320 research outputs found
Cost-effective Information and Communication Technology (ICT) infrastructure for Tanziania
The research conducted an Information and Communication Technology (ICT) field
survey, the results revealed that Tanzania is still lagging behind in the ICT sector due to
the lack of an internationally connected terrestrial ICT infrastructure; Internet connectivity
to the rest of the world is via expensive satellite links, thus leaving the majority of the
population unable to access the Internet services due to its high cost. Therefore, an ICT
backbone infrastructure is designed that exploits optical DWDM network technology,
which un-locks bandwidth bottlenecks and provides higher capacity which will provide
ICT services such as Internet, voice, videos and other multimedia interactions at an
affordable cost to the majority of the people who live in the urban and rural areas of
Tanzania. The research analyses and compares the performance, and system impairments, in a DWDM system at data transmission rates of 2.5 Gb/s and 10 Gb/s per wavelength channel. The simulation results show that a data transmission rate of 2.5 Gb/s can be successfully transmitted over a greater distance than 10 Gb/s with minimum system impairments. Also operating at the lower data rate delivers a good system performance for the required ICT services. A forty-channel DWDM system will provide a bandwidth of 100 Gb/s.
A cost analysis demonstrates the economic worth of incorporating existing optical fibre
installations into an optical DWDM network for the creation of an affordable ICT
backbone infrastructure; this approach is compared with building a completely new optical
fibre DWDM network or a SONET/SDH network. The results show that the ICT backbone
infrastructure built with existing SSMF DWDM network technology is a good investment,
in terms of profitability, even if the Internet charges are reduced to half current rates. The
case for building a completely new optical fibre DWDM network or a SONET/SDH
network is difficult to justify using current financial data
Optimization in Telecommunication Networks
Network design and network synthesis have been the classical optimization problems intelecommunication for a long time. In the recent past, there have been many technologicaldevelopments such as digitization of information, optical networks, internet, and wirelessnetworks. These developments have led to a series of new optimization problems. Thismanuscript gives an overview of the developments in solving both classical and moderntelecom optimization problems.We start with a short historical overview of the technological developments. Then,the classical (still actual) network design and synthesis problems are described with anemphasis on the latest developments on modelling and solving them. Classical results suchas Mengerâs disjoint paths theorem, and Ford-Fulkersonâs max-flow-min-cut theorem, butalso Gomory-Hu trees and the Okamura-Seymour cut-condition, will be related to themodels described. Finally, we describe recent optimization problems such as routing andwavelength assignment, and grooming in optical networks.operations research and management science;
Investigation of the tolerance of wavelength-routed optical networks to traffic load variations.
This thesis focuses on the performance of circuit-switched wavelength-routed optical network with unpredictable traffic pattern variations. This characteristic of optical networks is termed traffic forecast tolerance. First, the increasing volume and heterogeneous nature of data and voice traffic is discussed. The challenges in designing robust optical networks to handle unpredictable traffic statistics are described. Other work relating to the same research issues are discussed. A general methodology to quantify the traffic forecast tolerance of optical networks is presented. A traffic model is proposed to simulate dynamic, non-uniform loads, and used to test wavelength-routed optical networks considering numerous network topologies. The number of wavelengths required and the effect of the routing and wavelength allocation algorithm are investigated. A new method of quantifying the network tolerance is proposed, based on the calculation of the increase in the standard deviation of the blocking probabilities with increasing traffic load non-uniformity. The performance of different networks are calculated and compared. The relationship between physical features of the network topology and traffic forecast tolerance is investigated. A large number of