663 research outputs found
Modelação e simulação de equipamentos de rede para Indústria 4.0
Currently, the industrial sector has increasingly opted for digital technologies
in order to automate all its processes. This development comes from
notions like Industry 4.0 that redefines the way these systems are designed.
Structurally, all the components of these systems are connected in a complex
network known as the Industrial Internet of Things. Certain requirements
arise from this concept regarding industrial communication networks. Among
them, the need to ensure real-time communications, as well as support for
dynamic resource management, are extremely relevant. Several research
lines pursued to develop network technologies capable of meeting such
requirements. One of these protocols is the Hard Real-Time Ethernet Switch
(HaRTES), an Ethernet switch with support for real-time communications and
dynamic resource management, requirements imposed by Industry 4.0.
The process of designing and implementing industrial networks can,
however, be quite time consuming and costly. These aspects impose
limitations on testing large networks, whose level of complexity is higher and
requires the usage of more hardware. The utilization of network simulators
stems from the necessity to overcome such restrictions and provide tools to
facilitate the development of new protocols and evaluation of communications
networks.
In the scope of this dissertation a HaRTES switch model was developed
in the OMNeT++ simulation environment. In order to demonstrate a
solution that can be employed in industrial real-time networks, this dissertation
presents the fundamental aspects of the implemented model as well as a set
of experiments that compare it with an existing laboratory prototype, with the
objective of validating its implementation.Atualmente o setor industrial tem vindo cada vez mais a optar por tecnologias
digitais de forma a automatizar todos os seus processos. Este desenvolvimento
surge de noções como Indústria 4.0, que redefine o modo de como
estes sistemas são projetados. Estruturalmente, todos os componentes
destes sistemas encontram-se conectados numa rede complexa conhecida
como Internet Industrial das Coisas. Certos requisitos advêm deste conceito,
no que toca às redes de comunicação industriais, entre os quais se destacam
a necessidade de garantir comunicações tempo-real bem como suporte a
uma gestão dinâmica dos recursos, os quais são de extrema importância.
Várias linhas de investigação procuraram desenvolver tecnologias de rede
capazes de satisfazer tais exigências. Uma destas soluções é o "Hard
Real-Time Ethernet Switch" (HaRTES), um switch Ethernet com suporte a
comunicações de tempo-real e gestão dinâmica de Qualidade-de-Serviço
(QoS), requisitos impostos pela Indústria 4.0.
O processo de projeto e implementação de redes industriais pode, no
entanto, ser bastante moroso e dispendioso. Tais aspetos impõem limitações
no teste de redes de largas dimensões, cujo nível de complexidade é
mais elevado e requer o uso de mais hardware. Os simuladores de redes
permitem atenuar o impacto de tais limitações, disponibilizando ferramentas
que facilitam o desenvolvimento de novos protocolos e a avaliação de redes
de comunicações.
No âmbito desta dissertação desenvolveu-se um modelo do switch HaRTES
no ambiente de simulação OMNeT++. Com um objetivo de demonstrar uma
solução que possa ser utilizada em redes de tempo-real industriais, esta
dissertação apresenta os aspetos fundamentais do modelo implementado
bem como um conjunto de experiências que o comparam com um protótipo
laboratorial já existente, no âmbito da sua validação.Mestrado em Engenharia Eletrónica e Telecomunicaçõe
Simulation and Evaluation of Wired and Wireless Networks with NS2, NS3 and OMNET++
Communication systems are emerging rapidly with the revolutionary growth in terms of networking protocols, wired and wireless technologies, user applications and other IEEE standards. Numbers of industrial as well as academic organizations around the globe are bringing in light new innovations and ideas in the field of communication systems. These innovations and ideas require intense evaluation at initial phases of development with the use of real systems in place. Usually the real systems are expensive and not affordable for the evaluation. In this case, network simulators provide a complete cost-effective testbed for the simulation and evaluation of the underlined innovations and ideas. In past, numerous studies were conducted for the performance evaluation of network simulators based on CPU and memory utilization. However, performance evaluation based on other metrics such as congestion window, throughput, delay, packet delivery ratio and packet loss ratio was not conducted intensively. In this thesis, network simulators such as NS2, NS3 and OMNET++ will be evaluated and compared for wired and wireless networks based on congestion window, throughput, delay, packet delivery and packet loss ratio. In the theoretical part, information will be provided about the wired and wireless networks and mathematical interpretation of various components used for these networks. Furthermore, technical details about the network simulators will be presented including architectural design, programming languages and platform libraries. Advantages and disadvantages of these network simulators will also be highlighted. In the last part, the details about the experiments and analysis conducted for wired and wireless networks will be provided. At the end, findings will be concluded and future prospects of the study will be advised.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
SCTP - Evaluating, Improving and Extending the Protocol for Broader Deployment
Zugriff auf den Volltext ist gesperrt, neue Version unter DuEPublico-ID 35000
The Stream Control Transmission Protocol (SCTP), originally designed for
the transport of signaling messages over IP based telephony signaling networks,
is a general transport protocol with features suitable for a variety
of applications that can benefit from multihoming, multiple streams, or one
of SCTP’s numerous extensions. To date, SCTP has found its way into all
kernel implementations of UNIX derivatives and a Windows prototype, but
there are still flaws, which have to be identified and corrected.
In this thesis, first, a suite of tools consisting of an SCTP simulation and
testing environment is provided to lay the groundwork for further studies.
Starting from comparing and analyzing kernel implementations, several aspects
of the protocol that lead to undesirable behavior are examined. Congestion
and flow control that are adopted from the Transmission Control
Protocol (TCP), although using the same mechanisms, need a special treatment
because of SCTP’s message orientation. The analysis of the SCTP
specific characteristics with the help of the simulation will finally result in
solutions that lead to a better performance.
The deployment of SCTP will be another concern that can be improved
by introducing a specific Network Address Translation (NAT) for SCTP.Zugriff auf den Volltext ist gesperrt, neue Version unter DuEPublico-ID 35000
Das Stream Control Transmission Protocol (SCTP) wurde ursprünglich für
den Transport von Signalisierungsnachrichten über IP basierte Netze konzipiert.
Inzwischen hat es sich jedoch zu einem allgemeinen Transportprotokoll
entwickelt, das einzigartige Eigenschaften besitzt. Daher ist es
besonders für Anwendungen interessant, die von mehreren Netzwerkadressen
pro Verbindung (Multihoming), mehreren unabhängigen Nachrichtenströmen
oder einer der zahlreichen Protokollerweiterungen profitieren können. Mittlerweile
hat SCTP in die Betriebssystemkerne aller UNIX-Derivate und eines
Windows Prototyps Einzug gehalten, aber es gibt noch Mängel, deren Ursachen
es zu entdecken und zu korrigieren gilt.
In dieser Dissertation wird zunächst eine Reihe von Werkzeugen bereitgestellt,
um die Grundlage für weitere Untersuchungen zu schaffen. Ausgehend
von der Analyse und dem Vergleich von Implementierungen im Systemkern
verschiedener Betriebssysteme werden einige Aspekte des Protokolls
untersucht, die zu unerwünschtem Verhalten führen. Die Prinzipien der
Überlast- und Flusskontrolle wurden vom stream-orientierten Transmission
Control Protocol (TCP) übernommen und benutzen daher dieselben Mechanismen.
SCTP als nachrichtenorientiertes Protokoll benötigt jedoch eine
diesem Unterschied Rechnung tragende Implementierung der Algorithmen.
Die Analyse von SCTP-spezifischen Charakteristika mithilfe der Simulation
wird schließlich zu Lösungen führen und zu einer Verbesserung des Durchsatzes.
