Dissertations / Theses on the topic 'Computer networks Packet switching (Data transmission) TCP/IP (Computer network protocol)'

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 58-61). Also available in electronic version. Access restricted to campus users.

Thesis (Ph.D.) -- University of Glasgow, 2001.
Includes bibliographical references (p.i-xv). Print version also available. Mode of access : World Wide Web. System requirments : Adobe Acrobat reader reuired to view PDF document.

O controle de congestionamento padrão do TCP apresenta vários problemas; ele não consegue distinguir se o pacote foi perdido por falha no enlace ou por descarte de pacotes devido a um congestionamento de rede (se a falha foi no enlace não há necessidade de ativar os mecanismos de controle de congestionamento); e o correto ajuste de sua taxa de transmissão requer informação de perdas de pacotes. Neste trabalho é apresentado o new generalized window advertising (NGWA), que é um novo esquema de controle de congestionamento para o TCP. O NGWA traz informações da banda disponível da infraestrutura de rede para os pontos finais da conexão TCP. Seu desempenho foi comparado com TCP New Reno, RED e o TCP padrão via simulações com o software NS-3, considerando topologias de rede largamente citadas na literatura. O NGWA foi, também, implementado e testado no Linux (versão 2.6.34). O novo método demonstrou ser superior aos comparados, apresentando uma operação mais estável, melhor justiça e menor taxa de perda de pacotes, considerando o elenco de testes realizados.
The TCP congestion control mechanism in standard implementations presents several problems; he cannot distinguish if the packet was lost by link failure or by congestion in the net (if the fault was in the link there is no need to active congestion control mechanisms); and the right adjust of your transmission rate requires information from packet loss. This work presents the new generalized window advertising (NGWA), which is a new congestion control scheme for TCP. The NGWA provides information considering the available bandwidth of the network infrastructure to the endpoints of the TCP connection. Results obtained by the NGWA approach were compared with those from TCP New Reno, RED, and standard TCP (using the network simulator NS-3), considering network topologies widely cited in the literature. A NGWA Linux implementation is also presented. The new method proved to be superior when compared with the traditional approaches, presenting a more stable operation, better fairness and lower packet loss, considering the set of tests carried out.

