Virtualization is becoming more and more popular since the hardware that is available today often has theability to run more than just a single machine. The hardware is too powerful in relation to the requirementsof the software that is supposed to run on the hardware, making it inefficient to run too little software ontoo powerful of machines. With virtualization, the ability exists to run a lot of different software on thesame hardware, thereby increasing the efficiency of hardware usage.Virtualization doesn't stop at just virtualizing operating systems or commodity software, but can also beused to virtualize networking components. These networking components include everything from routersto switches and are possible to set up on any kind of virtulized system.When discussing virtualization of networking components, the experssion “Software Defined Networking”is hard to miss. Software Defined Networking is a definition that contains all of these virtualized networkingcomponents and is the expression that should be used when researching further into this subject. There'san increasing interest in these virtualized networking components now in relation to just a few years ago.This is due to company networking becoming much more complex now in relation to the complexity thatcould be found in a network a few years back. More services need to be up inside of the network and a lotof people believe that Software Defined Networking can help in this regard.This thesis aim is to try to find out what kind of differences there are between multiple different softwarerouters. Finding out things like, which one of the routers that offer the highest network speed for the leastamount of hardware cost, are the kind of things that this thesis will be focused on. It will also look at somedifferent aspects of performance that the routers offer in relation to one another in order to try toestablish if there exists any kind of “best” router in multiple different areas.The idea is to build up a virtualized network that somewhat relates to how a normal network looks insmaller companies today. This network will then be used for different types of testing while having thesoftware based router placed in the middle and having it take care of routing between different local virtualnetworks. All of the routers will be placed on the same server and their configuration will be very basicwhile also making sure that each of the routers get access to the same amount of hardware.After initial testing, all routers that perform bad will be opted out for additional testing. This is done tomake sure that there's no unnecessary testing done on routers that seem to not be able to keep up withthe other ones. The results from these tests will be compared to the results of a hardware router with thesame kind of tests used with it in the middle in relation to the tests the software routers had to go through.The results from the testing were fairly surprising, only having one single router being eliminated early onas the remaining ones continued to “battle” one another with more tests. These tests were compared tothe results of a hardware router and the results here were also quite surprising with a much betterperformance in many different areas from the software routers perspective.

The popularity of social networking sites on the World Wide Web has exploded during the past two decades. As more and more K-12 public school teachers choose to actively participate on social networking sites, school leaders and school boards face the increasingly difficult decision about whether or not to enact policies which will enable them to discipline teachers for their online behavior. The purpose of this qualitative case study was to explore the development, interpretation, and significance of one such policy.

Peer-to-peer networks are a common methodology used for content delivery and data sharing on the Internet. The duration of any particular download session is highly dependent on the capacity of the node servers selected as source peers. Recent investigations have shown that specific total download times may deviate significantly from average total download times. This work investigates a novel approach to selecting download server peers that is intended to reduce average total download times and minimize variance of those times from the overall average of download session durations. Typical algorithms used in today's Peer-to-Peer (P2P) systems have improved from simply connecting to a single source peer for the entire download session to an approach where the download content is divided into chunks and a randomly selected source peer is chosen as the source for each chunk. This limits the possibility of an extremely long download session due to the selection of a low capacity download source peer. Prior work has demonstrated that it is better to divide the download session into time slices and download as much as possible from a randomly selected source peer within each time interval rather than staying connected to a poorly performing source peer for the entire time it takes to download a chunk of the source content. This approach minimizes the time spent with a poorly performing source peer and allows the client to move on to a potentially better performing source after a specific, limited interval. Other work has shown that by keeping a history of node performance, it is possible to recognize a poorly performing partner early in a time slice and depart to a new, and hopefully better performing partner, prior to the completion of a time slice (referred to as "choking" a poorly performing peer). These approaches have been shown to reduce average download times and minimize the variance in duration between download sessions. Prior work has also shown that there is value in the use of parallel download streams. As long as the number of streams is kept small (i.e. 4 to 6), minimizing the overhead of maintaining numerous streams and saturation of the available incoming network bandwidth, average download time can be further reduced. The algorithm described in this investigation uses time-based source peer switching and maintains a small number of parallel download streams. At the end of each time interval, it does not randomly replace all source peers but keeps those source peers that are performing relatively better and replaces those performing relatively poorly with randomly selected new source partners. In this way, as the download progresses, parallel downloading typically progresses from a set of better and better performing source partners, therefore reducing average download times and reducing overall variance between download times. This approach has been shown in simulations to reduce average download times by nearly 20% over parallel versions of basic time-based downloads and 8.7% over time-based downloads with the addition of "choking" poorly performing partners. As file sizes increase and/or the heterogeneity of source node service capacities increase, the benefits of this approach to source peer replacement also increases. These improvements are gained while maintaining or further limiting the variance in performance between download sessions. The reduction in average download times and the decrease in variance between download sessions provided by this approach will improve the user experience for users of P2P content distribution systems. This approach should also be applicable to other data distribution systems such as distributed file systems.

