215 research outputs found

    Internet Message Access Protocol - Version 4rev1

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    PERFORMANCE CHARACTERISATION OF IP NETWORKS

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    The initial rapid expansion of the Internet, in terms of complexity and number of hosts, was followed by an increased interest in its overall parameters and the quality the network offers. This growth has led, in the first instance, to extensive research in the area of network monitoring, in order to better understand the characteristics of the current Internet. In parallel, studies were made in the area of protocol performance modelling, aiming to estimate the performance of various Internet applications. A key goal of this research project was the analysis of current Internet traffic performance from a dual perspective: monitoring and prediction. In order to achieve this, the study has three main phases. It starts by describing the relationship between data transfer performance and network conditions, a relationship that proves to be critical when studying application performance. The next phase proposes a novel architecture of inferring network conditions and transfer parameters using captured traffic analysis. The final phase describes a novel alternative to current TCP (Transmission Control Protocol) models, which provides the relationship between network, data transfer, and client characteristics on one side, and the resulting TCP performance on the other, while accounting for the features of current Internet transfers. The proposed inference analysis method for network and transfer parameters uses online nonintrusive monitoring of captured traffic from a single point. This technique overcomes limitations of prior approaches that are typically geared towards intrusive and/or dual-point offline analysis. The method includes several novel aspects, such as TCP timestamp analysis, which allows bottleneck bandwidth inference and more accurate receiver-based parameter measurement, which are not possible using traditional acknowledgment-based inference. The the results of the traffic analysis determine the location of the eventual degradations in network conditions relative to the position of the monitoring point. The proposed monitoring framework infers the performance parameters of network paths conditions transited by the analysed traffic, subject to the position of the monitoring point, and it can be used as a starting point in pro-active network management. The TCP performance prediction model is based on the observation that current, potentially unknown, TCP implementations, as well as connection characteristics, are too complex for a mathematical model. The model proposed in this thesis uses an artificial intelligence-based analysis method to establish the relationship between the parameters that influence the evolution of the TCP transfers and the resulting performance of those transfers. Based on preliminary tests of classification and function approximation algorithms, a neural network analysis approach was preferred due to its prediction accuracy. Both the monitoring method and the prediction model are validated using a combination of traffic traces, ranging from synthetic transfers / environments, produced using a network simulator/emulator, to traces produced using a script-based, controlled client and uncontrolled traces, both using real Internet traffic. The validation tests indicate that the proposed approaches provide better accuracy in terms of inferring network conditions and predicting transfer performance in comparison with previous methods. The non-intrusive analysis of the real network traces provides comprehensive information on the current Internet characteristics, indicating low-loss, low-delay, and high-bottleneck bandwidth conditions for the majority of the studied paths. Overall, this study provides a method for inferring the characteristics of Internet paths based on traffic analysis, an efficient methodology for predicting TCP transfer performance, and a firm basis for future research in the areas of traffic analysis and performance modelling

    IPv6: a new security challenge

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    Tese de mestrado em Segurança Informática, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2011O Protocolo de Internet versão 6 (IPv6) foi desenvolvido com o intuito de resolver alguns dos problemas não endereçados pelo seu antecessor, o Protocolo de Internet versão 4 (IPv4), nomeadamente questões relacionadas com segurança e com o espaço de endereçamento disponível. São muitos os que na última década têm desenvolvido estudos sobre os investimentos necessários à sua adoção e sobre qual o momento certo para que o mesmo seja adotado por todos os players no mercado. Recentemente, o problema da extinção de endereçamentos públicos a ser disponibilizado pelas diversas Region Internet registry – RIRs - despertou o conjunto de entidades envolvidas para que se agilizasse o processo de migração do IPv4 para o IPv6. Ao contrário do IPv4, esta nova versão considera a segurança como um objetivo fundamental na sua implementação, nesse sentido é recomendado o uso do protocolo IPsec ao nível da camada de rede. No entanto, e devido à imaturidade do protocolo e à complexidade que este período de transição comporta, existem inúmeras implicações de segurança que devem ser consideradas neste período de migração. O objetivo principal deste trabalho é definir um conjunto de boas práticas no âmbito da segurança na implementação do IPv6 que possa ser utilizado pelos administradores de redes de dados e pelas equipas de segurança dos diversos players no mercado. Nesta fase de transição, é de todo útil e conveniente contribuir de forma eficiente na interpretação dos pontos fortes deste novo protocolo assim como nas vulnerabilidades a ele associadas.IPv6 was developed to address the exhaustion of IPv4 addresses, but has not yet seen global deployment. Recent trends are now finally changing this picture and IPv6 is expected to take off soon. Contrary to the original, this new version of the Internet Protocol has security as a design goal, for example with its mandatory support for network layer security. However, due to the immaturity of the protocol and the complexity of the transition period, there are several security implications that have to be considered when deploying IPv6. In this project, our goal is to define a set of best practices for IPv6 Security that could be used by IT staff and network administrators within an Internet Service Provider. To this end, an assessment of some of the available security techniques for IPv6 will be made by means of a set of laboratory experiments using real equipment from an Internet Service Provider in Portugal. As the transition for IPv6 seems inevitable this work can help ISPs in understanding the threats that exist in IPv6 networks and some of the prophylactic measures available, by offering recommendations to protect internal as well as customers’ networks

