22 research outputs found
Distributed resource discovery: architectures and applications in mobile networks
As the amount of digital information and services increases, it becomes increasingly important to be able to locate the desired content. The purpose of a resource discovery system is to allow available resources (information or services) to be located using a user-defined search criterion. This work studies distributed resource discovery systems that guarantee all existing resources to be found and allow a wide range of complex queries. Our goal is to allocate the load uniformly between the participating nodes, or alternatively to concentrate the load in the nodes with the highest available capacity.
The first part of the work examines the performance of various existing unstructured architectures and proposes new architectures that provide features especially valuable in mobile networks. To reduce the network traffic, we use indexing, which is particularly useful in scenarios, where searches are frequent compared to resource modifications. The ratio between the search and update frequencies determines the optimal level of indexing. Based on this observation, we develop an architecture that adjusts itself to changing network conditions and search behavior while maintaining optimal indexing. We also propose an architecture based on large-scale indexing that we later apply to resource sharing within a user group. Furthermore, we propose an architecture that relieves the topology constraints of the Parallel Index Clustering architecture. The performance of the architectures is evaluated using simulation.
In the second part of the work we apply the architectures to two types of mobile networks: cellular networks and ad hoc networks. In the cellular network, we first consider scenarios where multiple commercial operators provide a resource sharing service, and then a scenario where the users share resources without operator support. We evaluate the feasibility of the mobile peer-to-peer concept using user opinion surveys and technical performance studies. Based on user input we develop access control and group management algorithms for peer-to-peer networks. The technical evaluation is performed using prototype implementations. In particular, we examine whether the Session Initiation Protocol can be used for signaling in peer-to-peer networks. Finally, we study resource discovery in an ad hoc network. We observe that in an ad hoc network consisting of consumer devices, the capacity and mobility among nodes vary widely. We utilize this property in order to allocate the load to the high-capacity nodes, which serve lower-capacity nodes. We propose two methods for constructing a virtual backbone connecting the nodes
Provision, discovery and development of ubiquitous services and applications
Ph.DDOCTOR OF PHILOSOPH
Resource discovery for distributed computing systems: A comprehensive survey
Large-scale distributed computing environments provide a vast amount of heterogeneous computing resources from different sources for resource sharing and distributed computing. Discovering appropriate resources in such environments is a challenge which involves several different subjects. In this paper, we provide an investigation on the current state of resource discovery protocols, mechanisms, and platforms for large-scale distributed environments, focusing on the design aspects. We classify all related aspects, general steps, and requirements to construct a novel resource discovery solution in three categories consisting of structures, methods, and issues. Accordingly, we review the literature, analyzing various aspects for each category
Redes em malha sem fios baseadas em contexto
Doutoramento em Engenharia ElectrotécnicaIn the modern society, new devices, applications and technologies, with sophisticated
capabilities, are converging in the same network infrastructure.
Users are also increasingly demanding in personal preferences and expectations,
desiring Internet connectivity anytime and everywhere. These aspects
have triggered many research efforts, since the current Internet is reaching
a breaking point trying to provide enough flexibility for users and profits for
operators, while dealing with the complex requirements raised by the recent
evolution.
Fully aligned with the future Internet research, many solutions have been
proposed to enhance the current Internet-based architectures and protocols,
in order to become context-aware, that is, to be dynamically adapted to
the change of the information characterizing any network entity. In this
sense, the presented Thesis proposes a new architecture that allows to create
several networks with different characteristics according to their context, on
the top of a single Wireless Mesh Network (WMN), which infrastructure
and protocols are very flexible and self-adaptable.
More specifically, this Thesis models the context of users, which can span
from their security, cost and mobility preferences, devicesâ capabilities or
servicesâ quality requirements, in order to turn a WMN into a set of logical
networks. Each logical network is configured to meet a set of user context
needs (for instance, support of high mobility and low security). To
implement this user-centric architecture, this Thesis uses the network virtualization,
which has often been advocated as a mean to deploy independent
network architectures and services towards the future Internet, while allowing
a dynamic resource management. This way, network virtualization can
allow a flexible and programmable configuration of a WMN, in order to be
shared by multiple logical networks (or virtual networks - VNs). Moreover,
the high level of isolation introduced by network virtualization can be used
to differentiate the protocols and mechanisms of each context-aware VN.
