This work address the adding, removing and upgrading of network elements in a computer network at run-time. This is already accomplished by Sun Microsystems Jini architecture, but we have investigated if it is possible to create a maintenance system that can handle this, using CORBA. We also want the manual intervention to be minimal. We have discovered that it is possible to create such a system, using CORBA, and that this solution also can handle upgrading a network element at run-time. This report outlines the design of this system, realizing automatic run-time network maintenance.

Knowledge of a network’s entities and the physical connections between them, a network’s physical topology, can be useful in a variety of network scenarios and applications. Administrators can use topology information for fault- finding, inventorying and network planning. Topology information can also be used during protocol and routing algorithm development, for performance prediction and as a basis for accurate network simulations. Specifically, from a network security perspective, threat detection, network monitoring, network access control and forensic investigations can benefit from accurate network topology information. The dynamic nature of large networks has led to the development of various automatic topology discovery techniques, but these techniques have mainly focused on cooperative network environments where network elements can be queried for topology related information. The primary objective of this study is to develop techniques for discovering the physical topology of an Ethernet network without the assistance of the network’s elements. This dissertation describes the experiments performed and the techniques developed in order to identify network nodes and the connections between these nodes. The product of the investigation was the formulation of an algorithm and heuristic that, in combination with measurement techniques, can be used for inferring the physical topology of a target network. / Dissertation (MSc)--University of Pretoria, 2008. / Computer Science / unrestricted

The current Internet architecture presents a barrier to accommodate the vigorous arising demand for deploying new network services and applications. The next-generation architecture views the network virtualization as the gateway to overcome this limitation. Network virtualization promises to run efficiently and securely multiple dedicated virtual networks (VNs) over a shared physical infrastructure. Each VN is tailored to host a unique application based on the user’s preferences. This thesis addresses the problem of the efficient embedding of multiple VNs onto a shared substrate network (SN). The contribution of this thesis are twofold: First, a novel hierarchical SN management framework is proposed that efficiently selects the optimum VN mapping scheme for the requested VN from more than one proposed VN mapping candidates obtained in parallel. In order to accommodate the arbitrary architecture of the VNs, the proposed scheme divides the VN request into smaller subgraphs, and individually maps them on the SN using a variation of the exact subgraph matching techniques. Second, the physical resources pricing policy is introduced that is based on time-ofuse, that reflects the effect of resource congestion introduced by VN users. The preferences of the VN users are first represented through corresponding demand-utility functions that quantify the sensitivity of the applications hosted by the VNs to resource consumption and time-of-use. A novel model of time-varying VNs is presented, where users are allowed to up- or down-scale the requested resources to continuously maximize their utility while minimizing the VNs embedding cost. In contrast to existing solutions, the proposed work does not impose any limitations on the size or topology of the VN requests. Instead, the search is customized according to the VN size and the associated utility. Extensive simulations are then conducted to demonstrate the improvement achieved through the proposed work in terms of network utilization, the ratio of accepted VN requests and the SP profits.

The concept of innovation hubs are increasingly being adopted by different sectors as a means to accelerate innovation. Previous research on innovation hubs have focused on large-scale and trans-regional hubs on its managerial practices instead of its geographical situation. This paper studies an innovation hub in the Northern Swedish city of Skellefteå, in a region historically relying on heavy industry trying to transform into a high technology economy. The study aims to answer the research question: “what are the challenges and opportunities in building and managing an innovation hub to foster innovation in a geographically isolated region with a relatively small population?” To answer this question, interviews with stakeholders in the innovation hub has been conducted as part of a qualitative case study. The results indicate that the region’s large heavy industry companies provide a fertile ecosystem for startups in the digital industry by enabling the necessary supporting industries and infrastructure. Meanwhile, the lack of certain important elements needed in the startup process, most prominently private funding in the form of angel investors and venture capital, pose challenges to the development of the digital startup community in the region.

This thesis focuses on one key theme, which is to understand the construct of organizational networking behaviors in business-to-business markets. It is concerned with two main issues, which are built into the research program of three empirical studies. The first issue is concerned with a systematic understanding of organizational behaviors in response to the embeddedness and interconnectedness of the network of business relationships that every organization has to deal with. Study 1 of the research program explores the concept termed ‘organizational networking behaviors’. This study adopts an industrial network approach, the central tenet of which is that firms undertake a continuous process of interaction with their important partners in the embedding context of the business network. A multi-informant approach, using semi-structured interviews, was used to collect qualitative data from thirty-one executive managers (in fifteen manufacturing firms in the UK). This study identified information acquisition, opportunity enabling, strong-tie resource mobilization and weak-tie resource mobilization as four types of organizational networking behaviors, which are reflected by their respective sub-types. The resulting conceptualization of organizational networking forms the basis for the operationalization of the construct in Study 2. While Study 1 takes an exploratory qualitative approach, Study 2 deploys a confirmatory quantitative approach since it is necessary to confirm/refute the resulting conceptualization and its types from Study 1. A rigorous scale construction and validation process was followed in this study. The conceptualization of the measurement model was carefully considered based on its theoretical underpinning. A second-order formative measurement structure was conceptualized, which required the employment of a multiple indicators and multiple causes (MIMIC) model for the validation of such a measurement model. A dataset of 603 responses was collected and analyzed to confirm the structure of the four types of organizational networking behaviors, which is in line with the results of Study 1.The second issue that the thesis is concerned with is the influences of such organizational networking efforts, which are examined from a firm’s behavioral perspective. Study 3 examines how organizational networking behaviors serve as the driver of a firm’s customer-oriented, competitor-oriented and relationship-oriented behaviors due to the sensing and seizing aspects of networking. It was also hypothesized that a firm’s customer-oriented, competitor-oriented and relationship-oriented behaviors positively affect firm performance. The test of these hypotheses required survey data collection, which was done through an on-line questionnaire. A dataset of 354 responses was collected from UK managers, whose organizations operate in business-to-business markets in either the manufacturing or services sectors. The use of statistical modeling techniques is similar to that of Study 2. The research results indicate that a firm’s network-oriented behaviors positively impact on the development of customer-oriented and competitor-oriented behaviors. They also foster relationship coordination with its important business partners within the network. In addition, the effective management of the firm’s portfolio of relationships is found to mediate the positive impact of network-oriented behaviors on firm profitability.

