38 research outputs found

    AS Domain Tunnelling for User-Selectable Loose Source Routing

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    The use of the Internet as a ubiquitous means of e-commerce, social interaction and entertainment is well established. However, despite service diversity, all traffic is treated the same. Although this clearly “works” and is considered “fair” in terms of net neutrality, there are times when it would be particularly beneficial, if the end-user could have some control over the path his or her traffic takes, either avoiding geographic regions or exploiting lower latency options, should they exist. In this research work, we propose to design and evaluate a scheme that allows end-users to selectively exploit a sequence of tunnels along a path from the source to a chosen destination. The availability of such tunnels is advertised centrally through a broker, with the cooperation of the Autonomous System (AS) domains, allowing end-users to use them if so desired. The closest analogy this scheme is that of a driver choosing to use one or more toll roads along a route to avoid potential congestion or less desirable geographic locations. It thus takes the form of a type of loose source routing. Furthermore, the approach avoids the need for inter-operator cooperation, although such cooperation provides a means of extending tunnels across AS peers. In particular, we aim to ascertain the benefit in terms of delay and reliability for a given degree of tunnel presence within a portion of the Internet. The expectation is that a relatively small number of tunnels may be sufficient to provide worthwhile improvements in performance, at least for some users. Based on this premise, we first design and implement a simulation tool that uses Dijkstra’s Algorithm to calculate the least cost path(s) for differing percentages of randomly placed intra- AS tunnels. We consider end-to-end delay as the cost metric associated with each route and a number of experiments have been performed to confirm the improvement in delays using the tunnels. We then consider the inclusion of a small financial cost that the user would be expected to pay in order to use selected tunnels. Details of the payment mechanism is outside the scope of this thesis, however, the financial burden is taken into account when choosing a route. There is thus a trade-off between delay reduction and a financial penalty. First we explore a heuristic approach using a Genetic Algorithm (GA) we create whereby these conflicting goals are combined into a weighted fitness score associated with the alternative routes, allow a near-optimal compromise to be found, based on the weighting. The downside of this approach is that there is typically a single solution for a given selected weighting. It may be that the user wishes to see the spectrum of alternatives and decide a suitable “sweet spot” based on their current preferences. As such, we then design, implement and evaluate an end-user path selection tool using Multi-Objective Evolutionary Algorithm (MOEA). Unlike the GA, this approach presents a set of optimal solutions for different compromises between the performance objectives, which form a Pareto front. This scheme currently takes into account cost and delay but provides an extensible mechanism for other fitness factors to be considered

    Chapter 11 - Agriculture, forestry and other land use (AFOLU)

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    Agriculture, Forestry, and Other Land Use (AFOLU) plays a central role for food security and sustainable development. Plants take up carbon dioxide (CO2) from the atmosphere and nitrogen (N) from the soil when they grow, re-distributing it among different pools, including above and below-ground living biomass, dead residues, and soil organic matter. The CO2 and other non-CO2 greenhouse gases (GHG), largely methane (CH4) and nitrous oxide (N2O), are in turn released to the atmosphere by plant respiration, by decomposition of dead plant biomass and soil organic matter, and by combustion. Anthropogenic land-use activities (e.g., management of croplands, forests, grasslands, wetlands), and changes in land use / cover (e.g., conversion of forest lands and grasslands to cropland and pasture, afforestation) cause changes superimposed on these natural fluxes. AFOLU activities lead to both sources of CO2 (e.g., deforestation, peatland drainage) and sinks of CO2 (e.g., afforestation, management for soil carbon sequestration), and to non-CO2 emissions primarily from agriculture (e.g., CH4 from livestock and rice cultivation, N2O from manure storage and agricultural soils and biomass burning. The main mitigation options within AFOLU involve one or more of three strategies: reduction / prevention of emissions to the atmosphere by conserving existing carbon pools in soils or vegetation that would otherwise be lost or by reducing emissions of CH4 and N2O; sequestration - enhancing the uptake of carbon in terrestrial reservoirs, and thereby removing CO2 from the atmosphere; and reducing CO2 emissions by substitution of biological products for fossil fuels or energy-intensive products. Demand-side options (e.g., by lifestyle changes, reducing losses and wastes of food, changes in human diet, changes in wood consumption), though known to be difficult to implement, may also play a role. Land is the critical resource for the AFOLU sector and it provides food and fodder to feed the Earth's population of ~7 billion, and fibre and fuel for a variety of purposes. It provides livelihoods for billions of people worldwide. It is finite and provides a multitude of goods and ecosystem services that are fundamental to human well-being. Human economies and quality of life are directly dependent on the services and the resources provided by land. Figure 11.1 shows the many provisioning, regulating, cultural and supporting services provided by land, of which climate regulation is just one. Implementing mitigation options in the AFOLU sector may potentially affect other services provided by land in positive or negative ways. In the Intergovernmental Panel on Climate Change (IPCC) Second Assessment Report (SAR) and in the IPCC Fourth Assessment Report (AR4), agricultural and forestry mitigation were dealt with in separate chapters. In the IPCC Third Assessment Report (TAR), there were no separate sectoral chapters on either agriculture or forestry. In the IPCC Fifth Assessment Report (AR5), for the first time, the vast majority of the terrestrial land surface, comprising agriculture, forestry and other land use (AFOLU), is considered together in a single chapter, though settlements (which are important, with urban areas forecasted to triple in size from 2000 global extent by 2030), are dealt with in Chapter 12. This approach ensures that all land-based mitigation options can be considered together; it minimizes the risk of double counting or inconsistent treatment (e.g., different assumptions about available land) between different land categories, and allows the consideration of systemic feedbacks between mitigation options related to the land surface. Considering AFOLU in a single chapter allows phenomena common across land-use types, such as competition for land and water, co-benefits, adverse side-effects and interactions between mitigation and adaptation to be considered consistently. The complex nature of land presents a unique range of barriers and opportunities, and policies to promote mitigation in the AFOLU sector need to take account of this complexity. In this chapter, we consider the competing uses of land for mitigation and for providing other services. Unlike the chapters on agriculture and forestry in AR4, impacts of sourcing bioenergy from the AFOLU sector are considered explicitly in a dedicated appendix. Also new to this assessment is the explicit consideration of food / dietary demand-side options for GHG mitigation in the AFOLU sector, and some consideration of freshwater fisheries and aquaculture, which may compete with the agriculture and forestry sectors, mainly through their requirements for land and / or water, and indirectly, by providing fish and other products to the same markets as animal husbandry. This chapter deals with AFOLU in an integrated way with respect to the underlying scenario projections of population growth, economic growth, dietary change, land-use change (LUC), and cost of mitigation. We draw evidence from both "bottom-up" studies that estimate mitigation potentials at small scales or for individual options or technologies and then scale up, and multi-sectoral "top-down" studies that consider AFOLU as just one component of a total multi-sector system response. In this chapter, we provide updates on emissions trends and changes in drivers and pressures in the AFOLU sector, describe the practices available in the AFOLU sector, and provide refined estimates of mitigation costs and potentials for the AFOLU sector, by synthesising studies that have become available since AR4. We conclude the chapter by identifying gaps in knowledge and data, providing a selection of Frequently Asked Questions, and presenting an Appendix on bioenergy to update the IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN)

    Agriculture, Forestry and Other Land Use (AFOLU)

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    Agriculture, Forestry, and Other Land Use (AFOLU) is unique among the sectors considered in this volume, since the mitigation potential is derived from both an enhancement of removals of greenhouse gases (GHG), as well as reduction of emissions through management of land and livestock (robust evidence; high agreement). The land provides food that feeds the Earth’s human population of ca. 7 billion, fibre for a variety of purposes, livelihoods for billions of people worldwide, and is a critical resource for sustainable development in many regions. Agriculture is frequently central to the livelihoods of many social groups, especially in developing countries where it often accounts for a significant share of production. In addition to food and fibre, the land provides a multitude of ecosystem services; climate change mitigation is just one of many that are vital to human well-being (robust evidence; high agreement). Mitigation options in the AFOLU sector, therefore, need to be assessed, as far as possible, for their potential impact on all other services provided by land. [Section 11.1
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