16 research outputs found
Multichannel optical access networks : design and resource management
At present there is a strong worldwide push towards bringing fiber closer to individual homes and businesses. The next evolutionary step is the cost-effective all-optical integration of fiber-based access and metro networks. STARGATE [1] is an all-optical access-metro architecture which does not rely on costly active devices, e.g., Optical Cross-Connects (OXCs) or Fixed Wavelength Converters (FWCs), and allow low-cost PON technologies to follow low-cost Ethernet technologies from EPON access into metro networks, resulting in significantly reduced cost and complexity. It makes use of an overlay island of transparency with optical bypassing capabilities. In this thesis we first propose Optical Network Unit (ONU) architectures, and discuss several technical challenges, which allow STARGATE EPONs (SG-EPONs) to evolve in a pay-as-you-grow manner while providing backward compatibility with legacy infrastructure and protecting previous investment. Second, and considering all the hardware constraints, we present the corresponding dynamic bandwidth allocation algorithm for effective resource management in these networks and investigate their performances (delay, throughput) through simulation experiments. We further investigate the problem of transmission grant scheduling in multichannel optical access networks using a scheduling theoretic approach. We show that the problem can be modeled as an Open Shop and we formulate the joint scheduling and wavelength assignment problem as a Mixed Integer Linear Program (MJLP) whose objective is to reduce the length of a scheduling period. Since the problem is known to be NP-hard, we introduce a Tabu Search based heuristic for solving the joint problem. Different other heuristics are also considered and their performances are compared with those of Tabu and MILP. Results indicate that by appropriately scheduling transmission grants and assigning wavelengths, substantial and consistent improvements may be obtained in the network performance. For example, Tabu shows a reduction of up to 29% in the schedule length with substantial reduction in channel idle gaps yielding to both higher channel utilization and lower queuing delays. Additionally, when the number of channels in the network is not small, the benefits of performing appropriate wavelength assignment, together with transmission scheduling, are observed and discussed. We further perform a packet-level simulation on the considered network to study the benefits of efficient grant scheduling; significant improvements are shown both in terms of system utilization and packet queuing delays
Optimization of multiple PON deployment costs and comparison between GPON, XGPON, NGPON2 and UDWDM PON
In this paper we propose an optimization framework for multiple deployment of PON in a wide region with very large number of users, with different bit rate demands, serviced by many central offices, as it may practically happen in a large city that plans a massive introduction of Fiber to the Home technologies using PON. We propose an algorithm called Optimal Topology Search (OTS), which is based on a set of heuristic approaches, capable of performing an optimal dimensioning of multiple PON deployments for a set of central offices (CO), including an optimal distribution of users among the CO. The set of heuristics integrated in OTS permit the efficient clustering of users for each CO, depending on their location and the bit rate demanded by them. It also permits the definition of optimal routes for optical cables and the allocation of branching devices. Taking into account hardware capacity restrictions and physical layer restrictions, we obtained solutions for different types of standardized PON technologies, like GPON, XGPON and NGPON2 as well as for future UDWDM-PON. We evaluate the optimal network deployment in a series of different minimum guaranteed bit rate demand scenarios, employing realistic maps of a large city in order to compare costs and portrait some reference points for deciding in which scenario a specific technology constitutes the best choice
Efficient Algorithms for Infrastructure Networks: Planning Issues and Economic Impact
Mei, R.D. van der [Promotor]Bhulai, S. [Copromotor
Integração do paradigma de cloud computing com a infraestrutura de rede do operador
Doutoramento em Engenharia InformáticaThe proliferation of Internet access allows that users have the possibility to use
services available directly through the Internet, which translates in a change of
the paradigm of using applications and in the way of communicating,
popularizing in this way the so-called cloud computing paradigm. Cloud
computing brings with it requirements at two different levels: at the cloud level,
usually relying in centralized data centers, where information technology and
network resources must be able to guarantee the demand of such services;
and at the access level, i.e., depending on the service being consumed,
different quality of service is required in the access network, which is a Network
Operator (NO) domain. In summary, there is an obvious network dependency.
However, the network has been playing a relatively minor role, mostly as a
provider of (best-effort) connectivity within the cloud and in the access network.
The work developed in this Thesis enables for the effective integration of cloud
and NO domains, allowing the required network support for cloud. We propose
a framework and a set of associated mechanisms for the integrated
management and control of cloud computing and NO domains to provide endto-
end services. Moreover, we elaborate a thorough study on the embedding of
virtual resources in this integrated environment. The study focuses on
maximizing the host of virtual resources on the physical infrastructure through
optimal embedding strategies (considering the initial allocation of resources as
well as adaptations through time), while at the same time minimizing the costs
associated to energy consumption, in single and multiple domains.
Furthermore, we explore how the NO can take advantage of the integrated
environment to host traditional network functions. In this sense, we study how
virtual network Service Functions (SFs) should be modelled and managed in a
cloud environment and enhance the framework accordingly.
