120 research outputs found

    A SURVIVABLE DISTRIBUTED DATABASE AGAINST BYZANTINE FAILURE

    Get PDF
    Distributed Database Systems have been very useful technologies in making a wide range of information available to users across the World. However, there are now growing security concerns, arising from the use of distributed systems, particularly the ones attached to critical systems. More than ever before, data in distributed databases are more susceptible to attacks, failures or accidents owing to advanced knowledge explosions in network and database technologies. The imperfection of the existing security mechanisms coupled with the heightened and growing concerns for intrusion, attack, compromise or even failure owing to Byzantine failure are also contributing factors. The importance of  survivable distributed databases in the face of byzantine failure, to other emerging technologies is the motivation for this research. Furthermore, It has been observed that most of the existing works on distributed database only dwelled on maintaining data integrity and availability in the face of attack. There exist few on availability or survibability of distributed databases owing to internal factors such as internal sabotage or storage defects. In this paper, an architecture for entrenching survivability of Distributed Databases occasioned by Byzantine failures is proposed. The proposed architecture concept is based on re-creating data on failing database server based on a set  threshold value.The proposed architecture is tested and found to be capable of improving probability of survivability in distributed database where it is implemented to  99.6%  from 99.2%.

    Energy Efficient IP over WDM Networks Using Network Coding

    Get PDF
    In this thesis we propose the use of network coding to improve the energy efficiency in core networks, by reducing the resources required to process traffic flows at intermediate nodes. We study the energy efficiency of the proposed scheme through three approaches: (i) developing a mixed integer linear programme (MILP) to optimise the use of network resources. (ii) developing a heuristic based on minimum hop routing. (iii) deriving an analytical bounds and closed form expressions. The results of the MILP model show that implementing network coding over typical networks can introduce savings up to 33% compared to the conventional architectures. The results of the heuristic show that the energy efficient minimum hop routing in network coding enabled networks achieves power savings approaching those of the MILP model. The analytically calculated power savings also confirm the savings achieved by the model. Furthermore, we study the impact of network topology on the savings obtained by implementing network coding. The results show that the savings increase as the hop count of the network topology increases. Using the derived expressions, we calculated the maximum power savings for regular topologies as the number of nodes grows. The power savings asymptotically approach 45% and 23% for the ring (and line) and star topology, respectively. We also investigate the use of network coding in 1+1 survivable IP over WDM networks. We study the energy efficiency of this scheme through MILP, a heuristic with five operating options, and analytical bounds. We evaluate the MILP and the heuristics on typical and regular network topologies. Implementing network coding can produce savings up to 37% on the ring topology and 23% considering typical topologies. We also study the impact of varying the demand volumes on the network coding performance. We also develop analytical bounds for the conventional 1+1 protection and the 1+1 with network coding to verify the results of the MILP and the heuristics and study the impact of topology, focusing on the full mesh and ring topologies, providing a detailed analysis considering the impact of the network size

    Implementation of linear network coding over a flexible emulator

    Get PDF
    This dissertation has the main objective of study and implement network coding (NC) techniques in a flexible emulator, programmed in a language that allows the coexistence of entities running parallel code, in order to emulate each node independently. The dissertation starts with the study of NC’s concept and with the characterization of the different type of coding methods, with a focus on linear network coding (LNC). . A flexible Java emulator (named Net Genius) was developed, which not only allows numerous topologies of networks, but also different types of coding. In addition, the emulator allows to emulate the networks in two different modes: with a distributed network or with a centralized network. In order to present the differences between the LNC approach and the traditional approach used in packet networks (based in routing tables), the emulator allows the user to choose between these two types of approach, assessing the impact of having network coding over user-defined networks. When implementing LNC, the concept of generations of packets was introduced in order to avoid combining packets from different sources. Leveraging on this, the transfer matrix at each node is calculated based on the coded packets and not based on the information stored in each node. In addition to this, a mechanism to code packets at the source was implemented, as well as a mechanism to introduce errors in the connection links. This allowed to emulate networks with different link error probabilities, in order to assess the resilience of the different approaches to the presence of failures.Esta dissertação visa estudar e a implementar técnicas de network coding (NC) num emulador flexível, programado numa linguagem que permita a coexistência de entidades a correr código em paralelo por forma a simular cada nó de forma independente. Este trabalho começa com estudo do conceito de NC e da caracterização dos diferentes tipos de métodos de codificação, focando-nos essencialmente no linear network coding (LNC). Optou-se por criar um emulador flexível em Java (designado por Net Genius), que não só permite várias topologias de redes, mas também vários tipos de codificação. Além disso, o emulador permite emular as redes em dois modos diferentes, um modo com uma rede distribuída e outro com uma rede centralizada. De modo a evidenciar as diferenças entre a abordagem LNC e a abordagem tradicional (sem codificação), o emulador permite escolher o tipo de abordagem em cada emulação, o que permite estudar o impacto do NC em redes definidas por utilizadores. Procedeu-se à implementação de técnicas LNC e introduziu-se um conceito de gerações de pacotes, de modo a evitar a codificação de pacotes de diferentes fontes. A par disto, a matriz de codificação é calculada com base nos pacotes codificados e não com base na informação guardada em cada nó. Por último, implementou-se um mecanismo para codificação de pacotes na fonte e um mecanismo de introdução de erros nos links, permitindo emular a rede com diferentes probabilidades de erro, sendo possível ver como as abordagens resistem à existência de falhas nas ligações

    Journal of Telecommunications and Information Technology, 2010, nr 2

    Get PDF
    kwartalni

    Libraries as Life-Systems: Information, Entropy, and Coevolution on Campus

    Get PDF
    published or submitted for publicatio

    Application acceleration for wireless and mobile data networks

    Get PDF
    This work studies application acceleration for wireless and mobile data networks. The problem of accelerating application can be addressed along multiple dimensions. The first dimension is advanced network protocol design, i.e., optimizing underlying network protocols, particulary transport layer protocol and link layer protocol. Despite advanced network protocol design, in this work we observe that certain application behaviors can fundamentally limit the performance achievable when operating over wireless and mobile data networks. The performance difference is caused by the complex application behaviors of these non-FTP applications. Explicitly dealing with application behaviors can improve application performance for new environments. Along this overcoming application behavior dimension, we accelerate applications by studying specific types of applications including Client-server, Peer-to-peer and Location-based applications. In exploring along this dimension, we identify a set of application behaviors that significantly affect application performance. To accommodate these application behaviors, we firstly extract general design principles that can apply to any applications whenever possible. These design principles can also be integrated into new application designs. We also consider specific applications by applying these design principles and build prototypes to demonstrate the effectiveness of the solutions. In the context of application acceleration, even though all the challenges belong to the two aforementioned dimensions of advanced network protocol design and overcoming application behavior are addressed, application performance can still be limited by the underlying network capability, particularly physical bandwidth. In this work, we study the possibility of speeding up data delivery by eliminating traffic redundancy present in application traffics. Specifically, we first study the traffic redundancy along multiple dimensions using traces obtained from multiple real wireless network deployments. Based on the insights obtained from the analysis, we propose Wireless Memory (WM), a two-ended AP-client solution to effectively exploit traffic redundancy in wireless and mobile environments. Application acceleration can be achieved along two other dimensions: network provision ing and quality of service (QoS). Network provisioning allocates network resources such as physical bandwidth or wireless spectrum, while QoS provides different priority to different applications, users, or data flows. These two dimensions have their respective limitations in the context of application acceleration. In this work, we focus on the two dimensions of overcoming application behavior and Eliminating traffic redundancy to improve application performance. The contribution of this work is as follows. First, we study the problem of application acceleration for wireless and mobile data networks, and we characterize the dimensions along which to address the problem. Second, we identify that application behaviors can significantly affect application performance, and we propose a set of design principles to deal with the behaviors. We also build prototypes to conduct system research. Third, we consider traffic redundancy elimination and propose a wireless memory approach.Ph.D.Committee Chair: Sivakumar, Raghupathy; Committee Member: Ammar, Mostafa; Committee Member: Fekri, Faramarz; Committee Member: Ji, Chuanyi; Committee Member: Ramachandran, Umakishor

    What is an internet? Norbert Wiener and the society of control

    Get PDF
    By means of a philosophical reading of Norbert Wiener, founder of cybernetics, this thesis attempts to derive anew the concepts of internet and control. It develops upon Wiener’s position that every age is reflected by a certain machine, arguing that the internet is that which does so today. Grounded by a critical historiography of the relation between the Cold War and the internet’s invention in 1969 by the ‘network’ of J. C. R. Licklider, it argues for an agonistic concept of internet derived from Wiener’s disjunctive reading of figures including Claude Bernard, Walter Cannon, Benoît Mandelbrot, John von Neumann and above all, his Neo-Kantian inflected reading of Leibniz. It offers a counter-theory of the society of control to those grounded by Spinoza’s ethology, notably that of Michael Hardt and Toni Negri, and attempts to establish a single conceptual vocabulary for depicting the possible modes of conflict through which an internet is determined

    Serving the nation for fifty years: 1952 - 2002 Lawrence Livermore National Laboratory, fifty years of accomplishments

    Full text link
    corecore