93 research outputs found
An Autonomic Cross-Platform Operating Environment for On-Demand Internet Computing
The Internet has evolved into a global and ubiquitous communication medium interconnecting powerful application servers, diverse desktop computers and mobile notebooks. Along with recent developments in computer technology, such as the convergence of computing and communication devices, the way how people use computers and the Internet has changed peopleÂŽs working habits and has led to new application scenarios. On the one hand, pervasive computing, ubiquitous computing and nomadic computing become more and more important since different computing devices like PDAs and notebooks may be used concurrently and alternately, e.g. while the user is on the move. On the other hand, the ubiquitous availability and pervasive interconnection of computing systems have fostered various trends towards the dynamic utilization and spontaneous collaboration of available remote computing resources, which are addressed by approaches like utility computing, grid computing, cloud computing and public computing. From a general point of view, the common objective of this development is the use of Internet applications on demand, i.e. applications that are not installed in advance by a platform administrator but are dynamically deployed and run as they are requested by the application user. The heterogeneous and unmanaged nature of the Internet represents a major challenge for the on demand use of custom Internet applications across heterogeneous hardware platforms, operating systems and network environments. Promising remedies are autonomic computing systems that are supposed to maintain themselves without particular user or application intervention. In this thesis, an Autonomic Cross-Platform Operating Environment (ACOE) is presented that supports On Demand Internet Computing (ODIC), such as dynamic application composition and ad hoc execution migration. The approach is based on an integration middleware called crossware that does not replace existing middleware but operates as a self-managing mediator between diverse application requirements and heterogeneous platform configurations. A Java implementation of the Crossware Development Kit (XDK) is presented, followed by the description of the On Demand Internet Computing System (ODIX). The feasibility of the approach is shown by the implementation of an Internet Application Workbench, an Internet Application Factory and an Internet Peer Federation. They illustrate the use of ODIX to support local, remote and distributed ODIC, respectively. Finally, the suitability of the approach is discussed with respect to the support of ODIC
Live migration of user environments across wide area networks
A complex challenge in mobile computing is to allow the user to migrate her highly customised environment while moving to a different location and to continue work without interruption. I motivate why this is a highly desirable capability and conduct a survey of the current approaches towards this goal and explain their limitations. I then propose a new architecture to support user mobility by live migration of a userâs operating system instance over the network. Previous work includes the Collective and Internet Suspend/Resume projects that have addressed migration of a userâs environment by suspending the running state and resuming it at a later time. In contrast to previous work, this work addresses live migration of a userâs operating system instance across wide area links. Live migration is done by performing most of the migration while the operating system is still running, achieving very little downtime and preserving all network connectivity.
I developed an initial proof of concept of this solution. It relies on migrating whole operating systems using the Xen virtual machine and provides a way to perform live migration of persistent storage as well as the network connections across subnets. These challenges have not been addressed previously in this scenario. In a virtual machine environment, persistent storage is provided by virtual block devices. The architecture supports decentralized virtual block device replication across wide area network links, as well as migrating network connection across subnetworks using the Host Identity Protocol. The proposed architecture is compared against existing solutions and an initial performance evaluation of the prototype implementation is presented, showing that such a solution is a promising step towards true seamless mobility of fully fledged computing environments
Cloud-edge hybrid applications
Many modern applications are designed to provide interactions among users, including multi-
user games, social networks and collaborative tools. Users expect application response time to
be in the order of milliseconds, to foster interaction and interactivity.
The design of these applications typically adopts a client-server model, where all interac-
tions are mediated by a centralized component. This approach introduces availability and fault-
tolerance issues, which can be mitigated by replicating the server component, and even relying on
geo-replicated solutions in cloud computing infrastructures. Even in this case, the client-server
communication model leads to unnecessary latency penalties for geographically close clients and
high operational costs for the application provider.
This dissertation proposes a cloud-edge hybrid model with secure and ecient propagation
and consistency mechanisms. This model combines client-side replication and client-to-client
propagation for providing low latency and minimizing the dependency on the server infras-
tructure, fostering availability and fault tolerance. To realize this model, this works makes the
following key contributions.
First, the cloud-edge hybrid model is materialized by a system design where clients maintain
replicas of the data and synchronize in a peer-to-peer fashion, and servers are used to assist
clientsâ operation. We study how to bring most of the application logic to the client-side, us-
ing the centralized service primarily for durability, access control, discovery, and overcoming
internetwork limitations.