Orientador: Mauricio Ferreira Magalhães
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Dados a banda de transmissão atualmente disponível, o protocolo (IP) utilizado para transmitir a maior parte de tráfego e a quantidade de tráfego e seus requisitos de aos, a Engenharia de Tráfego (TE, de Traffic Engineering) tomou-se um componente cada vez mais importante nas redes de comunicações. O padrão do IETF para enncaminhamento roteamento entitulado Multi-Protocol Label Switching (MPLS) preenche lacunas importantes neste cenário e é peça chave das metodologias de TE mais sofisticadas. Nesta dissertação é apresentado um modelo genérico de TE e uma proposta para uma Plataforma para Experimentos com MPLS (PLEX MPLS) que permite que o usuário defina, execute, e analise configurações de Engenharia de Tráfego com MPLS em uma rede IP. Os principais objetivos da PLEX MPLS são: . Estudo da tecnologia MPLS e suporte a outros trabalhos em andamento no contexto do grupo de estudos em MPLS do DCA . Experimentos com engenharia de tráfego com MPLS: validação das tecnologias e conceitos relacionados . Experimentos didáticos em disciplinas de laboratório de redes. Os principais conceitos de TE e MPLS são apresentados como referência, bem como uma descrição do NIST Switch, a plataforma MPLS escolhida para este trabalho. A análise, projeto e implementação da PLEX MPLS são apresentados, pois formam parte significativa do trabalho desenvolvido. A PLEX não só utiliza, como também estende as funcionalidades oferecidas pelo NIST Switch a fim de oferecer um esquema de TE mais completo e eficiente. Na fase de análise, vemos quais os principais requisitos para a implementação desta plataforma, seguindo uma metodologia de Engenharia de Software. Na fase de projeto, vemos as soluções propostas para os problemas identificados na fase de análise e temos uma especificação dos componentes a serem implementados. Na fase seguinte, discutimos a implementação das principais características dos componentes da PLEX, justificando as decisões tomadas. Para validar a implementação da PLEX de acordo com sua proposta, foram realizados alguns experimentos em uma rede de testes com tráfego real. A execução destes experimentos é descrita e seus resultados analisados. Os resultados obtidos assinalam claramente a importância e utilidade de esquemas de TE baseada em MPLS. Uma interessante metodologia para TE, compilada a partir de várias propostas, é apresentada. Finalmente, apontam-se caminhos a seguir em um trabalho futuro de refinamento da PLEX
Abstract: Given the bandwidth currently available, the protocol (IP) used to transmit most Internet traffic, the quantity of traffic produced and its QoS requirements, Traffic Engineering (TE) has become an increasingly important component of communications networks. IETF's standard for forwarding/routing, which is entitled Multi-Protocol Label Switching (MPLS), presents important solutions in this scenario playing a major role in more sophisticated TE methodologies. This work presents a generic methodology for TE and a proposal for a Platform for Experiments with MPLS (PLEX MPLS) which allows the user to define, execute and analyze Traffic Engineering configurations with MPLS in an IP network. The main goals of PLEX MPLS are: . Study of the M PLS technology and support of other ongoing works with M PLS in the DCA . Traffic Engineering experiments with MPLS: validation of the related concepts and technologies . Support of didactic experiments in academic disciplines. The main concepts of MPLS and TE are presented as reference, as well as a brief description of NIST Switch, the MPLS software chosen for the PLEX MPLS implementation. The analysis, project and implementation of PLEX MPLS are presented, since are significant part of the developed work. PLEX not only uses, but also extends NIST Switch functionalities to offer a more complete and efficient TE scheme. In the analysis phase the main requirements for the PLEX implementation are specified, following a well-known Software Engineering methodology. The solutions found for the problems identified in the analysis phase are presented in the project phase alongside with a specification of the components that will be implemented. In the next phase, the implementation of PLEX is discussed focusing on the most important characteristics of PLEX components and justifying the implementation ecisions. In order to validate PLEX implementation and its proposal, some experiments were made in a test network with reallive traffic. These experiments are described and its results analyzed. The results obtained clearly indicate the importance and utility of TE schemes based on MPLS. Also an interesting TE methodology compiled from several proposals is presented. Finally, possible improvements and future work on PLEX MPLS are indicated.
Mestrado
Engenharia de Computação
Mestre em Engenharia Elétrica

In order to provide improved service quality to applications, networks need to address the need for reliability of data delivery. Reliability can be improved by incorporating fault tolerance into network routing, wherein a set of multiple routes are used for routing between a given source and destination. This thesis proposes a new fault-tolerant protocol, called the Multipath Fault Tolerant Protocol for Routing (MFTPR), to improve the reliability of network routing services. The protocol is based on a multipath discovery algorithm, the Quasi-Shortest Multipath (QSMP), and is designed to work in conjunction with the routing protocol employed by the network. MFTPR improves upon the QSMP algorithm by finding more routes than QSMP, and also provides for maintenance of these routes in the event of failure of network components. In order to evaluate the resilience of a pair of paths to failure, this thesis proposes metrics that evaluate the non-disjointness of a pair of paths and measure the probability of simultaneous failure of these paths. The performance of MFTPR to find alternate routes based on these metrics is analyzed through simulation.

Thesis (M.S.)--University of Florida, 2001.
Title from title page of source document. Document formatted into pages; contains vi, 78 p.; also contains graphics. Includes vita. Includes bibliographical references.

An increasing number of network applications use reliable transport protocols. Applications with constant data transmission recover from loss without major performance disruption, however, applications that send data sporadically, in small packets, also called thin-streams, experience frequently high latencies due to 'Bufferbloat', that reduce the application performance. Active Queue Management mechanisms were proposed to dynamically manage the queues in routers by dropping packets early and reduce these, hence reducing latency. While their deployment to the internet remains an open issue, the proper investigation into how their functioning mechanism impacts latency is the main focus of this work and research questions have been devised to investigate the AQM impact on latency. A range of AQM mechanisms has been evaluated by the research, exploring performance of the methods for latency sensitive network applications. This has explored new single queue AQM mechanisms such as Controlled Delay (CODEL) and Proportional Integral Enhanced (PIE) and Adaptive RED (ARED). The evaluation has shown great improvements in queuing latency when AQM are used over a range of network scenarios. Scheduling AQM algorithms such as FlowQueue CODEL (FQ-CODEL) isolates traffic and minimises the impact of Bufferbloat on flows. The core components of FQ-CODEL, still widely misunderstood at the time of its inception, have been explained in depth by this study and their contribution to reducing latency have been evaluated. The results show significant reductions in queuing latency for thin streams using FQ-CODEL. When TCP is used for thin streams, high application latencies can arise when there are retransmissions, for example after dropping packets by an AQM mechanism. This delay is a result of TCP's loss-based congestion control mechanism that controls sender transmission rate following packet loss. ECN, a marking sender-side improvement to TCP reduces applicationlayer latency without disrupting the overall network performance. The thesis evaluated the benefit of using ECN using a wide range of experiments. The findings show that FQ-CODEL with ECN provides a substantial reduction of application latency compared to a drop-based AQM. Moreover, this study recommends the combination of FQ-CODEL with other mechanisms, to reduce application latency. Mechanisms such as ABE, have been shown to increase aggregate throughput and reduce application latency for thin-stream applications.

