This thesis presents a scalable service-oriented architecture for the demand-driven deployment of location-neutral software services, using an end-to-end or ‘holistic’ approach to address identified shortcomings of the traditional Web Services model. The architecture presents a multi-endpoint Web Service environment which abstracts over Web Service location and technology and enables the dynamic provision of highly-available Web Services. The model describes mechanisms which provide a framework within which Web Services can be reliably addressed, bound to, and utilized, at any time and from any location. The presented model eases the task of providing a Web Service by consuming deployment and management tasks. It eases the development of consumer agent applications by letting developers program against what a service does, not where it is or whether it is currently deployed. It extends the platform-independent ethos of Web Services by providing deployment mechanisms which can be used independent of implementation and deployment technologies. Crucially, it maintains the Web Service goal of universal interoperability, preserving each actor’s view upon the system so that existing Service Consumers and Service Providers can participate without any modifications to provider agent or consumer agent application code. Lastly, the model aims to enable the efficient consumption of hosting resources by providing mechanisms to dynamically apply and reclaim resources based upon measured consumer demand.

[pt] Principalmente nos últimos anos, diversos pesquisadores tem ressaltado a importância da obtenção de um método para seleção de tamanho de janelas de uma rede de computadores. A dissertação em pauta se propõe a apresentar um algoritmo com este propósito. É analisada a seguir a interação entre os controles de fluxo END TO END e Local em uma cadeia de lances. Finalmente examina-se através de simulação, o comportamento de uma rede de computadores quando são aplicados os controles de fluxo END TO END e Local simultaneamente. / [en] In past years the importance of a method for selection of the window size in a computer network with End-to-End flow control hás been emphasized by several researchers. In this work, an algorithm is presented that perform this task. The analysis of the interaction between End-to-End flow control and Local flow control in a chain of links is also presented. Finally, using computer simulation, the behavior of a computer network when the End-to-End flow control and Local flow control are applied simultaneously is examined.

Early computerized health information systems supported applications in hospital records and laboratory data collection. Since that time, software has been developed for a number of health care providers such as doctors and pharmacists. Although local area networks are installed at larger institutions, only a few small-scale, special-purpose, wide-area networks are installed for external providers. To be adopted, wide-area networks should provide greater functionality than, and be cost-competitive with, conventional communication methods. Several projects are underway in Health Information Science to develop and evaluate generic, wide-area networks. This dissertation describes the design, analysis, development, implementation and evaluation of a prototype health care network which would be accessible to providers using existing computer equipment and the public switched telephone system. The network software, Health Link, supports reliable, automatic, store-and-forward messaging of medically-sensitive information. Encrypted messages can be authenticated and the software features registered delivery. An application programming interface formats messages in accordance with the HL7 data interchange standard. Simulation studies have been conducted which demonstrate the steady state characteristic behaviour of a node in a uniform cluster. Further studies have investigated a realistic, dynamic, large scale network. A peer-to-peer model and client-server model were analyzed and both were found to be feasible with respect to certain performance and cost criteria. The client-server model was found to be less costly to operate than the peer-to-peer model. The peer-to-peer model can transfer messages in a shorter time than the client-server model. The network software was verified in a field test involving four clinics, one medical laboratory, and one hospital. Data collected in the test provide performance benchmarks, an estimate of message sizes and frequencies, network reliability statistics, and a wealth of observations. Performance benchmarks and message traffic measurements were used to calibrate the simulation models. Results from this and other research indicate that, although most of the technical networking problems can be readily overcome, consensus on standards, health care applications, and initiatives should be promoted before a wide-spread, production network is implemented. / Graduate