Second, we dene protocols for weakly consistent data replication, including a novel CRDT
model (â-CRDTs). We provide a study on partial replication, exploring the challenges and
fundamental limitations in providing causal consistency, and the diculty in supporting client-
side replicas due to their ephemeral nature.
Third, we study how client misbehaviour can impact the guarantees of causal consistency.
We propose new secure weak consistency models for insecure settings, and algorithms to enforce
such consistency models.
The experimental evaluation of our contributions have shown their specic benets and
limitations compared with the state-of-the-art. In general, the cloud-edge hybrid model leads to
faster application response times, lower client-to-client latency, higher system scalability as fewer clients need to connect to servers at the same time, the possibility to work oine or disconnected
from the server, and reduced server bandwidth usage.
In summary, we propose a hybrid of cloud-and-edge which provides lower user-to-user la-
tency, availability under server disconnections, and improved server scalability â while being
ecient, reliable, and secure.Muitas aplicaçÔes modernas são criadas para fornecer interaçÔes entre utilizadores, incluindo
jogos multiutilizador, redes sociais e ferramentas colaborativas. Os utilizadores esperam que o
tempo de resposta nas aplicaçÔes seja da ordem de milissegundos, promovendo a interação e
interatividade.
A arquitetura dessas aplicaçÔes normalmente adota um modelo cliente-servidor, onde todas as
interaçÔes são mediadas por um componente centralizado. Essa abordagem apresenta problemas
de disponibilidade e tolerùncia a falhas, que podem ser mitigadas com replicação no componente
do servidor, até com a utilização de soluçÔes replicadas geogracamente em infraestruturas de
computação na nuvem. Mesmo neste caso, o modelo de comunicação cliente-servidor leva a
penalidades de latĂȘncia desnecessĂĄrias para clientes geogracamente prĂłximos e altos custos
operacionais para o provedor das aplicaçÔes.
Esta dissertação propĂ”e um modelo hĂbrido cloud-edge com mecanismos seguros e ecientes
de propagação e consistĂȘncia. Esse modelo combina replicação do lado do cliente e propagação
de cliente para cliente para fornecer baixa latĂȘncia e minimizar a dependĂȘncia na infraestrutura
do servidor, promovendo a disponibilidade e tolerĂąncia a falhas. Para realizar este modelo, este
trabalho faz as seguintes contribuiçÔes principais.
Primeiro, o modelo hĂbrido cloud-edge Ă© materializado por uma arquitetura do sistema em
que os clientes mantĂȘm rĂ©plicas dos dados e sincronizam de maneira ponto a ponto e onde os
servidores são usados para auxiliar na operação dos clientes. Estudamos como trazer a maior
parte da lógica das aplicaçÔes para o lado do cliente, usando o serviço centralizado principalmente
para durabilidade, controlo de acesso, descoberta e superação das limitaçÔes inter-rede.
Em segundo lugar, denimos protocolos para replicação de dados fracamente consistentes,
incluindo um novo modelo de CRDTs (â-CRDTs). Fornecemos um estudo sobre replicação parcial,
explorando os desaos e limitaçÔes fundamentais em fornecer consistĂȘncia causal e a diculdade
em suportar réplicas do lado do cliente devido à sua natureza efémera.
Terceiro, estudamos como o mau comportamento da parte do cliente pode afetar as garantias
da consistĂȘncia causal. Propomos novos modelos seguros de consistĂȘncia fraca para conguraçÔes
inseguras e algoritmos para impor tais modelos de consistĂȘncia.
A avaliação experimental das nossas contribuiçÔes mostrou os benefĂcios e limitaçÔes em comparação com o estado da arte. Em geral, o modelo hĂbrido cloud-edge leva a tempos de resposta
nas aplicaçÔes mais rĂĄpidos, a uma menor latĂȘncia de cliente para cliente e Ă possibilidade de
trabalhar oine ou desconectado do servidor. Adicionalmente, obtemos uma maior escalabilidade
do sistema, visto que menos clientes precisam de estar conectados aos servidores ao mesmo tempo
e devido à redução na utilização da largura de banda no servidor.