In this paper we study packet delay and loss rate at the University of Fort Hare network. The focus of this paper is to evaluate the information derived from a multipoint measurement of, University of Fort Hare network which will be collected for a duration of three Months during June 2011 to August 2011 at the TSC uplink and Ethernet hubs outside and inside relative to the Internet firewall host. The specific value of this data set lies in the end to end instrumentation of all devices operating at the packet level, combined with the duration of observation. We will provide measures for the normal day−to−day operation of the University of fort hare network both at off-peak and during peak hours. We expect to show the impact of delay and loss rate at the University of Fort Hare network. The data set will include a number of areas, where service quality (delay and packet loss) is extreme, moderate, good and we will examine the causes and impacts on network users.

Active queue management (AQM) techniques for congestion control in Internet Protocol (IP) networks have been designed using both heuristic and analytical methods. But so far, there has been found no AQM scheme designed in the realm of stochastic optimization. Of the many options available in this arena, the gradient-based stochastic approximation method using Infintesimal Perturbation Analysis (IPA) gradient estimators within the Stochastic Fluid Model (SFM) framework is very promising. The research outlined in this thesis provides the theoretical basis and foundational layer for the development of IPA-based AQM schemes. Algorithms for computing the IPA gradient estimators for loss volume and queue workload were derived for the following cases: a single-stage queue with instantaneous, additive loss-feedback, a single-stage queue with instantaneous, additive loss-feedback and an unresponsive competing flow, a single-stage queue with delayed, additive loss-feedback, and a multi-stage tandem network of $m$ queues with instantaneous, additive loss-feedback. For all cases, the IPA gradient estimators were derived with the control parameter, $ heta$, being the buffer-limits of the queue(s). For the single-stage case and the multi-stage case with instantaneous, additive loss-feedback, the IPA gradient estimators for when the control parameter, $ heta$, is the loss-feedback constant, were also derived. Sensitivity analyses and optimizations were performed with control parameter, $ heta$, being the buffer-limits of the queue(s), as well as the loss-feedback constant.

Orientadores: Maurício Ferreira Magalhães, Christian Rodolfo Esteve Rothenberg
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Os roteadores atuais implementam uma arquitetura verticalmente integrada composta de uma camada de software e um hardware proprietários. Este modelo resulta em soluções de alto custo e inviabiliza a experimentação de novas idéias. Em contrapartida, existem alternativas de alta flexibilidade baseadas em software e, consequentemente, de baixo custo. Entretanto, essas soluções apresentam baixo desempenho. Motivado pela disponibilidade de uma API aberta para programação do plano de encaminhamento (ex. OpenFlow), esta dissertação apresenta uma proposta de arquitetura de roteamento IP com separação de planos. Trata-se de uma abordagem que procura combinar o alto desempenho de hardwares de prateleira (commodities) com a flexibilidade de uma pilha de roteamento executada remotamente em computadores de uso geral. O grande desafio é garantir confiabilidade, escalabilidade e desempenho à rede, a partir de um controle remoto e centralizado sobre uma arquitetura que permita maior flexibilidade no mapeamento entre os elementos de controle e encaminhamento. O resultado corresponde a uma nova proposta de roteamento IP com perspectivas promissoras do ponto de vista do custo e da flexibilidade. Com o objetivo de avaliar a arquitetura proposta foi desenvolvido um protótipo com base em uma versão simplificada do modelo. Os resultados da avaliação apresentados nesta dissertação comprovam a viabilidade da arquitetura
Abstract: Today's networking gear follows the model of computer mainframes, where closed source software runs on proprietary hardware. This approach results in expensive solutions and prevents equipment owners to put new ideas into practice. In contrast, recent alternatives of highly flexible softwarebased routers promise low cost and programmability at the expense of low performance. Motivated by the availability of an open API to control packet forwarding engines (i.e., OpenFlow), we propose a commodity IP routing architecture that combines the line-rate performance of commercial hardware with the flexibility of open source routing stacks (remotely) running on general-purpose computers. The challenge is to ensure reliability, scalability and performance to a network running a remote and centralized control plane architecture that allows a flexible mapping between the control and forwarding elements. The outcome is a novel point in the design space of cost-effective IP routing solutions with far-reaching implications. The initial experimental evaluation of our prototype implementation validates the feasibility of the design
Mestrado
Engenharia de Computação
Mestre em Engenharia Elétrica

Il lavoro è stato suddiviso in tre macro-aree. Una prima riguardante un'analisi teorica di come funzionano le intrusioni, di quali software vengono utilizzati per compierle, e di come proteggersi (usando i dispositivi che in termine generico si possono riconoscere come i firewall). Una seconda macro-area che analizza un'intrusione avvenuta dall'esterno verso dei server sensibili di una rete LAN. Questa analisi viene condotta sui file catturati dalle due interfacce di rete configurate in modalità promiscua su una sonda presente nella LAN. Le interfacce sono due per potersi interfacciare a due segmenti di LAN aventi due maschere di sotto-rete differenti. L'attacco viene analizzato mediante vari software. Si può infatti definire una terza parte del lavoro, la parte dove vengono analizzati i file catturati dalle due interfacce con i software che prima si occupano di analizzare i dati di contenuto completo, come Wireshark, poi dei software che si occupano di analizzare i dati di sessione che sono stati trattati con Argus, e infine i dati di tipo statistico che sono stati trattati con Ntop. Il penultimo capitolo, quello prima delle conclusioni, invece tratta l'installazione di Nagios, e la sua configurazione per il monitoraggio attraverso plugin dello spazio di disco rimanente su una macchina agent remota, e sui servizi MySql e DNS. Ovviamente Nagios può essere configurato per monitorare ogni tipo di servizio offerto sulla rete.

Siu Chun.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 66-68).
Abstracts in English and Chinese.
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Thesis Overview --- p.3
Chapter 2 --- Background and Related work --- p.4
Chapter 2.1 --- Emergence of IP-over-ATM --- p.4
Chapter 2.2 --- ATM architecture --- p.5
Chapter 2.3 --- Scheduling issues in output-queued switch --- p.6
Chapter 2.4 --- Scheduling issues in input-queued switch --- p.18
Chapter 3 --- The Deadline-ordered Burst-based Parallel Scheduling Strategy --- p.23
Chapter 3.1 --- Introduction --- p.23
Chapter 3.2 --- Switch and queueing model --- p.24
Chapter 3.2.1 --- Switch model --- p.24
Chapter 3.2.2 --- Queueing model --- p.25
Chapter 3.3 --- The DBPS Strategy --- p.26
Chapter 3.3.1 --- Motivation --- p.26
Chapter 3.3.2 --- Strategy --- p.31
Chapter 3.4 --- The Deadline-ordered Burst-based Parallel Iterative Matching --- p.33
Chapter 3.4.1 --- Algorithm --- p.34
Chapter 3.4.2 --- An example of DBPIM --- p.35
Chapter 3.5 --- Simulation results --- p.33
Chapter 3.6 --- Discussions --- p.46
Chapter 3.7 --- Future work --- p.47
Chapter 4 --- The Quasi-static DBPIM Algorithm --- p.50
Chapter 4.1 --- Introduction --- p.50
Chapter 4.2 --- Quasi-static path scheduling principle --- p.51
Chapter 4.3 --- Quasi-static DBPIM algorithm --- p.56
Chapter 4.4 --- An example of Quasi-static DBPIM --- p.59
Chapter 5 --- Conclusion --- p.63
Bibliography --- p.65