This architecture raises several challenges to control and manage the VNs
on-demand, in response to user and WMN dynamics. In this context, we
target the mechanisms to: (i) discover and select the VN to assign to an
user; (ii) create, adapt and remove the VN topologies and routes. We
also explore how the rate of variation of the user context requirements can
be considered to improve the performance and reduce the complexity of
the VN control and management. Finally, due to the scalability limitations
of centralized control solutions, we propose a mechanism to distribute the
control functionalities along the architectural entities, which can cooperate
to control and manage the VNs in a distributed way.Na sociedade actual, novos dispositivos, aplicaçÔes e tecnologias, com capacidades
sofisticadas, estĂŁo a convergir na mesma infra-estrutura de rede.
Os utilizadores sĂŁo tambĂ©m cada vez mais exigentes nas suas preferĂȘncias e
expectativas pessoais, desejando conetividade `a Internet em qualquer hora
e lugar. Estes aspectos tĂȘm desencadeado muitos esforços de investigação,
dado que a Internet atual estĂĄ a atingir um ponto de rutura ao tentar promover
flexibilidade para os utilizadores e lucros para os operadores, enquanto
lida com as exigĂȘncias complexas associadas `a recente evolução.
Em sintonia com a linha de investigação para a Internet do futuro, muitas
soluçÔes tĂȘm sido propostas para melhorar as arquiteturas e protocolos da
Internet atual, de forma a tornĂĄ-los sensĂveis ao contexto, isto Ă©, adaptĂĄ-los
dinamicamente `a alteração da informação que caracteriza qualquer entidade
de rede. Neste sentido, a presente Tese propÔe uma nova arquitetura que
permite criar vĂĄrias redes com diferentes caracterĂsticas de acordo com o
contexto das mesmas, sobre uma Ășnica rede em malha sem fios (WMN),
cuja infra-estructura e protocolos sĂŁo muito flexĂveis e auto-adaptĂĄveis.
Mais especificamente, esta Tese modela o contexto dos utilizadores, que
pode abranger as suas preferĂȘncias de segurança, custo e mobilidade, capacidades
dos seus dispositivos ou requisitos de qualidade dos seus serviços,
de forma a transformar uma WMN num conjunto de redes lĂłgicas. Cada
rede lĂłgica ÂŽe configurada para satisfazer um conjunto de necessidades de
contexto do utilizador (como exemplo, suporte de mobilidade elevada e
de baixa seguranžca). Para implementar esta arquitetura centrada no utilizador,
esta Tese utiliza a virtualização de redes, que tem muitas vezes
sido defendida como um meio para implementar arquiteturas e serviços de
rede de uma forma independente, enquanto permite uma gestĂŁo dinĂąmica
dos recursos. Desta forma, a virtualização de redes pode permitir uma
configuração flexĂvel e programĂĄvel de uma WMN, a fim de ser partilhada
por vårias redes lógicas (ou redes virtuais - VNs). Além disso, o grau de
isolamento introduzido pela virtualização de redes pode ser utilizado para
diferenciar os protocolos e mecanismos de cada VN baseada em contexto.
Esta arquitetura levanta vĂĄrios desafios para controlar e gerir as VNs em
tempo real, e em resposta `a dinĂąmica dos utilizadores e da WMN. Neste
contexto, abordamos os mecanismos para: (i) descobrir e selecionar a VN
a atribuir a um utilizador; (ii) criar, adaptar e remover as topologias e
rotas das VNs. Também exploramos a possibilidade de considerar a taxa
de variação dos requisitos de contexto dos utilizadores de forma a melhorar
o desempenho e reduzir a complexidade do controlo e gestĂŁo das VNs.
Finalmente, devido Žas limitaçÔes de escalabilidade das soluçÔes de controlo
centralizadas, propomos um mecanismo para distribuir as funcionalidades
de controlo ao longo das entidades da arquitectura, que podem cooperar
para controlar e gerir as VNs de uma forma distribuĂda
A semantic approach for scalable and self-organized context-aware systems
Ph.DDOCTOR OF PHILOSOPH
A framework for the dynamic management of Peer-to-Peer overlays
Peer-to-Peer (P2P) applications have been associated with inefficient operation, interference with other network services and large operational costs for network providers. This thesis presents a framework which can help ISPs address these issues by means of intelligent management of peer behaviour. The proposed approach involves limited control of P2P overlays without interfering with the fundamental characteristics of peer autonomy and decentralised operation.
At the core of the management framework lays the Active Virtual Peer (AVP). Essentially intelligent peers operated by the network providers, the AVPs interact with the overlay from within, minimising redundant or inefficient traffic, enhancing overlay stability and facilitating the efficient and balanced use of available peer and network resources. They offer an âinsiderâsâ view of the overlay and permit the management of P2P functions in a compatible and non-intrusive manner. AVPs can support multiple P2P protocols and coordinate to perform functions collectively.