Em resumo, propomos um modelo hĂbrido entre a orla (edge) e a nuvem (cloud) que fornece
menor latĂȘncia entre utilizadores, disponibilidade durante desconexĂ”es do servidor e uma melhor
escalabilidade do servidor â ao mesmo tempo que Ă© eciente, conĂĄvel e seguro
Migration and load-balancing in distributed hierarchical component systems
VyvĂĄĆŸenĂ© vyuĆŸitĂ zdrojĆŻ je jednĂm z cĂlĆŻ distribuovanĂœch aplikacĂ. Jeden ze zpĆŻsobĆŻ, jak dosĂĄhnou vyvĂĄĆŸenĂ©ho vyuĆŸitĂ je monitorovĂĄnĂ bÄhu aplikacĂ a migrace jejich komponent mezi poÄĂtaÄi. Migrace s sebou pĆinĂĄĆĄĂ mnoho otĂĄzek, od monitorovĂĄnĂ prostĆedkĆŻ aĆŸ po zĂskĂĄvĂĄnĂ stavu komponenty a jeho pĆenosu na jinĂœ poÄĂtaÄ. CĂlem tĂ©to prĂĄce je navrhnout a implementovat podporu pro migraci a vyvaĆŸovĂĄnĂ zĂtÄĆŸe v hierarchickĂ©m komponentovĂ©m systĂ©mu SOFA 2.A well balanced usage of resources is one of the goals of distributed applications. A way to achieve such a balanced usage is by run-time monitoring and migration of components of already executed applications between computers. There are many issues related to migration, from monitoring resources usage till obtaining component state and transferring to a di erent computer. The goal of this thesis is to design and implement a support for migration and load-balancing of components in the SOFA 2 hierarchical component system.Department of Software EngineeringKatedra softwarovĂ©ho inĆŸenĂœrstvĂFaculty of Mathematics and PhysicsMatematicko-fyzikĂĄlnĂ fakult
Contributions to Vehicular Communications Systems and Schemes
La derniÚre décennie a marqué une grande hausse des applications véhiculaires comme une nouvelle source de revenus et un facteur de distinction dans l'industrie des véhicules. Ces applications véhiculaires sont classées en deux groupes : les applications de sécurité et les
applications d'info divertissement. Le premier groupe inclue le changement intelligent de voie, l'avertissement de dangers de routes et la prévention coopérative de collision qui comprend la vidéo sur demande (VoD), la diffusion en direct, la diffusion de météo et de nouvelles et les jeux
interactifs. Cependant, Il est à noter que d'une part, les applications véhiculaires d'info divertissement nécessitent une bande passante élevée et une latence relativement faible ; D'autre part, les applications de sécurité requiÚrent exigent un délai de bout en bout trÚs bas et un canal de
communication fiable pour la livraison des messages d'urgence. Pour satisfaire le besoin en applications efficaces, les fabricants de véhicules ainsi que la
communautĂ© acadĂ©mique ont introduit plusieurs applications Ă lâintĂ©rieur de vĂ©hicule et entre vĂ©hicule et vĂ©hicule (V2V). Sauf que, l'infrastructure du rĂ©seau sans fil n'a pas Ă©tĂ© conçue pour gĂ©rer les applications de vĂ©hicules, en raison de la haute mobilitĂ© des vĂ©hicules, de l'imprĂ©visibilitĂ©
du comportement des conducteurs et des modÚles de trafic dynamiques. La relÚve est l'un des principaux défis des réseaux de véhicules, car la haute mobilité exige au
réseau sans fil de faire la relÚve en un trÚs court temps. De plus, l'imprévisibilité du comportement du conducteur cause l'échec des protocoles proactifs traditionnels de relÚve, car la prédiction du prochain routeur peut changer en fonction de la décision du conducteur. Aussi, le réseau de véhicules peut subir une mauvaise qualité de service dans les régions de relÚve en raison d'obstacles naturels, de véhicules de grande taille ou de mauvaises conditions météorologiques. Cette thÚse se concentre sur la relÚve dans l'environnement des véhicules et son effet sur les
applications vĂ©hiculaires. Nous proposons des solutions pratiques pour les rĂ©seaux actuellement dĂ©ployĂ©s, principalement les rĂ©seaux LTE, l'infrastructure vĂ©hicule Ă vĂ©hicule (V2V) ainsi que les outils efficaces dâĂ©mulateurs de relĂšves dans les rĂ©seaux vĂ©hiculaires.----------ABSTRACT: The last decade marked the rise of vehicular applications as a new source of revenue and a key differentiator in the vehicular industry. Vehicular Applications are classified into safety and infotainment applications. The former include smart lane change, road hazard warning, and
cooperative collision avoidance; however, the latter include Video on Demand (VoD), live streaming, weather and news broadcast, and interactive games. On one hand, infotainment
vehicular applications require high bandwidth and relatively low latency; on the other hand, safety applications requires a very low end to end delay and a reliable communication channel to deliver emergency messages. To satisfy the thirst for practical applications, vehicle manufacturers along with research institutes introduced several in-vehicle and Vehicle to Vehicle (V2V) applications. However, the wireless
