26 research outputs found
Specialized Lexicography, terminology and reference tools
Ce numéro spécial de Lingue & Linguaggi s’interroge sur certains aspects théoriques et pratiques concernant les termes appartenant aux domaines de l’économie et du droit et notamment sur leur inclusion dans des ressources monolingues ou bilingues consultées par des usagers experts et non experts, selon une pluralité d’approches théoriques et méthodologiques. À côté de l’aspect domanial économique ou juridique, les questions théoriques qui tissent un fil rouge entre les différents articles concernent les aspects suivants: la réflexion autour de la définition des termes; le support que les corpus peuvent fournir à une représentation du sens tenant compte des objectifs spécifiques des usagers ciblés par les ressources elles-mêmes; l’utilité de la terminologie en tant qu’instrument cognitif apte à la structuration et à la dénomination de nouvelles idées dans des domaines spécialisés; les avantages ou les désavantages apportés par la facilité et la rapidité d’accès aux nombreuses ressources sur la Toile de la part du public – expert, semi expert ou profane
Mobile Ad-Hoc Networks
Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks
Protecting applications using trusted execution environments
While cloud computing has been broadly adopted, companies that deal with sensitive data are still reluctant to do so due to privacy concerns or legal restrictions. Vulnerabilities in complex cloud infrastructures, resource sharing among tenants, and malicious insiders pose a real threat to the confidentiality and integrity of sensitive customer data. In recent years trusted execution environments (TEEs), hardware-enforced isolated regions that can protect code and data from the rest of the system, have become available as part of commodity CPUs. However, designing applications for the execution within TEEs requires careful consideration of the elevated threats that come with running in a fully untrusted environment. Interaction with the environment should be minimised, but some cooperation with the untrusted host is required, e.g. for disk and network I/O, via a host interface. Implementing this interface while maintaining the security of sensitive application code and data is a fundamental challenge.
This thesis addresses this challenge and discusses how TEEs can be leveraged to secure existing applications efficiently and effectively in untrusted environments. We explore this in the context of three systems that deal with the protection of TEE applications and their host interfaces:
SGX-LKL is a library operating system that can run full unmodified applications within TEEs with a minimal general-purpose host interface. By providing broad system support inside the TEE, the reliance on the untrusted host can be reduced to a minimal set of low-level operations that cannot be performed inside the enclave. SGX-LKL provides transparent protection of the host interface and for both disk and network I/O.
Glamdring is a framework for the semi-automated partitioning of TEE applications into an untrusted and a trusted compartment. Based on source-level annotations, it uses either dynamic or static code analysis to identify sensitive parts of an application. Taking into account the objectives of a small TCB size and low host interface complexity, it defines an application-specific host interface and generates partitioned application code.
EnclaveDB is a secure database using Intel SGX based on a partitioned in-memory database engine. The core of EnclaveDB is its logging and recovery protocol for transaction durability. For this, it relies on the database log managed and persisted by the untrusted database server. EnclaveDB protects against advanced host interface attacks and ensures the confidentiality, integrity, and freshness of sensitive data.Open Acces
Asynchronous epidemic algorithms for consistency in large-scale systems
Achieving and detecting a globally consistent state is essential to many services in the large
and extreme-scale distributed systems, especially when the desired consistent state is critical
for services operation. Centralised and deterministic approaches for synchronisation and
distributed consistency are not scalable and not fault-tolerant. Alternatively, epidemic-based
paradigms are decentralised computations based on randomised communications. They are
scalable, resilient, fault-tolerant, and converge to the desired target in logarithmic time with
respect to system size. Thus, many distributed services have adopted epidemic protocols
to achieve the consensus and the consistent state, mainly due to scalability concerns. The
convergence of epidemic protocols is stochastically guaranteed. However, the detection of
the convergence is probabilistic and non-explicit. In a real-world environment, systems are
unreliable, and epidemic protocols cannot converge to the desired state. Thus, achieving
convergence by itself does not ensure making a system-wide consistent state under dynamic
conditions.
The research work presented in this thesis introduces the Phase Transition Algorithm
(PTA) to achieve distributed consistent state based on the explicit detection of convergence.
Each phase in PTA is a decentralised decision-making process that implements epidemic data
aggregation, in which the detection of convergence implies achieving a global agreement. The
phases in PTA can be cascaded to achieve higher certainty as desired. Following the PTA,
two epidemic protocols, namely PTP and ECP, are proposed to acquire of consensus, i.e. for
the consistency in data dissemination and data aggregation. The protocols are examined
through simulations, and experimental results have validated the protocols ability to achieve
and explicitly detect the consensus among system nodes.
The research work has also studied the epidemic data aggregation under nodes churn and
network failures, in which the analysis has identified three phases of the aggregation process.
The investigations have shown a different impact of nodes churn on each phase. The phase
that is critical for the aggregation process has been studied further, which led to propose
new robust data aggregation protocols, REAP and REAP+. Each protocol has a different
decentralised replication method, and both implements distributed failure detection and
instantaneous mass restoration mechanisms. Simulations have validated the protocols, and
results have shown protocols ability to converge, detect convergence, and produce competitive
accuracy under various levels of nodes churn.
Furthermore, distributed consistency in continuous systems is addressed in the research.
The work has proposed a novel continuous epidemic protocol with the adaptive restart
mechanism. The protocol restarts either upon the detection of system convergence or upon
the detection of divergence. Also, the protocol introduces the seed selection method for
the peak data distribution in decentralised approaches, which was a challenge that requires
single-point initialisation and leader-election step. The simulations validated the performance
of the algorithm under static and dynamic conditions and approved that convergence and
divergence detection accuracy can be tuned as desired.
