· · · Institutional Repository

This thesis describes the development of a simulation and capacity management tool for generic networks. As a case study KPN's Ethernet network is analysed. The tool can be used to calculate various network metrics that are used in complex network studies. It can also be used to display a geographically correct view of the network, as well as a graph view. Extensive filtering functions allow the user to analyse different parts or layers of the network. Multiple vpns can be defined over the network and traffic can be simulated for these vpns. At each node and every link the simulated traffic can be monitored and logged. This is done for different scenarios in the case study network. Finally a way to optimise the logical topology at different traqffic loads is investigated.

Optical networks employing the wavelength division multiplexing (WDM) technology are promising solutions to the ever increasing demand for bandwidth. The use of WDM allows aggregation of many channels onto a single fibre without the need of high speed optoelectronic devices for end users. In WDM networks, as the optical signals traverse multiple links their quality deteriorates due to the physical impairments they encounter. This necessitates regeneration of the signals at the intermediate nodes so that the signals will reach the destination with an acceptable level of quality. In addition, due to the frequent occurrence of fiber cuts and the tremendous amount of data transported, survivability, which is the ability to reconfigure and reestablish communication upon failure, is indispensable in WDM networks. Survivability is of critical importance in high-speed optical communication networks. These days, network survivability along with impairment-aware routing is of great interest to telecommunication system vendors, service providers and end users. This thesis work focuses on solving impairment-aware survivable routing in WDM networks. We have proposed and implemented exact and heuristic algorithms that solve survivable regenerator placement and survivable impairment-aware routing problems in WDM networks.

This thesis has two main topics. On the one hand it discusses how the robustness of a network can be increased as efficient as possible, where connectivity is treated as a robustness measure. On the other hand It treats capacity management of a network when it is still in its design phase. In particular, it shows how bandwidth management can be done on the network edges, while it also gives an implication to prioritize the vertices based on their relative importance. One of KPN's mobile core networks is treated as a case study.

This thesis describes the implementation of available bandwidth link-state update policies for Quality of Service routing. Periodic, threshold-based and class-based policies are described and implemented in a QoS router testbed, using Quagga and its OSPF-API for low-level communications. The implementation is thoroughly tested using unit tests and simulated traffic. A performance comparison of the link-state update policies is done, using two different scenarios. The results of this comparison show that determining the right parameters for the policy is more important than the kind of policy used. The performance of the policies is generally worse than in previous work, due to the absence of explicit flow admission control, which makes it impossible to account for traffic until after it has been sent. The results also indicate that the use of a moving average instead of a hold-down timer leads to less link-state updates, while not impacting performance.

Mass processing of social media posts has been brought to scientists' attention during the last decade. The massive growth of online social networks, like Twitter and Facebook, have created a need for determining peoples' opinions and moods through these means. This thesis constitutes a research on measuring users' sentiment upon a particular subject by analysing their posts. Establishing an efficient sentiment measurement technique, can be used into estimating popularity of products or persons. For separating subjective from objective posts, a hybrid classifier based on the syntax analysis of texts, is proposed, performing clearly better than existing classifying tools. Moreover, a new sentiment evaluation technique for measuring the polarity and magnitude of posts' sentiment is described and tested over different social media. Results are compared to various real ratings and show that this approach can have a promising accuracy on sentiment establishment of online posts.

This thesis presents a control architecture and utility maximization mechanisms for a smart grid based energy community. The particular focus is upon a central server based, utility-oriented energy community which is composed of producer-consumer (prosumer) households each having a home gateway, an energy management system, smart meters, production units and appliances. To find out how such an energy community could be optimally managed from a central server, the type of intelligence required for the different nodes in the energy network has been identified. In addition, different control mechanisms that enable the energy community to make an optimal use of its energy resources are explored. Moreover, utility maximization mechanisms have been implemented on the aggregate energy profile of the energy community targeting three main objectives namely maximizing the aggregate greenness, minimizing the aggregate energy cost and maximizing the prosumers’ comfort. Maximizing the aggregate greenness aims to maximize the level of consumption of renewable energy resources using a novel mechanism that reduces the difference between the supply of and demand for renewable energy resources. Minimizing the aggregate energy cost aims to reduce the peak to average ratio of the aggregate energy profile of the energy community using direct mechanisms for energy cost minimization and a novel appliance based pricing scheme. Maximizing the prosumers’ comfort aims to preserve the schedule preference of prosumers. The mechanisms above are designed and implemented under a research setting of a renewable energy company that manages an energy community composed of central servers which control household, building and/or industrial prosumers.

The present Low Voltage (LV) grid, which until recently was mainly composed of passive electrical components (consumers), is being gradually overrun by active electrical components (prosumers), who not only consume but also generate and share power locally. This development is introducing changes in the operational dynamics of the LV grid that could result in voltage stability problems and the violation of infrastructural constraints if not well managed. A re-design of the present LV grid is, therefore, imperative to enable it meet these new requirements. This thesis was aimed at studying the influence of topological metrics on the operational performance of the LV grid in view of current developments in energy consumer behaviour with a view to proposing the topological changes and/or modifications in network architecture that would yield optimal outcomes. We modelled the present LV grid as a radial network, and compared it to three other network models -random, small-world and scale-free networks- under different loading scenarios. We proposed novel structural and operational metrics that are suitable for the LV grid, and analysed the networks in terms of these metrics. We also compared their robustness under different attack scenarios and demonstrated the correlation between the structural and the operational metrics, thus, identifying important structural metrics that need to be optimized to improve the future LV grid performance. Finally, we then investigated the possible modifications of the radial network model of the present LV grid that would yield similar results. The results highlighted the structural weaknesses of the present LV grid under futuristic and simultaneous loading conditions and presented the scale-free model as the most suitable architecture for the future LV grid as it out-performed all the other network models under similar loading conditions. They also showed that the insertion of additional links at critical positions in the radial network could achieve similar results. We therefore proposed this structural modification as a more cost-effective approach to improved operational performance of the LV grid.

The host-to-host IP model currently supporting the Internet does not suffice in supporting current-day content distribution in the form of content-sharing via peer-to-peer applications, real-time media streaming and social networks. Since the design of IP, the usage of the Internet has changed from a messaging and few-to-few information sharing system to a fewto-many content distribution system where many users request large amounts of overlapping information. Running a content distribution network over a host-to-host network appears to be very inefficient since every piece of content needs to travel the complete distribution-chain from generator to consumer every time it is requested. The result is that identical pieces of information will often redundantly travel the same links and routers. Information Centric Networking tries to solve this problem by proposing route-by-name instead of route-by-address mechanisms. This enables networks to be optimized for contentdistribution instead of connections and allows routers to cache often requested pieces of content in memory. In this thesis we will attempt to solve problems that arise at the introduction of a new globally routeable network, enabling clients and networks to be a full member (both consumer and generator) on a global Information Centric Network. The topics discussed vary from dynamic end-user configuration and generating globally unique names in order to share information on the Information Centric Network, via mapping techniques to decrease routing complexity, to proposing a transition mechanism that dynamically creates IP encapsulating tunnels between disconnected Information Centric Networks. In short, we discuss a multitude of problems which need to be addressed in order to assist the global implementation of an Information Centric Network.