The exploding increase of wireless communications combined with the existing inefficient usage of the licensed spectrum gives a strong impetus to the development and standardization of cognitive radio networking and communications. In this dissertation, a framework for Dynamic Spectrum Access (DSA) is first presented, which is the enabling technology for increasing the spectral efficiency of wireless communications. Based on that, Cognitive Radio (CR) can be developed as an enabling technology for supporting the DSA, which means that the wireless users are provided with enhanced capability for sensing the operating radio environment and for exploiting the network side information obtained from this sensing. The DSA concept means that the users of a wireless system are divided into a multi-tiered hierarchy with the primary users (PUs) entitled to protection and with cognitive radio capable secondary users (SUs). The improved spectrum efficiency is obtained by means of a medium access control protocol with knowledge about the statistical properties or available local information of the channels already occupied by PUs as well as knowledge about the interference tolerance within which the interference to PUs is kept to a given level. Related to this, emphasis is laid on the protocol capability to determine the efficiency of the secondary sharing of spectrum. Based on the type of available local information, the capacity of opportunistic communication is investigated for three models. These are: with dynamic, distributed channels information; with dynamic, parallel channels information; and under a dynamic sub-channels allocation scheme. The results indicate that this capacity is robust with reference to the uncertainty associated with localized sensing of distributed dynamic channels and with timely sensing of parallel dynamic channels. The extension to dynamic parallel sub-channels enables resource allocation to be carried out in sub-channels. The analytical results on the performance of sub-channel allocation indicate a robust traffic capacity in terms of blocking probability, drop-out probability and delay performance as function of PUs traffic loads.

Purpose: The purpose of this study is to examine the factors that influence the underrepresentation of women in managerial positions in engineering sector. The study is based on the fact that there are less female leaders both in management and in engineering. Design/Methodology/Approach: The method used in order to accomplish this research is a qualitative approach. The primary data was collecting by semi-structured interviews with employees of the case company (ABB). The sample consists of ten employees, males and females, who hold different positions in the company. Findings: The empirical findings and the analysis show the factors regarding the underrepresentation of women in managerial positions. The study indicates that glass ceiling, gender stereotyping, engineering culture and balancing professional and family life, are major obstacles in women‘s career today. Limitations: I limited my study to only one engineering company therefore the results cannot be generalized for the whole engineering industry. Also, even though this study examines why women are underrepresented in engineering industry, I interviewed both male and female employees in order to illustrate both perspectives about the issue. Contribution: This study confirms the existing theories regarding the affect of underrepresentation of women in engineering industry and highlights the facts that delay women‘s advancement. Engineering culture does not encourage mentoring towards women and women are seen as outsiders in networking activities. Thus, this study gives the opportunity to managers in engineering to consider the reality about females in the sector in order to improve the current situation.

Magister Artium (Development Studies) - MA(DVS) / The main aim of this study was to make contributions to the body of literature on social enterprises, and more specifically in an African context. The nascent nature of social enterprises as an organisational structure is one of the reasons that the body of research and literature is not as expansive as other more established research fields. Social enterprises differ from traditional commercial enterprises in that they bridge the gap between commercial growth, and social and economic development goals. For the purpose of this study, social enterprises refer to any business that pursues commercial activity to address a social problem. They are becoming more noticeable as a driver of sustainable job creation, service delivery, social development and economic growth. Ensuring their sustainability is expected to have positive economic consequences, which is why studying social enterprise sustainability is important and even more so for developing countries. Qualitative methodology was used to collect data. Purposive sampling was employed to select the sample that was included in the case study in Cape Town. In-depth, semi-structured interviews were conducted to gather information. The data was analysed using content thematic analysis to explore and interpret the meaning of the participants’ views and experiences. A networking approach of the social capital theory was used as the theoretical framework that provided a guide on the discussion of the findings. For the purpose of this study, social capital was defined as the resources embedded in networks. The findings indicated that the social entrepreneurs’ did not consider networking as the sole contributing factor to social enterprise sustainability, but rather the contribution of multidimensional factors. The resources embedded in networks that were considered valuable were: 1. Information and innovation, 2. Credibility, 3. Mentorship and advice, and 4. Support. The participants also gave their opinions on policies that would create favourable conditions for sustainable social enterprises i.e. information accessibility, public-private partnerships, and education and training. This study makes contributions to literature in an African context and to social enterprise practice.