To account for the multi-faceted nature of P2P applications and allow the incorporation of modern techniques and protocols as they appear, the framework is based on a modular architecture. Core modules for overlay control and transit traffic minimisation are presented. Towards the latter, a number of suitable P2P content caching strategies are proposed.
Using a purpose-built P2P network simulator and small-scale experiments, it is demonstrated that the introduction of AVPs inside the network can significantly reduce inter-AS traffic, minimise costly multi-hop flows, increase overlay stability and load-balancing and offer improved peer transfer performance
DeMMon Decentralized Management and Monitoring Framework
The centralized model proposed by the Cloud computing paradigm mismatches the decentralized
nature of mobile and IoT applications, given the fact that most of the data
production and consumption is performed by end-user devices outside of the Data Center
(DC). As the number of these devices grows, and given the need to transport data to and
from DCs for computation, application providers incur additional infrastructure costs,
and end-users incur delays when performing operations.
These reasons have led us into a post-cloud era, where a new computing paradigm
arose: Edge Computing. Edge Computing takes into account the broad spectrum of
devices residing outside of the DC, closer to the clients, as potential targets for computations,
potentially reducing infrastructure costs, improving the quality of service (QoS)
for end-users and allowing new interaction paradigms between users and applications.
Managing and monitoring the execution of these devices raises new challenges previously
unaddressed by Cloud computing, given the scale of these systems and the devicesâ
(potentially) unreliable data connections and heterogenous computational power. The
study of the state-of-the-art has revealed that existing resource monitoring and management
solutions require manual configuration and have centralized components, which
we believe do not scale for larger-scale systems.
In this work, we address these limitations by presenting a novel Decentralized Management
and Monitoring (âDeMMonâ) system, targeted for edge settings. DeMMon provides
primitives to ease the development of tools that manage computational resources
that support edge-enabled applications, decomposed in components, through decentralized
actions, taking advantage of partial knowledge of the system. Our solution was
evaluated to amount to its benefits regarding information dissemination and monitoring
capabilities across a set of realistic emulated scenarios of up to 750 nodes with variable
failure rates. The results show the validity of our approach and that it can outperform
state-of-the-art solutions regarding scalability and reliabilityO modelo centralizado de computação utilizado no paradigma da Computação na Nuvem
apresenta limitaçÔes no contexto de aplicaçÔes no domĂnio da Internet das Coisas
e aplicaçÔes móveis. Neste tipo de aplicaçÔes, os dados são produzidos e consumidos
maioritariamente por dispositivos que se encontram na periferia da rede. Desta forma,
transportar estes dados de e para os centros de dados impÔe uma carga excessiva nas
infraestruturas de rede que ligam os dispositivos aos centros de dados, aumentando a
latĂȘncia de respostas e diminuindo a qualidade de serviço para os utilizadores.
Para combater estas limitaçÔes, surgiu o paradigma da Computação na Periferia, este
paradigma propÔe a execução de computaçÔes, e potencialmente armazenamento de
dados, em dispositivos fora dos centros de dados, mais perto dos clientes, reduzindo
custos e criando um novo leque de possibilidades para efetuar computaçÔes distribuĂdas
mais prĂłximas dos dispositivos que produzem e consomem os dados.
Contudo, gerir e supervisionar a execução desses dispositivos levanta obståculos não
equacionados pela Computação na Nuvem, como a escala destes sistemas, ou a variabilidade
na conectividade e na capacidade de computação dos dispositivos que os compÔem.
O estudo da literatura revela que ferramentas populares para gerir e supervisionar aplicaçÔes
e dispositivos possuem limitaçÔes para a sua escalabilidade, como por exemplo,
pontos de falha centralizados, ou requerem a configuração manual de cada dispositivo.
Nesta dissertação, propÔem-se uma nova solução de monitorização e disseminação
de informação descentralizada. Esta solução oferece operaçÔes que permitem recolher
informação sobre o estado do sistema, de modo a ser utilizada por soluçÔes (também
descentralizadas) que gerem aplicaçÔes especializadas para executar na periferia da rede.