network infrastructure was not designed to handle vehicular applications, due to the high mobility of vehicles, unpredictability of driversâ behavior, and dynamic traffic patterns. Handoff is one of the main challenges of vehicular networks since the high mobility puts pressure on the wireless network to finish the handoff within a short period. Moreover, the unpredictability of driver behavior causes the traditional proactive handoff protocols to fail, since the prediction of the next router may change based on the driverâs decision. Moreover, the vehicular network may
suffer from bad Quality of Service (QoS) in the regions of handoff due to natural obstacles, large vehicles, or weather conditions. This thesis focuses on the handoff on the vehicular environment and its effect on the vehicular
applications. We consider practical solutions for the currently deployed networks mainly Long Term Evolution (LTE) networks, the Vehicle to Vehicle (V2V) infrastructure, and the tools that can be used effectively to emulate handoff on the vehicular networks
Telecommunications Networks
This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing
Concepts for an intuitive user interface for DLNA using NFC technology
Consumption of digital media is dramatically increased by the development of conventional connectivity technologies and the advent of home entertainment appliances. The evolution of networking technology, hardware development and advanced services leads to an increased sophistication of device manipulation and long learning curves for average users. DLNA standardizes the interoperablity between media devices over a framework. With the help of personal handheld devices and smart phones, a ubiquitous media network is formed at home or on the road. NFC is a radio technology bridging physical and digital world, which is now widely deployed in a varied number of application scenarios to ease Human-Computer Interaction. This master thesis proposes a system architecture based on the confluence of DLNA architecture and NFC technology to facilitate simple, intuitive and impromptu interaction with media devices. This NFC-enabled DLNA Communication system architecture defines a communication model which delivers the vision of NFC as the enabler of DLNA control and communication, a network model, a set of diverse device functional components, a set of dedicated devices and baseline principles of system architecture. Based on the generic system architecture, a research is explored on A/V and image media sharing, UI retrieval, media uploading/downloading and print document application fields. Six use cases are proposed, they share the properties and principles defined in the system architecture and additionally they maintain their own use case specific features and their proprietary NFC data formats. Among them two use cases are explained in more detail. One use case, A/V Handover, delivers a consistent "tap and exchange" scenario. The other use case, Control Handover, grants users an instantaneous access to the control UI. A prototype implementation between smart devices or home appliances are presented showcasing an instantaneous, rapid and spontaneous media sharing and management application. Following the design paradigm presented in this thesis, more use cases in specific application fields are easily to be implemented
Towards Implicit Parallel Programming for Systems
Multi-core processors require a program to be decomposable into independent parts that can execute in parallel in order to scale performance with the number of cores. But parallel programming is hard especially when the program requires state, which many system programs use for optimization, such as for example a cache to reduce disk I/O. Most prevalent parallel programming models do not support a notion of state and require the programmer to synchronize state access manually, i.e., outside the realms of an associated optimizing compiler. This prevents the compiler to introduce parallelism automatically and requires the programmer to optimize the program manually.
In this dissertation, we propose a programming language/compiler co-design to provide a new programming model for implicit parallel programming with state and a compiler that can optimize the program for a parallel execution.
We define the notion of a stateful function along with their composition and control structures. An example implementation of a highly scalable server shows that stateful functions smoothly integrate into existing programming language concepts, such as object-oriented programming and programming with structs. Our programming model is also highly practical and allows to gradually adapt existing code bases. As a case study, we implemented a new data processing core for the Hadoop Map/Reduce system to overcome existing performance bottlenecks. Our lambda-calculus-based compiler automatically extracts parallelism without changing the program's semantics. We added further domain-specific semantic-preserving transformations that reduce I/O calls for microservice programs. The runtime format of a program is a dataflow graph that can be executed in parallel, performs concurrent I/O and allows for non-blocking live updates
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