Ein weiteres Anliegen dieser Arbeit ist die Verbreitung von SCTP. Sie
kann durch die Einführung einer SCTP-spezifischen Methode zur Umsetzung
von Netzwerkadressen (Network Address Translation (NAT)) verbessert werden
Cross-layer RaCM design for vertically integrated wireless networks
Includes bibliographical references (p. 70-74).Wireless local and metropolitan area network (WLAN/WMAN) technologies, more specifically IEEE 802.11 (or wireless fidelity, WiFi) and IEEE 802.16 (or wireless interoperability for microwave access, WiMAX), are well-suited to enterprise networking since wireless offers the advantages of rapid deployment in places that are difficult to wire. However, these networking standards are relatively young with respect to their traditional mature high-speed low-latency fixed-line networking counterparts. It is more challenging for the network provider to supply the necessary quality of service (QoS) to support the variety of existing multimedia services over wireless technology. Wireless communication is also unreliable in nature, making the provisioning of agreed QoS even more challenging. Considering the advantages and disadvantages, wireless networks prove well-suited to connecting rural areas to the Internet or as a networking solution for areas that are difficult to wire. The focus of this study specifically pertains to IEEE 802.16 and the part it plays in an IEEE vertically integrated wireless Internet (WIN): IEEE 802.16 is a wireless broadband backhaul technology, capable of connecting local area networks (LANs), wireless or fixed-line, to the Internet via a high-speed fixed-line link
A blockchain-based trust management system for 5G network slicing enabled C-RAN
The mobility nature of the wireless networks and the time-sensitive tasks make it necessary for the system to transfer the messages with a minimum delay. Cloud Radio Access Network (C-RAN) reduces the latency problem. However, due to the trustlessness of 5G networks resulting from the heterogeneity nature of devices. In this article, for the edge devices, there is a need to maintain a trust level in the C-RAN node by checking the rates of devices that are allowed to share data among other devices. The SDN controller is built into a macro-cell that plays the role of a cluster head. The blockchain-based automatically authenticates the edge devices by assigning a unique identification that is shared by the cluster head with all C-RAN nodes connected to it. Simulation results demonstrate that, compared with the benchmark, the proposed approach significantly improves the processing time of blocks, the detection accuracy of malicious nodes, and transaction transmission delay
Enhancing Capacity and Network Performance of Client-Server Architectures Using Mobile IPv6 Host-Based Network Protocol
A huge number of studies have been done supporting seamless mobility networks and mobile technologies over the years The recent innovations in technology have unveiled another revolution from the static architectural approach to more dynamic and even mobile approaches for client-server networks Due to the special equipments and infrastructure needed to support network mobility management it is difficult to deploy such networks beyond the local network coverage without interruption of communications Therefore MIPv6 as developed by the Internet Engineering Task Force IETF and ancillary technologies were reviewed to provide clear insights on implementing MIPv6 in Client-Server architectures However MIPv6 technology presents weaknesses related to its critical handover latency which appears long for real-time applications such as Video Stream with potential loss of data packets during transmissio
Topology and congestion invariant in global internet-scale networks
PhDInfrastructures like telecommunication systems, power transmission
grids and the Internet are complex networks that are vulnerable to
catastrophic failure. A common mechanism behind this kind of failure
is avalanche-like breakdown of the network's components. If a
component fails due to overload, its load will be redistributed, causing
other components to overload and fail. This failure can propagate
throughout the entire network. From studies of catastrophic failures in
di erent technological networks, the consensus is that the occurrence
of a catastrophe is due to the interaction between the connectivity
and the dynamical behaviour of the networks' elements.
The research in this thesis focuses particularly on packet-oriented networks.
In these networks the tra c (dynamics) and the topology
(connectivity) are coupled by the routing mechanisms. The interactions
between the network's topology and its tra c are complex as
they depend on many parameters, e.g. Quality of Service, congestion
management (queuing), link bandwidth, link delay, and types of
tra c. It is not straightforward to predict whether a network will
fail catastrophically or not. Furthermore, even if considering a very
simpli ed version of packet networks, there are still fundamental questions
about catastrophic behaviour that have not been studied, such
as: will a network become unstable and fail catastrophically as its size
increases; do catastrophic networks have speci c connectivity properties?
One of the main di culties when studying these questions is that,
in general, we do not know in advance if a network is going to fail
catastrophically. In this thesis we study how to build catastrophic
5
networks. The motivation behind the research is that once we have
constructed networks that will fail catastrophically then we can study
its behaviour before the catastrophe occurs, for example the dynamical
behaviour of the nodes before an imminent catastrophe.
Our theoretical and algorithmic approach is based on the observation
that for many simple networks there is a topology-tra c invariant for
the onset of congestion. We have extended this approach to consider
cascading congestion. We have developed two methods to construct
catastrophes. The main results in this thesis are that there is a family
of catastrophic networks that have a scale invariant; hence at the
break point it is possible to predict the behaviour of large networks
by studying a much smaller network. The results also suggest that
if the tra c on a network increases exponentially, then there is a
maximum size that a network can have, after that the network will
always fail catastrophically.
To verify if catastrophic networks built using our algorithmic approach
can re
ect real situations, we evaluated the performance of a small
catastrophic network. By building the scenario using open source
network simulation software OMNet++, we were able to simulate a
router network using the Open Shortest Path First routing protocol
and carrying User Datagram Protocol tra c. Our results show that
this kind of networks can collapse as a cascade of failures. Furthermore,
recently the failure of Google Mail routers [1] con rms this kind
of catastrophic failure does occur in real situations
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