A nossa solução foi avaliada em redes emuladas de vårias dimensÔes com um måximo
de 750 nós, no contexto de disseminação e de monitorização de informação. Os nossos
resultados mostram que o nosso sistema consegue ser mais robusto ao mesmo tempo que
Ă© mais escalĂĄvel quando comparado com o estado da arte
Efficient Passive Clustering and Gateways selection MANETs
Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets
Descoberta de recursos para sistemas de escala arbitrarias
Doutoramento em InformĂĄticaTecnologias de Computação DistribuĂda em larga escala tais como Cloud,
Grid, Cluster e Supercomputadores HPC estĂŁo a evoluir juntamente com a
emergĂȘncia revolucionĂĄria de modelos de mĂșltiplos nĂșcleos (por exemplo:
GPU, CPUs num Ășnico die, Supercomputadores em single die, Supercomputadores
em chip, etc) e avanços significativos em redes e soluçÔes de
interligação. No futuro, nĂłs de computação com milhares de nĂșcleos podem
ser ligados entre si para formar uma Ășnica unidade de computação
transparente que esconde das aplicaçÔes a complexidade e a natureza distribuĂda desses sistemas com mĂșltiplos nĂșcleos. A fim de beneficiar de forma
eficiente de todos os potenciais recursos nesses ambientes de computação
em grande escala com mĂșltiplos nĂșcleos ativos, a descoberta de recursos Ă© um elemento crucial para explorar ao mĂĄximo as capacidade de todos
os recursos heterogĂ©neos distribuĂdos, atravĂ©s do reconhecimento preciso e
localização desses recursos no sistema. A descoberta eficiente e escalåvel
de recursos ÂŽe um desafio para tais sistemas futuros, onde os recursos e as
infira-estruturas de computação e comunicação subjacentes são altamente
dinùmicas, hierarquizadas e heterogéneas. Nesta tese, investigamos o problema
da descoberta de recursos no que diz respeito aos requisitos gerais da
escalabilidade arbitrĂĄria de ambientes de computação futuros com mĂșltiplos
nĂșcleos ativos. A principal contribuição desta tese ÂŽe a proposta de uma
entidade de descoberta de recursos adaptativa hĂbrida (Hybrid Adaptive
Resource Discovery - HARD), uma abordagem de descoberta de recursos eficiente
e altamente escalĂĄvel, construĂda sobre uma sobreposição hierĂĄrquica
virtual baseada na auto-organizaçãoo e auto-adaptação de recursos de processamento
no sistema, onde os recursos computacionais sĂŁo organizados
em hierarquias distribuĂdas de acordo com uma proposta de modelo de
descriçãoo de recursos multi-camadas hierårquicas. Operacionalmente, em
cada camada, que consiste numa arquitetura ponto-a-ponto de mĂłdulos que,
interagindo uns com os outros, fornecem uma visĂŁo global da disponibilidade
de recursos num ambiente distribuĂdo grande, dinĂąmico e heterogĂ©neo. O
modelo de descoberta de recursos proposto fornece a adaptabilidade e flexibilidade
para executar consultas complexas através do apoio a um conjunto
de caracterĂsticas significativas (tais como multi-dimensional, variedade e
consulta agregada) apoiadas por uma correspondĂȘncia exata e parcial, tanto
para o conteĂșdo de objetos estĂ©ticos e dinĂąmicos. SimulaçÔes mostram
que o HARD pode ser aplicado a escalas arbitrĂĄrias de dinamismo, tanto
em termos de complexidade como de escala, posicionando esta proposta
como uma arquitetura adequada para sistemas futuros de mĂșltiplos nĂșcleos.
TambĂ©m contribuĂmos com a proposta de um regime de gestĂŁo eficiente
dos recursos para sistemas futuros que podem utilizar recursos distribuĂos
de forma eficiente e de uma forma totalmente descentralizada. Além disso,
aproveitando componentes de descoberta (RR-RPs) permite que a nossa
plataforma de gestĂŁo de recursos encontre e aloque dinamicamente recursos
disponĂeis que garantam os parĂąmetros de QoS pedidos.Large scale distributed computing technologies such as Cloud, Grid, Cluster
and HPC supercomputers are progressing along with the revolutionary emergence
of many-core designs (e.g. GPU, CPUs on single die, supercomputers
on chip, etc.) and significant advances in networking and interconnect solutions.