Packet-switched wireless data networks built upon IP (Internet Protocol)-based infrastructure are being envisioned to provide ubiquitous Internet access to mobile users. Supporting packet-data services along with the cellular voice services in an integrated networking framework gives rise to new network infrastructure and protocol design issues that are to be resolved to facilitate the introduction of the next generation wireless IP networks. This thesis addresses several protocol design issues in the area of wireless packet data networking, namely, retransmission control design for multichannel protocols, radio link level protocol for dynamic rate and error control, inter-layer protocol dependency, radio link-layer and transport-layer protocol fairness and radio link-level dynamic bandwidth allocation. A retransmission control policy for a multichannel S-ALOHA (slotted ALOHA) protocol in a high speed wireless data network is proposed and analyzed. A sub-optimal dynamic rate adaptation procedure is proposed for uplink data transmission in WCDMA (Wideband Code Division Multiple Access)-based wireless IP networks. The performance of this scheme is analyzed using a novel ‘mean-sense’ approach for interference calculation in cellular WCDMA environment. The impact of macrodiversity packet combining on transport-protocol throughput performance is analyzed under different link-level retransmission control policies. A unified TDMA (Time Division Multiple Access)-based centralized bandwidth management mechanism is proposed as a link-level solution for providing service fairness among competing users for uplink data transmission in a wireless IP network. TCP (Transmission Control Protocol) performance is evaluated under different transport-level packet scheduling policies in a correlated fading environment and a time frame-based scheduling policy is proposed to provide service fairness among mobile users in the case of downlink transmission. A set of centralized burst-level bandwidth allocation policies are investigated as a means of service integration with QoS (Quality of Service) provisioning in the wireless IP air interface. / Graduate

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2005 / With the growth of the personal computer industry, a number of households now contain two or more personal computers. The need to share resources such as printers, scanners and other PC peripherals has become evident. Communication between personal computers and other smart devices in the home is also required. This brings the emergence of home networking together with home automation. Home networking is the collection of elements to enable the connection and integration of multiple computing, control and communication devices. There are various options at this stage for home networking. One of the broadband options is indoor power line communication. The aim of the project was to evaluate a communication system capable of performing efficiently in South African Home Power line environment. In designing a communication system capable of performing in the harsh conditions which are presented in the home environment (noise, attenuation, phase distortion, etc.), a mathematical model that is representative of a typical suburban South African home power line is required. To aid the modeling process, an experimental network was constructed so measurements could be taken in a controlled environment. In conjunction with simulation, the model of the home power line network has aided the design of the data communication system. The project has involved: • Determining optimal specifications for the communication system. • Development of a home power line model representative of a typical South African suburban home environment. • Construction and measurement of an experimental power grid • Development of methods, algorithms and programs for the design of an OFDM PLC modem (in software) to optimal specifications. • Simulation development in MA1LAB of the OFDM Modem. • Comparison of different OFDM sub-modulation schemes for enhancing the communication system performance, In conclusion, the simulation model of the PLC modem correlates well with typical practical systems. Optimising throughput of the communication system and hardware development of the modem will form the basis for further research.

Thesis (MTech (Business Administration))--Cape Peninsula University of Technology, 2011 / Online company registration is a service, which has been claimed by Congo-Brazzaville immigrant entrepreneurs. It has taken centuries for scientists to develop computers that successfully enable businesses to grow in an effective erasure of national frontiers for business purposes. B2B e-commerce, which heralded the dawn of globalisation in the EU, USA, India, New Zealand and South Africa, is not yet applicable in Congo- Brazzaville. Presently, B2B e-commerce has made the global economy porous, which consequently activated online business registration. This porosity has enabled SMMEs to save supply chain management costs, create jobs, improve customer care and contribute to the country’s GDP. However, owing to the characteristics of Congolese immigrants’ SMMEs in Cape Town, online business registration has become imperative to enable them to expand in Congo and to save supply chain management costs and contribute to the country’s economic reconstruction process. Recently, the Centre For Business and Administrative Procedures (CFBAP): Centre des Formalités Administratives des Entreprises’ (CFE) B2B e-commerce website has become in demand. Furthermore, at a national level, e-commerce website adoption at CFBAP will leverage the country’s standards of conducting business and will boost the pride of CFBAP, as an organisation, as well as its partners in an aspect that is at the core of its values. The main objective of this study is to analyse the benefits of online business registration for Congo-Brazzaville immigrant entrepreneurs in Cape Town. The study has established motivating factors to implement an e-commerce website at CFBAP in Brazzaville, but did not recommend any specific e-commerce technology for the institution. The research has also made an earnest attempt to illicit reasons why Congo-Brazzaville immigrant entrepreneurs invest in Brazzaville in spite of being well established in Cape Town. The research target population included Congo-Brazzaville immigrant entrepreneurs who were selected from their association and who live in Cape Town, where the study was conducted. The nature of the research dictated both quantitative and qualitative methodologies in order to gain a better understanding of the research problem that was identified. Key words: E-commerce, CFE, Congo-Brazzaville, World Bank, SMMEs, immigrants, Centre for Business and Administrative Procedures (CFBAP).