    Computer Science Principles with Java

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    This textbook is intended to be used for a first course in computer science, such as the College Board’s Advanced Placement course known as AP Computer Science Principles (CSP). This book includes all the topics on the CSP exam, plus some additional topics. It takes a breadth-first approach, with an emphasis on the principles which form the foundation for hardware and software. No prior experience with programming should be required to use this book. This version of the book uses the Java programming language.https://rdw.rowan.edu/oer/1018/thumbnail.jp

    A platform for distributed learning and teaching of algorithmic concepts

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    Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 119-121).by Nathan D.T. Boyd.M.Eng

    Internet Key Exchange Protocol Version 2 (IKEv2)

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    Computer Science Principles with Python

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    This textbook is intended to be used for a first course in computer science, such as the College Board’s Advanced Placement course known as AP Computer Science Principles (CSP). This book includes all the topics on the CSP exam, plus some additional topics. It takes a breadth-first approach, with an emphasis on the principles which form the foundation for hardware and software. No prior experience with programming should be required to use this book. This version of the book uses the Python programming language.https://rdw.rowan.edu/oer/1024/thumbnail.jp

    Computer Science Principles with C++

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    This textbook is intended to be used for a first course in computer science, such as the College Board’s Advanced Placement course known as AP Computer Science Principles (CSP). This book includes all the topics on the CSP exam, plus some additional topics. It takes a breadth-first approach, with an emphasis on the principles which form the foundation for hardware and software. No prior experience with programming should be required to use this book. This version of the book uses the C++ programming language.https://rdw.rowan.edu/oer/1025/thumbnail.jp

    Compound popular content caching strategy to enhance the cache management performance in named data networking

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    Named Data Networking (NDN) is a leading research paradigm for the future Internet architecture. The NDN offers in-network cache which is the most beneficial feature to reduce the difficulties of the location-based Internet paradigm. The objective of cache is to achieve a scalable, effective, and consistent distribution of information. However, the main issue which NDN facing is the selection of appropriate router during the content’s transmission that can disrupt the overall network performance. The reason is that how each router takes a decision to the cache which content needs to cache at what location that can enhance the complete caching performance. Therefore, several cache management strategies have been developed. Still, it is not clear which caching strategy is the most ideal for each situation. This study proposes a new cache management strategy named as Compound Popular Content Caching Strategy (CPCCS) to minimize cache redundancy with enhanced diversity ratio and improving the accessibility of cached content by providing short stretch paths. The CPCCS was developed by combining two mechanisms named as Compound Popular Content Selection (CPCS) and Compound Popular Content Caching (CPCC) to differentiate the contents regarding their Interest frequencies using dynamic threshold and to find the best possible caching positions respectively. CPCCS is compared with other NDN-based caching strategies, such as Max-Gain In-network Caching, WAVE popularity-based caching strategy, Hop-based Probabilistic Caching, Leaf Popular Down, Most Popular Cache, and Cache Capacity Aware Caching in a simulation environment. The results show that the CPCCS performs better in which the diversity and cache hit ratio are increased by 34% and 14% respectively. In addition, the redundancy and path stretch are decreased by 44% and 46% respectively. The outcomes showed that the CPCCS have achieved enhanced caching performance with respect to different cache size (1GB to 10GB) and simulation parameters than other caching strategies. Thus, CPCCS can be applicable in future for the NDN-based emerging technologies such as Internet of Things, fog and edge computing
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