In future, computing nodes with thousands of cores may be connected
together to form a single transparent computing unit which hides from applications
the complexity and distributed nature of these many core systems. In
order to efficiently benefit from all the potential resources in such large scale
many-core-enabled computing environments, resource discovery is the vital
building block to maximally exploit the capabilities of all distributed heterogeneous
resources through precisely recognizing and locating those resources
in the system. The efficient and scalable resource discovery is challenging for
such future systems where the resources and the underlying computation and
communication infrastructures are highly-dynamic, highly-hierarchical and
highly-heterogeneous. In this thesis, we investigate the problem of resource
discovery with respect to the general requirements of arbitrary scale future
many-core-enabled computing environments. The main contribution of this
thesis is to propose Hybrid Adaptive Resource Discovery (HARD), a novel
efficient and highly scalable resource-discovery approach which is built upon
a virtual hierarchical overlay based on self-organization and self-adaptation
of processing resources in the system, where the computing resources are
organized into distributed hierarchies according to a proposed hierarchical
multi-layered resource description model. Operationally, at each layer, it
consists of a peer-to-peer architecture of modules that, by interacting with
each other, provide a global view of the resource availability in a large,
dynamic and heterogeneous distributed environment. The proposed resource
discovery model provides the adaptability and flexibility to perform complex
querying by supporting a set of significant querying features (such as
multi-dimensional, range and aggregate querying) while supporting exact
and partial matching, both for static and dynamic object contents. The
simulation shows that HARD can be applied to arbitrary scales of dynamicity,
both in terms of complexity and of scale, positioning this proposal as a
proper architecture for future many-core systems. We also contributed to
propose a novel resource management scheme for future systems which
efficiently can utilize distributed resources in a fully decentralized fashion.
Moreover, leveraging discovery components (RR-RPs) enables our resource
management platform to dynamically find and allocate available resources
that guarantee the QoS parameters on demand
Semantic search and composition in unstructured peer-to-peer networks
This dissertation focuses on several research questions in the area of semantic search and composition in unstructured peer-to-peer (P2P) networks. Going beyond the state of the art, the proposed semantic-based search strategy S2P2P offers a novel path-suggestion based query routing mechanism, providing a reasonable tradeoff between search performance and network traffic overhead. In addition, the first semantic-based data replication scheme DSDR is proposed. It enables peers to use semantic information to select replica numbers and target peers to address predicted future demands. With DSDR, k-random search can achieve better precision and recall than it can with a near-optimal non-semantic replication strategy. Further, this thesis introduces a functional automatic semantic service composition method, SPSC. Distinctively, it enables peers to jointly compose complex workflows with high cumulative recall but low network traffic overhead, using heuristic-based bidirectional haining and service memorization mechanisms. Its query branching method helps to handle dead-ends in a pruned search space. SPSC is proved to be sound and a lower bound of is completeness is given. Finally, this thesis presents iRep3D for semantic-index based 3D scene selection in P2P search. Its efficient retrieval scales to answer hybrid queries involving conceptual, functional and geometric aspects. iRep3D outperforms previous representative efforts in terms of search precision and efficiency.Diese Dissertation bearbeitet Forschungsfragen zur semantischen Suche und Komposition in unstrukturierten Peer-to-Peer Netzen(P2P). Die semantische Suchstrategie S2P2P verwendet eine neuartige Methode zur Anfrageweiterleitung basierend auf PfadvorschlĂ€gen, welche den Stand der Wissenschaft ĂŒbertrifft. Sie bietet angemessene Balance zwischen Suchleistung und Kommunikationsbelastung im Netzwerk. AuĂerdem wird das erste semantische System zur Datenreplikation genannt DSDR vorgestellt, welche semantische Informationen berĂŒcksichtigt vorhergesagten zukĂŒnftigen Bedarf optimal im P2P zu decken. Hierdurch erzielt k-random-Suche bessere PrĂ€zision und Ausbeute als mit nahezu optimaler nicht-semantischer Replikation. SPSC, ein automatisches Verfahren zur funktional korrekten Komposition semantischer Dienste, ermöglicht es Peers, gemeinsam komplexe AblaufplĂ€ne zu komponieren. Mechanismen zur heuristischen bidirektionalen Verkettung und RĂŒckstellung von Diensten ermöglichen hohe Ausbeute bei geringer Belastung des Netzes. Eine Methode zur Anfrageverzweigung vermeidet das Feststecken in Sackgassen im beschnittenen Suchraum. Beweise zur Korrektheit und unteren Schranke der VollstĂ€ndigkeit von SPSC sind gegeben. iRep3D ist ein neuer semantischer Selektionsmechanismus fĂŒr 3D-Modelle in P2P. iRep3D beantwortet effizient hybride Anfragen unter BerĂŒcksichtigung konzeptioneller, funktionaler und geometrischer Aspekte. Der Ansatz ĂŒbertrifft vorherige Arbeiten bezĂŒglich PrĂ€zision und Effizienz