A thorough evaluation of the proposed solutions was performed in the scope of
this Thesis, assessing their benefits. We implemented proof of concepts to
prove the added value, feasibility and easy deployment characteristics of the
proposed framework. Furthermore, the embedding strategies evaluation has
been performed through simulation and Integer Linear Programming (ILP)
solving tools, and it showed that it is possible to reduce the physical
infrastructure energy consumption without jeopardizing the virtual resources
acceptance. This fact can be further increased by allowing virtual resource
adaptation through time. However, one should have in mind the costs
associated to adaptation processes. The costs can be minimized, but the virtual
resource acceptance can be also reduced. This tradeoff has also been subject
of the work in this Thesis.A proliferação do acesso à Internet permite aos utilizadores usar serviços
disponibilizados diretamente através da Internet, o que se traduz numa
mudança de paradigma na forma de usar aplicações e na forma de comunicar,
popularizando desta forma o conceito denominado de cloud computing. Cloud
computing traz consigo requisitos a dois níveis: ao nível da própria cloud,
geralmente dependente de centros de dados centralizados, onde as
tecnologias de informação e recursos de rede têm que ser capazes de garantir
as exigências destes serviços; e ao nível do acesso, ou seja, dependendo do
serviço que esteja a ser consumido, são necessários diferentes níveis de
qualidade de serviço na rede de acesso, um domínio do operador de rede. Em
síntese, existe uma clara dependência da cloud na rede. No entanto, o papel
que a rede tem vindo a desempenhar neste âmbito é reduzido, sendo
principalmente um fornecedor de conectividade (best-effort) tanto no dominio
da cloud como no da rede de acesso.
O trabalho desenvolvido nesta Tese permite uma integração efetiva dos
domínios de cloud e operador de rede, dando assim à cloud o efetivo suporte
da rede. Para tal, apresentamos uma plataforma e um conjunto de
mecanismos associados para gestão e controlo integrado de domínios cloud
computing e operador de rede por forma a fornecer serviços fim-a-fim. Além
disso, elaboramos um estudo aprofundado sobre o mapeamento de recursos
virtuais neste ambiente integrado. O estudo centra-se na maximização da
incorporação de recursos virtuais na infraestrutura física por meio de
estratégias de mapeamento ótimas (considerando a alocação inicial de
recursos, bem como adaptações ao longo do tempo), enquanto que se
minimizam os custos associados ao consumo de energia. Este estudo é feito
para cenários de apenas um domínio e para cenários com múltiplos domínios.
Além disso, exploramos como o operador de rede pode aproveitar o referido
ambiente integrado para suportar funções de rede tradicionais. Neste sentido,
estudamos como as funções de rede virtualizadas devem ser modeladas e
geridas num ambiente cloud e estendemos a plataforma de acordo com este
conceito.
No âmbito desta Tese foi feita uma avaliação extensa das soluções propostas,
avaliando os seus benefícios. Implementámos provas de conceito por forma a
demonstrar as mais-valias, viabilidade e fácil implantação das soluções
propostas. Além disso, a avaliação das estratégias de mapeamento foi
realizada através de ferramentas de simulação e de programação linear inteira,
mostrando que é possível reduzir o consumo de energia da infraestrutura
física, sem comprometer a aceitação de recursos virtuais. Este aspeto pode
ser melhorado através da adaptação de recursos virtuais ao longo do tempo.
No entanto, deve-se ter em mente os custos associados aos processos de
adaptação. Os custos podem ser minimizados, mas isso implica uma redução
na aceitação de recursos virtuais. Esta compensação foi também um tema
abordado nesta Tese
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A software-defined survivability approach for wireless sensor networks in future internet of the things
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe Internet of the Things (IoT) is evolving rapidly, and its significant impacts
are expected to affect many application domains. Challenges in areas that humans
have been striving to understand, measure, or predict—such as wildlife, healthcare,
or environmental hazards—are likely to be addressed by the time IoT emerges.
The underlying elements of IoT are wireless sensor networks (WSNs),
which consist of a large number of sensor nodes. In the IoT sphere, sensor nodes
represent tangible objects—Things—that monitor changes, collect information,
and eventually send it through the Internet to a recipient party. Inherently, however,
a wireless sensor node relies on limited computational resources with a limited
power source. These undesirable qualities result in a low level of dependability.
This research explores the viability of applying the unfolding network programmability
concepts to overcome survivability obstacles in WSNs and the IoT. In particular,
it examines the viability of software-defined networking (SDN) in network
lifetime maximisation, failure detection, and failure recovery problems in WSNs.
Software-defined networking is a new network programmability concept
that separates the traditionally-tied control and data planes. It offloads the route
computations and management from network devices to a logically centralised
controller. This separation directly leads to better allocation of computational
resources for the network nodes and allows endless orchestration possibilities for
the controller. This thesis proposes an SDN-based solution to increase the survivability
and resilience of WSN environments. Following an approach that conforms
with the centralised nature of SDN environments and considers the limited resources
of the WSN.
A routing algorithm based on A-star was developed for WSNs, then deployed
within an SDN environment to maximise the network lifetime. Apart from finding the path with the lowest energy burden, the algorithm offloads most of
the control traffic from sensor nodes to the controller. This algorithm resulted
in improved resource utilisation among the nodes due to plane decoupling. Additionally,
it increased the lifetime of the network by 22.6% compared to the widely
explored LEACH protocol.
This thesis also investigates different failure detection and recovery practices
in the SDN architecture. The simulation results show that adopting bidirectional
forwarding detection (BFD) with the asynchronous echo mode for WSN
in an SDN environment reduces control traffic for failure detection to between
27% and 48%. The thesis also evaluates the performance of multiple recovery approaches
when adopting the premises of SDN. The simulation results indicate that
path protection, using group tables from the OpenFlow protocol, has a recovery
time up to eight times shorter than the restoration time. The results of the study
reveal that using protection as a failure recovery technique significantly reduces
control traffic overhead
Enabling Technology in Optical Fiber Communications: From Device, System to Networking
This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking