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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Situation-aware routing for wireless mesh networks with mobile nodes

Kobo,Hlabishi January 2012 (has links)
No description available.

Situation-aware routing for wireless mesh networks with mobile nodes

Kobo,Hlabishi January 2012 (has links)
No description available.


Hsieh, Chin-Nan 27 July 2001 (has links)


Chen, Yu-Lin 27 July 2001 (has links)

Impact of network security on SDN controller performance

Kodzai, Carlton January 2020 (has links)
Internet Protocol network architectures are gradually evolving from legacy flat networks to new modern software defined networking approaches. This evolution is crucial as it provides the ideal supporting network structure, architecture and framework that supports the technologies that are also evolving in software-based systems like Network Functions Virtualization (NFV). The connectivity requirements resulting from this paradigm shift in technology is being driven by new bandwidth requirements emanating from the huge number of new use cases from 5G networks and Internet of things (IoT) future technologies. Network security remains a key critical requirement of these new modern network architectures to deliver a highly available, reliable service and guaranteed quality of service. Unprotected networks will usually experience service interruptions and cases of system non-availability due to network attacks such as denial-of services and virus attacks which can render key network components unusable or totally unavailable. With the centralized approach of the Software Defined Networking architecture, the SDN controller becomes a key network point that is susceptible to internal and external attacks from hackers and many forms of network breaches. It being the heart of the SDN network makes it a single point of failure and it is crucial that the security of the controller is guaranteed to avoid unnecessary irrecoverable loss of valuable production time, data and money. The SDN controller design should be guided by a robust security policy framework with a very sound remedy and business continuity plan in the event of any form of a security attack. Security designs and research work in SDN controllers have been done with focus on achieving the most reliable and scalable platforms through self-healing and replication processes. In this dissertation the research that was done proposed a security solution for the SDN controller and evaluated the impact of the security solution on the overall SDN controller performance. As part of the research work literature review of the SDN controller and related technology carried out. The SDN controller interfaces were analyzed and the security threats that attack interfaces were explored. With link to a robust security framework a security solution was used in the experiments that analyzed the attacks from the external network sources which focused on securing the southbound interface by use of a netfilter with iptables firewall on the SDN controller. The SDN controller was subjected to denial service attack packets and the impact of the mitigation action observed on the SDN controller resources. Given that the network security layer introduced an additional overhead on the SDN controller's processors the security feature negatively affected the controller performance. The impact of the security overhead will inform on the future designs and possibly achieve a trade-off point between the level of security of the network and overall system performance due to security policies. The research analyzed and determined the performance impact of this crucial design aspect and how the additional loading due to network security affected the SDN controller normal operation.

Improving network routing performance in dynamic environments

Liu, Yong 25 April 2007 (has links)
In this dissertation, we study methods for improving the routing performance of computer communication networks in dynamic environments. The dynamic environments we considered in this work include both network topology changes and traffic demand changes. In the first part, We propose a novel fast rerouting scheme for link state routing protocols. Link state routing protocols are widely used by today’s ISPs on their backbone networks. The global update based rerouting of link state protocols usually takes seconds to complete which affects real time applications like Voice over IP. In our scheme, usually, only routers directly connected to failed links are involved in rerouting. For other cases, only a small number of neighboring routers are also involved. Since our scheme calculates rerouting paths in advance, rerouting can be done faster than previous reactive approaches. The computation complexity of our scheme is less than previous proactive approaches. In the second part, we study Multihoming Route Control (MRC) that is a technology used by multihomed stub networks recently. By selecting ISPs with better quality, MRC can improve routing performance of stub networks significantly. We first study the stability issue of distributed MRC and propose two methods to avoid possible oscillations of traditional MRC. The first MRC method is based on “optimal routing”. The idea is to let the stub networks belonging to a same organization coordinate their MRC and thus avoid oscillations. The second method is based on “user-optimal routing”. The idea is to allow MRC devices to use multiple paths for traffic to one destination network and switch traffic between paths smoothly when path quality or the traffic matrix changes. A third MRC method we propose is for MRC of traffic consisting of TCP flows of different sizes on paths with bottlenecks of limited capacity. Based on analysis of quality characteristics of bottleneck links, we propose a greedy MRC approach that works in small timescales. Simulation results show that the proposed MRC method can greatly improve routing performance for the MRC sites as well as the overall routing performance of all sites in the network.

An analysis of voice over Internet Protocol in wireless mesh networks

Meeran, Mohammad Tariq January 2012 (has links)
<p>This thesis presents an analysis of the impact of node mobility on the quality of service for voice over Internet Protocol in wireless mesh networks. Voice traffic was simulated on such a mesh&nbsp / network to analyze the following performance metrics: delay, jitter, packet loss and throughput. Wireless mesh networks present interesting characteristics such as multi-hop routing, node mobility, and variable coverage that can impact on quality of service. A reasonable deployment scenario for a small organizational network, for either urban or rural deployment, is considered with three wireless mesh network scenarios, each with 26 mesh nodes. In the first scenario, all mesh nodes are stationary. In the second scenario, 10 nodes are mobile and 16 nodes are stationary.&nbsp / Finally, in the third scenario, all mesh nodes are mobile. The mesh nodes are simulated to move at a walking speed of 1.3m per second. The results show that node mobility can increase packet&nbsp / loss, delay, and jitter. However, the results also show that wireless mesh networks can provide acceptable quality of service, providing that there is little or no background traffic generated by other&nbsp / applications. In particular, the results demonstrate that jitter across all scenarios remains within humanacceptable tolerances. It is therefore recommended that voice over Internet Protocol implementations on wireless mesh networks with background traffic be supported by quality of service standards / otherwise they can lead to service delivery failures. On the other hand, voice-only&nbsp / esh networks, even with mobile nodes, offer an attractive alternative voice over Internet Protocol platform. </p>

Decision Support Systems: Diagnostics and Explanation methods : In the context of telecommunication networks

Lindberg, Martin January 2013 (has links)
This thesis work, conducted at Ericsson Software Research, aims to recommend a system setup for a tool to help troubleshooting personal at network operation centres (NOC) who monitors the telecom network. This thesis examines several different artificial intelligence algorithms resulting in the conclusion that Bayesian networks are suitable for the aimed system. Since the system will act as a decision support system it needs to be able to explain how recommendations have been developed. Hence a number of explanation methods have been examined. Unfortunately no satisfactory method was found and thus a new method was defined, modified explanation tree (MET) which visually illustrates the variables of most interest in a so called tree structure. The method was implementation and after some initial testing the method has gained some positive first feedback from stakeholders. Thus the final recommendation consists of a system based on a Bayesian model where the gathered training data is collected earlier from the domain. The users will thus obtain recommendations for the top ranked cases and afterwards get the option to get further explanation regarding the specific cause. The explanation aims to give the user situation awareness and help him/her in the final action to solve the problem.

Connect street light control devices in a secure network

Lykouropoulos, Efstathios, Kostoulas, Andreas, Jumaa, Zainab January 2015 (has links)
Wireless communications is a constantly progressing technology in network engineering society, creating an environment full of opportunities that are targeting in financial growth, quality of life and humans prosperity. Wireless security is the science that has as a goal to provide safe data communication between authorized users and prevent unauthorized users from gaining access, deny access, damage or counterfeit data in a wireless environment. In order to success it uses layers of protection that consist of software and hardware mechanisms that are able to monitor network’s behavior and in coordination provide a safe and secure environment for the user. In this thesis, a scientific research will be conducted in a given wireless network topology designed for an original application. This is about an intelligent street lightning system and it has already been implemented by Greinon Engineering which is the company that we are cooperating with. It is a matter of great importance that this thesis was conducted under real life criteria and in cooperation with an engineering company. This means that our programming, our ideas, our study research were all rotated and concentrated in certain type of hardware – software and network topology. In this thesis there is a detailed overview of basic wireless security mechanisms – vulnerabilities – types of attacks and countermeasures focused on 802.11b protocol. Moreover there will be security weak point’s analysis on the given industrial network; our proposals to protect and secure this network based on our threat analysis of the current system. There is an analysis on the most up to date VPN security implementations and reasoning that guided our team to conclude in a specific procedure - protocol and implementation, including limitation factors – obstacles faces during this procedure. During this research iterative approach in procedures – ideas and implementation attempts is followed. Basic goal is to provide security solutions that are easy applicable, low cost, easy to maintain and monitor.

Vertical motion control of twin-hull vessels in regular head seas using a neural optimal controller

Kenevissi, Farhad January 2000 (has links)
No description available.

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