CAPES; CNPq / Este trabalho apresenta a implementação de um modelo do TCP-Reno, bem como uma técnica de modelamento de rede, detalhadamente apresentada, com o objetivo de mensurar a rajada e a vazão das conexões TCP compartilhadas em um roteador congestionado. Isso se faz necessário, para permitir estudar e prever o comportamento de uma rede. A validação do modelo implementado foi realizada por meio de comparações com resultados de simulações baseadas no software Network Simulator (NS-2). Posteriormente a apresentação do modelo, e como objetivo principal deste trabalho, foi feita uma análise detalhada de uma modificação no protocolo que implementa QoS (Quality of Service) na camada de transporte. Essa modificação no protocolo, denominada de TCP TS- Prio, implementa uma diferenciação no tamanho da janela deslizante, através de atribuição de prioridade para determinados fluxos. Essa análise revela as qualidades e limitações da utilização desse protocolo em cenários diferentes do original do TCP TS-Prio, onde o autor focava principalmente no comportamento dinâmico do protocolo. Como resultado do trabalho chega-se a conclusão de que o TCP TS-Prio é capaz de oferecer diferenciação de serviço, porém isto depende diretamente do estado de congestionamento da rede em questão. / This work presents the implementation of a model for the TCP-Reno protocol, as well as a detailed technique for modeling the network, with the purpose of measuring the burstiness and the throughput of TCP traffic in a congested shared router. This is necessary to study and to predict the behavior of a data network. The model was validated by comparing its results to simulations carried out with specialized simulation software, namely the Network Simulator (NS-2). After presenting the model and the main goals of this work, a detailed analysis of a modi- fied protocol that implements QoS (Quality of Service) in the transport layer was done. This protocol called TCP TS-Prio, implements a differentiation in the size of the sliding window, thus giving priorities to certain flows. This analysis is needed to reveal qualities and limitations of this protocol in several network environments (scenarios), because in the original work on TCP TS-Prio the author focused mainly on the dynamic behavior of the Protocol. We then conclude that TCP TS-Prio is able to offer service differentiation, but this depends directly on the network congestion degree. / 5000

CAPES; CNPq / Este trabalho apresenta a implementação de um modelo do TCP-Reno, bem como uma técnica de modelamento de rede, detalhadamente apresentada, com o objetivo de mensurar a rajada e a vazão das conexões TCP compartilhadas em um roteador congestionado. Isso se faz necessário, para permitir estudar e prever o comportamento de uma rede. A validação do modelo implementado foi realizada por meio de comparações com resultados de simulações baseadas no software Network Simulator (NS-2). Posteriormente a apresentação do modelo, e como objetivo principal deste trabalho, foi feita uma análise detalhada de uma modificação no protocolo que implementa QoS (Quality of Service) na camada de transporte. Essa modificação no protocolo, denominada de TCP TS- Prio, implementa uma diferenciação no tamanho da janela deslizante, através de atribuição de prioridade para determinados fluxos. Essa análise revela as qualidades e limitações da utilização desse protocolo em cenários diferentes do original do TCP TS-Prio, onde o autor focava principalmente no comportamento dinâmico do protocolo. Como resultado do trabalho chega-se a conclusão de que o TCP TS-Prio é capaz de oferecer diferenciação de serviço, porém isto depende diretamente do estado de congestionamento da rede em questão. / This work presents the implementation of a model for the TCP-Reno protocol, as well as a detailed technique for modeling the network, with the purpose of measuring the burstiness and the throughput of TCP traffic in a congested shared router. This is necessary to study and to predict the behavior of a data network. The model was validated by comparing its results to simulations carried out with specialized simulation software, namely the Network Simulator (NS-2). After presenting the model and the main goals of this work, a detailed analysis of a modi- fied protocol that implements QoS (Quality of Service) in the transport layer was done. This protocol called TCP TS-Prio, implements a differentiation in the size of the sliding window, thus giving priorities to certain flows. This analysis is needed to reveal qualities and limitations of this protocol in several network environments (scenarios), because in the original work on TCP TS-Prio the author focused mainly on the dynamic behavior of the Protocol. We then conclude that TCP TS-Prio is able to offer service differentiation, but this depends directly on the network congestion degree. / 5000