Zheng, Pengxuan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (leaves 53-57).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgments --- p.v
Table of Contents --- p.vi
List of Figures --- p.viii
List of Tables --- p.ix
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Motivation --- p.1
Chapter 1.2 --- Related Work --- p.2
Chapter 1.3 --- Our Contribution --- p.3
Chapter 1.4 --- Organization of the Thesis --- p.4
Chapter Chapter 2 --- Background Overview --- p.6
Chapter 2.1.1 --- Traditional Wireless Networks --- p.6
Chapter 2.2 --- Exponential Backoff --- p.7
Chapter 2.2.1 --- Introduction --- p.7
Chapter 2.2.2 --- Algorithm --- p.8
Chapter 2.2.3 --- Assumptions --- p.9
Chapter 2.3 --- System Description --- p.9
Chapter 2.3.1 --- MPR Capability --- p.9
Chapter 2.3.2 --- Backoff Slot --- p.10
Chapter 2.3.3 --- Carrier-sensing and Non-carrier-sensing Systems --- p.11
Chapter Chapter 3 --- Multipacket Reception in WLAN --- p.12
Chapter 3.1 --- MAC Protocol Description --- p.13
Chapter 3.2 --- Physical Layer Methodology --- p.16
Chapter 3.2.1 --- Blind RTS Separation --- p.17
Chapter 3.2.2 --- Data Packet Detection --- p.19
Chapter Chapter 4 --- Exponential Backoff with MPR --- p.21
Chapter 4.1 --- Analytical Model --- p.22
Chapter 4.1.1 --- Markov Model --- p.22
Chapter 4.1.2 --- Relations betweenpt andpc --- p.23
Chapter 4.2 --- Simulation Settings --- p.26
Chapter 4.3 --- Asymptotic Behavior of Exponential Backoff --- p.27
Chapter 4.3.1 --- Convergence ofpt andpc --- p.27
Chapter 4.3.2 --- Convergence of Npt --- p.29
Chapter Chapter 5 --- Non-carrier-sensing System --- p.31
Chapter 5.1 --- Performance Analysis --- p.31
Chapter 5.1.1 --- Throughput Derivation --- p.31
Chapter 5.1.2 --- Throughput Analysis --- p.32
Chapter 5.1.3 --- Convergence of S --- p.36
Chapter 5.2 --- Infinite Population Model --- p.38
Chapter 5.2.1 --- Attempt Rate --- p.38
Chapter 5.2.2 --- Asymptotic Throughput of Non-carrier-sensing System --- p.39
Chapter Chapter 6 --- Carrier-sensing System --- p.43
Chapter 6.1 --- Throughput Derivation --- p.43
Chapter 6.2 --- Asymptotic Behavior --- p.44
Chapter Chapter 7 --- General MPR Model --- p.48
Chapter Chapter 8 --- Conclusions --- p.51
Bibliography --- p.53

The emergence of portable terminals in work and living environments is accelerating the progression of wireless networks. A wireless ad hoc network is a new network concept where users establish peer-to-peer communication among themselves independently, in their small area. Since the wireless medium is a shared resource, it becomes an important design issue to efficiently allocate bandwidth among users. MAC (Medium Access Control) layer arbitrates the channel access to the wireless medium and is also responsible for bandwidth allocation to different users, therefore a large amount of research has been conducted on various MAC protocols for ad hoc wireless networks. This dissertation begins with a survey of existing wireless MAC protocols. The survey includes protocols designed for different network generations and topologies, classifying them based on architecture and mode of operation. Next, we concentrate on the MAC protocols proposed for distributed wireless networks. We propose a new MAC protocol based on a token-passing strategy; which not only incorporates the advantages of the guaranteed access scheme into the distributed type of wireless networks, but also the data rate and delay level QoS guarantees. Data rate QoS provides fairness into sharing of the channel, while delay level QoS introduces a flexible prioritized access to channels by adjusting transmission permission to the current network traffic activities. A simulation model for the protocol is developed and delay and throughput performance results are presented. To examine the efficiency and performance of the proposed MAC scheme in an ad hoc wireless environment, it is incorporated into the Bluetooth structured network. The model is then simulated in the Bluetooth environment and performance results are presented. Furthermore, an analytical model is proposed and an approximate delay analysis conducted for the proposed MAC scheme. Analytical results are derived and compared with results obtained from computer simulations. The dissertation concludes with suggestions for improvements and future work.
Thesis (M.Sc.-Engineering)-University of Natal, 2003.