment of all relevant options for mitigating climate change through limiting or preventing greenhouse gas emissions, as well as activities that remove them from the atmosphere. It draws on scientific literature accepted for publication prior to 4 October 2013. The WGIII Summary for Policymakers was approved at the Twelfth Session of Working Group III, held in Berlin, Germany, from 7 to 11 April, 2014. During the session, the IPCC plenary also accepted the underlying scientific and technical assessment, which stands at 2000 pages, including more than 700 pages of references

Technical summary

The Working Group III (WGIII) contribution to the IPCC's Fifth Assessment Report (AR5) assesses literature on the scientific, technological, environmental, economic and social aspects of mitigation of climate change. It builds upon the WGIII contribution to the IPCC's Fourth Assessment Report (AR4), the Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) and previous reports and incorporates subsequent new findings and research. Throughout, the focus is on the implications of its findings for policy, without being prescriptive about the particular policies that governments and other important participants in the policy process should adopt. In light of the IPCC's mandate, authors in WGIII were guided by several principles when assembling this assessment: (1) to be explicit about mitigation options, (2) to be explicit about their costs and about their risks and opportunities vis-a-vis other development priorities, (3) and to be explicit about the underlying criteria, concepts, and methods for evaluating alternative policies. This summary offers the main findings of the report

Prospect theory, mitigation and adaptation to climate change

Climate change is one of the most pressing challenges in current environmental policy. Appropriate policies intended to stimulate efficient adaptation and mitigation should not exclusively rely on the assumption of the homo oeconomicus, but take advantage of well-researched alternative behavioural patterns. Prospect theory provides a number of climate-relevant insights, such as the notion that evaluations of outcomes are reference dependent, and the relevance of perceived certainty of outcomes. This paper systematically reviews what prospect theory can offer to analyse mitigation and adaptation. It is shown that accounting for reference dependence and certainty effects contributes to a better understanding of some well-known puzzles in the climate debate, including (but not limited to) the different uptake of mitigation and adaptation amongst individuals and nations, the role of technical vs. financial adaptation, and the apparent preference for hard protection measures in coastal adaptation. Finally, concrete possibilities for empirical research on these effects are proposed