Information constitutes one of an organisation’s most valuable assets. It provides the modern organisation with a competitive edge and in some cases, is a requirement merely to survive. An organisation has to protect its information but due to the distributed, networked environment of today, faces a difficult challenge; it has to implement a system of information security management. Software applications can provide significant assistance in managing information security. They can be used to provide for centralised feedback of information security related activities as well as for centralised configuration activities. Such an application can be used in enforcing compliance to the organisation’s information security policy document. Currently there are a number of software products that provide this function in varying measures. In this research the major players in this space were examined to identify the features commonly found in these systems, and where they were lacking in terms of affordability, flexibility and scalability. A framework for an information security management application was defined based on these features and requirements and incorporating the idea of being affordable, but still flexible and extendable. This shifted the focus from attempting to provide a comprehensive list of interfaces and measurements into general information security related activities, to focusing on providing a generic tool that could be customised to handle any information fed back to it. The measurements could then be custom-developed as per the needs of the organisation. This formed the basis on which the prototype information security management application (InfoSure) was developed. / Prof. S.H. Solms

The twenty-first century has found education at the crossroads of change. There are burgeoning challenges facing the modern educator. To rise to the importuning, educators find themselves turning to Information Technology for the answers. The technologies utilised in attempts to overcome the challenges often include the Internet and electronic educational resources. Although the Internet is not unduly called the Information Highway, it is also fraught with misleading and incorrect information. Educators’ arduous searches result in few good and useable resources. Thus, to store, organise and efficiently retrieve the discovered resources is a matter of time-saving. The aim of the study was to develop a method to organise and retrieve educational resources in an efficient and personalised manner. In order to do this, an exploration into pedagogy and educational paradigms was undertaken. The current educational paradigm, constructivism, proposes that each learner is an individual with unique learning and personal needs. To develop a new model, the current models need to be understood. The current solutions for the organising of educational resources are realised as several software packages, also called e-learning packages. A list of criteria that describes the essential requirements for organising educational resources was established. These criteria were based upon the pedagogical principles prescribed by educators and the practical technological frameworks necessary to fulfil the needs of the teaching/learning situation. These criteria were utilised to critique and explore the available solutions. It was found that although the available e-learning packages fulfil a need within their genre, it does not meet with the core requirements of constructivism. The resource base model seeks to address these needs by focussing on the educational aspects of resource delivery over an Intranet. For the purposes of storing, organising and delivering the resources, a database had to be established. This database had to have numerous qualities, including the ability to search and retrieve resources with great efficiency. Retrieving data in an efficient manner is the forte of the star schema, while the storing and organising of data is the strength of a normalised schema. It is not standard practice to utilise both types of schemas within the same database. A star schema is usually reserved for data warehouses because of its data retrieval abilities. It is customary to utilise a normalised schema for operational databases. The resource base model, however, needs both the storage facilities of an operational database and the efficient query facilities of a data warehouse. The resource base model, therefore, melds both schemas into one database with interlinking tables. This database forms the foundation (or the back-end) of the resource base. The resource base model utilises web browsers as its user interface (or front-end). The results of the study on the pedagogy, the current e-learning solutions and the resource base were written up within this dissertation. The contribution that this dissertation makes is the development of a technique to efficiently store, organise and retrieve educational resources in such a manner that both the requirements of constructivism and outcomes-based education are fulfilled. To this end, a list of technological and pedagogical criteria on which to critique a resource delivery technique has been developed. This dissertation also elaborates on the schema designs chosen for the resource base, namely the normalised schema and the star schema. From this schema, a prototype has been developed. The prototype’s function was two-fold. The first function is to determine the feasibility of the technique. Secondly, to determine the success of the technique in fulfilling the needs expressed in the list of criteria