randomly connected networks with different sizes were assessed. It is shown that the average lightpath length and the number of wavelengths required for full interconnection of the nodes in static operation both exhibit a strong correlation with the network tolerance, regardless of the degree of load non-uniformity. Finally, the impact of wavelength conversion on network tolerance is investigated. Wavelength conversion significantly increases the robustness of optical networks to unpredictable traffic variations. In particular, two sparse wavelength conversion schemes are compared and discussed: distributed wavelength conversion and localized wavelength conversion. It is found that the distributed wavelength conversion scheme outperforms localized wavelength conversion scheme, both with uniform loading and in terms of the network tolerance. The results described in this thesis can be used for the analysis and design of reliable WDM optical networks that are robust to future traffic demand variations
Towards a cloud enabler : from an optical network resource provisioning system to a generalized architecture for dynamic infrastructure services provisioning
This work was developed during a period where most of the optical management and provisioning system where manual and proprietary. This work contributed to the evolution of the state of the art of optical networks with new architectures and advanced virtual infrastructure services. The evolution of optical networks, and internet globally, have been very promising during the last decade. The impact of mobile technology, grid, cloud computing, HDTV, augmented reality and big data, among many others, have driven the evolution of optical networks towards current service technologies, mostly based on SDN (Software Defined Networking) architectures and NFV(Network Functions Virtualisation). Moreover, the convergence of IP/Optical networks and IT services, and the evolution of the internet and optical infrastructures, have generated novel service orchestrators and open source frameworks. In fact, technology has evolved that fast that none could foresee how important Internet is for our current lives. Said in other words, technology was forced to evolve in a way that network architectures became much more transparent, dynamic and flexible to the end users (applications, user interfaces or simple APIs).
This Thesis exposes the work done on defining new architectures for Service Oriented Networks and the contribution to the state of the art. The research work is divided into three topics. It describes the evolution from a Network Resource Provisioning System to an advanced Service Plane, and ends with a new architecture that virtualized the optical infrastructure in order to provide coordinated, on-demand and dynamic services between the application and the network infrastructure layer, becoming an enabler for the new generation of cloud network infrastructures.
The work done on defining a Network Resource Provisioning System established the first bases for future work on network infrastructure virtualization. The UCLP (User Light Path Provisioning) technology was the first attempt for Customer Empowered Networks and Articulated Private Networks. It empowered the users and brought virtualization and partitioning functionalities into the optical data plane, with new interfaces for dynamic service provisioning. The work done within the development of a new Service Plane allowed the provisioning of on-demand connectivity services from the application, and in a multi-domain and multi-technology scenario based on a virtual network infrastructure composed of resources from different infrastructure providers. This Service Plane facilitated the deployment of applications consuming large amounts of data under deterministic conditions, so allowing the networks behave as a Grid-class resource. It became the first on-demand provisioning system that at lower levels allowed the creation of one virtual domain composed from resources of different providers.
The last research topic presents an architecture that consolidated the work done in virtualisation while enhancing the capabilities to upper layers, so fully integrating the optical network infrastructure into the cloud environment, and so providing an architecture that enabled cloud services by integrating the request of optical network and IT infrastructure services together at the same level. It set up a new trend into the research community and evolved towards the technology we use today based on SDN and NFV.