Magister Artium (Sport, Recreation and Exercise Science) - MA(SRES) / Social networking sites are important communication tools used in different industries including the sports industry. Professional athletes, coaches, spectators, journalists, and broadcasters from nearly every sports code maintain a social media presence. The rapid growth in the use of social networks in sport and the challenging economic climate launched an urgent need for sport administration departments at universities to understand SNSs and how student spectators use these sites in the realm of university sport. This understanding serves as an attempt to enhance spectator attendance at university sports games through the use of SNSs by integrating these sites into marketing strategies. Sports spectators are key constituents of sports event attendance, however, little is known regarding whether a relationship exists between students’ activities on SNSs and their spectator behaviour. Subsequently, the purpose of this study was to examine and describe the relationship between the use of SNSs and student spectator behaviour in university sport by considering attendance, loyalty, trust, and commitment as determinants of behaviour. A quantitative methodological approach was adopted to collect data, using a cross-sectional research design. By applying a random sampling method, 540 full-time registered university students provided consent to participate in this study. An online survey was distributed to the entire student population, N=24000. All significance levels were set at p<0.05. Data were analyzed using the Statistical Package for Social Science (SPSS) V.25 software. Results showed statistical significance, p<0.00, for the relationship between the use of SNSs and student spectator behaviour during student spectator attendance of university sports games. No statistical significance was found in the relationship between the use of SNSs and student spectator behaviour before and after student spectator attendance of university sports games. These results suggest that greater investment should be placed in marketing through SNSs in order to develop, increase, and retain longstanding relationships of loyalty, trust, and commitment with student spectators in the fast-growing segment of social media and spectatorship.

ABSTRACT WOULD NOT LOAD ON DSpace.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / Data-intensive research computing requires the capability to transfer les over long distances at high throughput. Stateful rewalls introduce su cient packet loss to prevent researchers from fully exploiting high bandwidth-delay network links [25]. To work around this challenge, the science DMZ design [19] trades o stateful packet ltering capability for loss-free forwarding via an ordinary Ethernet switch. We propose a novel extension to the science DMZ design, which uses an SDN-based rewall. This report introduces NFShunt, a rewall based on Linux's Net lter combined with OpenFlow switching. Implemented as an OpenFlow 1.0 controller coupled to Net lter's connection tracking, NFShunt allows the bypass-switching policy to be expressed as part of an iptables rewall rule-set. Our implementation is described in detail, and latency of the control-plane mechanism is reported. TCP throughput and packet loss is shown at various round-trip latencies, with comparisons to pure switching, as well as to a high-end Cisco rewall. Cost, as well as operations and maintenance aspects, are compared and analysed. The results support reported observations regarding rewall introduced packet-loss, and indicate that the SDN design of NFShunt is a technically viable and cost-e ective approach to enhancing a traditional rewall to meet the performance needs of data-intensive researchers / GS2016

A research report submitted to the Faculty of Engineering and the Built Environment of the University of the Witwatersrand in partial fulfilment of the requirements for the degree of Master of Science in Engineering February 2017 / Software-defined networking (SDN) is the physical separation of the control and data planes in networking devices. A logically centralised controller plane which uses a network-wide view data structure to control several data plane devices is another defining attribute of SDN. The centralised controllers and the network-wide view data structure are difficult to scale as the network and the data it carries grow. Solutions which have been proposed to combat this challenge in SDN lack the use of the statistical properties of the workload or network traffic seen by SDN controllers. Hence, the objective of this research is twofold: Firstly, the statistical properties of the controller workload are investigated. Secondly, Autoregressive Integrated Moving Average Models (ARIMA) and Artificial Neural Network (ANN) models are investigated to establish the feasibility of forecasting the controller workload signal. Representations of the state of the controller plane in the network-wide view in the form of forecasts of the controller workload will enable control applications to detect dwindling controller resources and therefore alleviate controller congestion. On the other hand, realistic statistical traffic models of the controller workload variable are sought for the design and evaluation of SDN controllers. A data center network prototype is created by making use of an SDN network emulator called Mininet and an SDN controller called Onos. It was found that 1–2% of flows arrive within 10 s of each other and more than 80% have inter-arrival times in the range of 10 s–10ms. These inter-arrival times were found to follow a beta distribution, which is similar to findings made in Machine Type Communications (MTC). The use of ARIMA and ANN to forecast the controller workload established that it is feasible to forecast the workload seen by SDN controllers. The accuracy of these models was found to be comparable for continuously valued time series signals. The ANN model was found to be applicable even in discretely valued time series data. / MT2017