Transition towards low-carbon energy systems requires an increase in the volume of renewable Distributed Generation (DG), particularly wind and photovoltaic, connected to distribution networks. To facilitate the connection of renewable DG without the need for expensive and time-consuming network reinforcements, distribution networks should move from passive to active methods of operation, whereby technical network constraints are actively managed in real time. This requires the deployment of control solutions that manage network constraints and, crucially, ensure adequate levels of energy curtailment from DG plants by using other controllable elements to solve network issues rather than resorting to generation curtailment only. This thesis proposes a deterministic distribution Network Management System (NMS) to facilitate the connections of renewable DG plants (specifically wind) by actively managing network voltages and congestion in real time through the optimal control of on-load tap changers (OLTCs), DG power factor and, then, generation curtailment as a last resort. The set points for the controllable elements are found using an AC Optimal Power Flow (OPF). The proposed NMS considers the realistic modelling of control by adopting one-minute resolution time-series data. To decrease the volumes of control actions from DG plants and OLTCs, the proposed approach departs from multi-second control cycles to multi-minute control cycles. To achieve this, the decision-making algorithm is further improved into a risk-based one to handle the uncertainties in wind power throughout the multi-minute control cycles. The performance of the deterministic and the risk-based NMS are compared using a 33 kV UK distribution network for different control cycles. The results show that the risk-based approach can effectively manage network constraints better than the deterministic approach, particularly for multi-minute control cycles, reducing also the number of control actions but at the expense of higher levels of curtailment. This thesis also proposes energy storage sizing framework to find the minimum power rating and energy capacity of multiple storage facilities to reduce curtailment from DG plants. A two-stage iterative process is adopted in this framework. The first stage uses a multi-period AC OPF across the studied horizon to obtain initial storage sizes considering hourly wind and load profiles. The second stage adopts a high granularity minute-by-minute control driven by a mono-period bi-level AC OPF to tune the first-stage storage sizes according to the actual curtailment. The application of the proposed planning framework to a 33 kV UK distribution network demonstrates the importance of embedding real-time control aspects into the planning framework so as to accurately size storage facilities. By using reactive power capabilities of storage facilities it is possible to reduce storage sizes. The combined active management of OLTCs and power factor of DG plants resulted in the most significant benefits in terms of the required storage sizes.

Wireless sensor networks are ad hoc networks of tiny battery powered sensor nodes that can organize themselves to form self-organized networks and collect information regarding temperature, light, and pressure in an area. Though the applications of sensor networks are very promising, sensor nodes are limited in their capability due to many factors. The main limitation of these battery powered nodes is energy. Sensor networks are expected to work for long periods of time once deployed and it becomes important to conserve the battery life of the nodes to extend network lifetime. This work examines non-uniform grid-based routing protocol as an effort to minimize energy consumption in the network and extend network lifetime. The entire test area is divided into non-uniformly shaped grids. Fixed source and sink nodes with unlimited energy are placed in the network. Sensor nodes with full battery life are deployed uniformly and randomly in the field. The source node floods the network with only the coordinator node active in each grid and the other nodes sleeping. The sink node traces the same route back to the source node through the same coordinators. This process continues till a coordinator node runs out of energy, when new coordinator nodes are elected to participate in routing. Thus the network stays alive till the link between the source and sink nodes is lost, i.e., the network is partitioned. This work explores the efficiency of the non-uniform grid-based routing protocol for different node densities and the non-uniform grid structure that best extends network lifetime.

The diploma thesis focuses on issue of the corporate network management design that supplies gastronomical customers. Describes possible solution to the problems that are related with the implementation of monitoring system. It contains suggestion of indroducing new work position and documentation (including new guideline), equipment modernization and individual steps to computer network management.

This master's thesis is focuses on problematic of monitoring data in consulting company TG Community Holding a.s. The design will consist of a create monitoring network for a traffic tracking primarily data volume size tracking. It would be a monitoring of atypical events on the network. This master's thesis will be used to implement the proposed solution in the holding.

This paper explores how an all pair shortest path can be obtained in a wireless sensor network when sensors fail. Sensors are randomly deployed in a predefined geographical area, simulating the deployment of sensors from an airplane, and finding shortest path between all the sensors deployed based on distance. A major problem to address in wireless sensor networks is the impact of sensor failures on existing shortest paths in the network. An application is developed to simulate a network and find shortest paths affected by a sensor failure and find alternative shortest path. When a sensor fails, all the shortest paths and all the remaining sensors in the network are checked to see if the sensor failure has any impact on the network. Alternative shortest path is calculated for those paths affected by sensor failures.