Summing up, the work presented is focused on the provisioning of virtual infrastructures from the architectural point of view of optical networks and IT infrastructures, together with the design and definition of novel service layers. It means, architectures that enabled the creation of virtual infrastructures composed of optical networks and IT resources, isolated and provisioned on-demand and in advance with infrastructure re-planning functionalities, and a new set of interfaces to open up those services to applications or third parties.Aquesta tesi es va desenvolupar durant un perĂode on la majoria de sistemes de gestiĂł de xarxa òptica eren manuals i basats en sistemes propietaris. En aquest sentit, la feina presentada va contribuir a l'evoluciĂł de l'estat de l'art de les xarxes òptiques tant a nivell dâarquitectures com de provisiĂł dâinfraestructures virtuals. L'evoluciĂł de les xarxes òptiques, i d'Internet a nivell mundial, han estat molt prometedores durant l'Ăşltima dècada. L'impacte de la tecnologia mòbil, la computaciĂł al nĂşvol, la televisiĂł d'alta definiciĂł, la realitat augmentada i el big data, entre molts altres, han impulsat l'evoluciĂł cap a xarxes dâaltes prestacions amb nous serveis basats en SDN (Software Defined Networking) i NFV (Funcions de xarxa La virtualitzaciĂł). D'altra banda, la convergència de xarxes òptiques i els serveis IT, junt amb l'evoluciĂł d'Internet i de les infraestructures òptiques, han generat nous orquestradors de serveis i frameworks basats en codi obert. La tecnologia ha evolucionat a una velocitat on ningĂş podria haver predit la importĂ ncia que Internet estĂ tenint en el nostre dia a dia. Dit en altres paraules, la tecnologia es va veure obligada a evolucionar d'una manera on les arquitectures de xarxa es fessin mĂŠs transparent, dinĂ miques i flexibles vers als usuaris finals (aplicacions, interfĂcies d'usuari o APIs simples). Aquesta Tesi presenta noves arquitectures de xarxa òptica orientades a serveis. El treball de recerca es divideix en tres temes. Es presenta un sistema de virtualitzaciĂł i aprovisionament de recursos de xarxa i la seva evoluciĂł a un pla de servei avançat, per acabar presentant el disseny dâuna nova arquitectura capaç de virtualitzar la infraestructura òptica i IT i proporcionar serveis de forma coordinada, i sota demanda, entre l'aplicaciĂł i la capa d'infraestructura de xarxa òptica. Tot esdevenint un facilitador per a la nova generaciĂł d'infraestructures de xarxa en el nĂşvol. El treball realitzat en la definiciĂł del sistema de virtualitzaciĂł de recursos va establir les primeres bases sobre la virtualitzaciĂł de la infraestructura de xarxa òptica en el marc de les âCustomer Empowered Networksâ i âArticulated Private Networksâ. Amb lâobjectiu de virtualitzar el pla de dades òptic, i oferir noves interfĂcies per a la provisiĂł de serveis dinĂ mics de xarxa. En quant al pla de serveis presentat, aquest va facilitat la provisiĂł de serveis de connectivitat sota demanda per part de l'aplicaciĂł, tant en entorns multi-domini, com en entorns amb mĂşltiples tecnologies. Aquest pla de servei, anomenat Harmony, va facilitar el desplegament de noves aplicacions que consumien grans quantitats de dades en condicions deterministes. En aquest sentit, va permetre que les xarxes es comportessin com un recurs Grid, i per tant, va esdevenir el primer sistema d'aprovisionament sota demanda que permetia la creaciĂł de dominis virtuals de xarxa composts a partir de recursos de diferents proveĂŻdors. Finalment, es presenta lâevoluciĂł dâun pla de servei cap una arquitectura global que consolida el treball realitzat a nivell de convergència dâinfraestructures (òptica + IT) i millora les capacitats de les capes superiors. Aquesta arquitectura va facilitar la plena integraciĂł de la infraestructura de xarxa òptica a l'entorn del nĂşvol. En aquest sentit, aquest resultats van evolucionar cap a les tendències actuals de SDN i NFV. En resum, el treball presentat es centra en la provisiĂł d'infraestructures virtuals des del punt de vista dâarquitectures de xarxa òptiques i les infraestructures IT, juntament amb el disseny i definiciĂł de nous serveis de xarxa avançats, tal i com ho va ser el servei de re-planificaciĂł dinĂ micaPostprint (published version
Traffic grooming and wavelength conversion in optical networks
Wavelength Division Multiplexing (WDM) using wavelength routing has emerged as the dominant technology for use in wide area and metropolitan area networks. Traffic demands in networks today are characterized by dynamic, heterogeneous flows. While each wavelength has transmission capacity at gigabit per second rates, users require connections at rates that are lower than the full wavelength capacity. In this thesis, we explore network design and operation methodologies to improve the network utilization and blocking performance of wavelength routing networks which employ a layered architecture with electronic and optical switching. First we provide an introduction to first generation SONET/SDH networks and wavelength routing networks, which employ optical crossconnects. We explain the need and role of wavelength conversion in optical networks and present an algorithm to optimally place wavelength conversion devices at the network nodes so as to optimize blocking performance. Our algorithm offers significant savings in computation time when compared to the exhaustive method.;To make the network viable and cost-effective, it must be able to offer sub-wavelength services and be able to pack these services efficiently onto wavelengths. The act of multiplexing, demultiplexing and switching of sub-wavelength services onto wavelengths is defined as traffic grooming. Constrained grooming networks perform grooming only at the network edge. Sparse grooming networks perform grooming at the network edge and the core. We study and compare the effect of traffic grooming on blocking performance in such networks through simulations and analyses. We also study the issue of capacity fairness in such networks and develop a connection admission control (CAC) algorithm to improve the fairness among connections with different capacities. We finally address the issues involved in dynamic routing and wavelength assignment in survivable WDM grooming networks. We develop two schemes for grooming primary and backup traffic streams onto wavelengths: Mixed Primary-Backup Grooming Policy (MGP) and Segregated Primary-Backup Grooming Policy (SGP). MGP is useful in topologies such as ring, characterized by low connectivity and high load correlation and SGP is useful in topologies, such as mesh-torus, with good connectivity and a significant amount of traffic switching and mixing at the nodes
Design Related Investigations for Media Access Control Protocol Service Schemes in Wavelength Division Multiplexed All Optical Networks
All-optical networks (AON) are emerging through the technological
advancement of various optical components, and promise to provide almost unlimited
bandwidth. To realise true network utilisation, software solutions are required. An active
area of research is media access control (MAC) protocol. This protocol should address
the multiple channels by wavelength division mutiplexing (WDM) and bandwidth
management. Token-passing (TP) is one such protocol, and is adopted due to its
simplicity and collisionless nature. Previously, this protocol has been analysed for a
single traffic type. However, such a study may not substantiate the protocol's acceptance
in the AON design. As multiple traffic types hog the network through the introduction
multimedia services and Internet, the MAC protocol should support this traffic. Four
different priority schemes are proposed for TP protocol extension, and classified as static and dynamic schemes. Priority assignments are a priori in static scheme, whereas in the
other scheme, priority reassignments are carried out dynamically. Three different
versions of dynamic schemes are proposed. The schemes are investigated for
performance through analytical modelling and simulations. The semi-Markov process
(SMP) modelling approach is extended for the analyses of these cases. In this technique,
the behaviour of a typical access node needs to be considered. The analytical results are
compared with the simulation results. The deviations of the results are within the
acceptable limits, indicating the applicability ofthe model in all-optical environment.
It is seen that the static scheme offers higher priority traffic better delay and
packet loss performance. Thus, this scheme can be used beneficially in hard real-time
systems, where knowledge of priority is a priori. The dynamic priority scheme-l is more
suitable for the environments where the lower priority traffic is near real-time traffic and
loss sensitive too. For such a scheme, a larger buffer with smaller threshold limits
resulted in improved performance. The dynamic scheme-2 and 3 can be employed to
offer equal treatment for the different traffic types, and more beneficial in future AONs.
These schemes are also compared in their performance to offer constant QoS level. New
parameters to facilitate the comparison are proposed. It is observed that the dynamic
scheme-l outperforms the other schemes, and these QoS parameters can be used for
such QoS analysis. It is concluded that the research can benefit the design of the
protocol and its service schemes needed in AON system and its applications
Open Layered Networks: the Growing Importance of Market Coordination
Based upon the Internet perspective, this paper will attempt to clarify and revise
several ideas about the separation between infrastructure facilities and service
offerings in digital communications networks. The key notions that we will focus on in
this paper are: i) the bearer service as a technology-independent interface which
exports blind network functionality to applications development; ii) the organizational
consequences associated with the emergence of a sustainable market of bearer service:
a clear movement at the level of industrial structure from traditional hierarchies to
more market coordination
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