Finally, the research work shows that combining and integrating of the proposed protocols
enables extreme-scale distributed systems to achieve and detect global consistent states even
under realistic and dynamical conditions
State management in coreless mobile networks
The number of mobile Internet users has skyrocketed and with the advent of the Internet of things we are reaching the limits of the current telecommunications standard 4G. The improvements and goals set for the next standard, 5G, are not trivial and research is in progress to reach them. Improvements across all involved technology fields is needed.
In this thesis we present a novel mobile network architecture-coreless mobile networks- and develop state management concepts, which we base on the analysis of the current 4G/LTE architecture. The coreless mobile network focuses on the redesign of the state management in mobile networks, more precisely, removal of state from 4G core network entities into an eternal ubiquitous data store. The architecture follows trends in current research, particularly network function virtualisation, software defined networking and mobile edge computing.
The new network architecture requires a data storage solution that is capable of functioning as the state store in the mobile network environment. Thus, we present an overview of promising data stores and evaluate their suitability. Further in this thesis we present the results of benchmarking the Apache Geode data store, as an example of a state management solution that could be leveraged in realising the coreless mobile network architecture. We discovered that the Apache Geode data store is, depending on configuration, capable of delivering the data model, consistency, high availability, scaling, throughput and latency that are required in our proposed architecture.
ACM Computing Classification System (CCS):
- Information systems ~ Distributed storage
- Information systems ~ Hierarchical storage management
- Networks ~ Middle boxes / network appliances
- Networks ~ Mobile network
In-Production Continuous Testing for Future Telco Cloud
Software Defined Networking (SDN) is an emerging paradigm to design, build and operate networks. The driving motivation of SDN was the need for a major change in network technologies to support a configuration, management, operation, reconfiguration and evolution than in current computer networks. In the SDN world, performance it is not only related to the behaviour of the data plane. As the separation of control plane and data plane makes the latter significantly more agile, it lays off all the complex processing workload to the control plane. This is further exacerbated in distributed network controller, where the control plane is additionally loaded with the state synchronization overhead. Furthermore, the introduction of SDNs technologies has raised advanced challenges in achieving failure resilience, meant as the persistence of service delivery that can justifiably be trusted, when facing changes, and fault tolerance, meant as the ability to avoid service failures in the presence of faults.
Therefore, along with the “softwarization” of network services, it is an important goal in the engineering of such services, e.g. SDNs and NFVs, to be able to test and assess the proper functioning not only in emulated conditions before release and deployment, but also “in-production”, when the system is under real operating conditions.
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The goal of this thesis is to devise an approach to evaluate not only the performance, but also the effectiveness of the failure detection, and mitigation mechanisms provided by SDN controllers, as well as the capability of the SDNs to ultimately satisfy nonfunctional requirements, especially resiliency, availability, and reliability. The approach consists of exploiting benchmarking techniques, such as the failure injection, to get continuously feedback on the performance as well as capabilities of the SDN services to survive failures, which is of paramount importance to improve the effective- ness of the system internal mechanisms in reacting to anomalous situations potentially occurring in operation, while its services are regularly updated or improved.
Within this vision, this dissertation first presents SCP-CLUB (SDN Control Plane CLoUd-based Benchmarking), a benchmarking frame- work designed to automate the characterization of SDN control plane performance, resilience and fault tolerance in telco cloud deployments. The idea is to provide the same level of automation available in deploying NFV function, for the testing of different configuration, using idle cycles of the telco cloud infrastructure. Then, the dissertation proposes an extension of the framework with mechanisms to evaluate the runtime behaviour of a Telco Cloud SDN under (possibly unforeseen) failure conditions, by exploiting the software failure injection
An evaluation of non-relational database management systems as suitable storage for user generated text-based content in a distributed environment
Non-relational database management systems address some of the limitations relational database management systems have when storing large volumes of unstructured, user generated text-based data in distributed environments. They follow different approaches through the data model they use, their ability to scale data storage over distributed servers and the programming interface they provide.
An experimental approach was followed to measure the capabilities these alternative database management systems present in their approach to address the limitations of relational databases in terms of their capability to store unstructured text-based data, data warehousing capabilities, ability to scale data storage across distributed servers and the level of programming abstraction they provide.
The results of the research highlighted the limitations of relational database management systems. The different database management systems do address certain limitations, but not all. Document-oriented databases provide the best results and successfully address the need to store large volumes of user generated text-based data in a distributed environmentSchool of ComputingM. Sc. (Computer Science
Factors Influencing Customer Satisfaction towards E-shopping in Malaysia
Online shopping or e-shopping has changed the world of business and quite a few people have
decided to work with these features. What their primary concerns precisely and the responses from
the globalisation are the competency of incorporation while doing their businesses. E-shopping has
also increased substantially in Malaysia in recent years. The rapid increase in the e-commerce
industry in Malaysia has created the demand to emphasize on how to increase customer satisfaction
while operating in the e-retailing environment. It is very important that customers are satisfied with
the website, or else, they would not return. Therefore, a crucial fact to look into is that companies
must ensure that their customers are satisfied with their purchases that are really essential from the ecommerce’s
point of view. With is in mind, this study aimed at investigating customer satisfaction
towards e-shopping in Malaysia. A total of 400 questionnaires were distributed among students
randomly selected from various public and private universities located within Klang valley area.
Total 369 questionnaires were returned, out of which 341 questionnaires were found usable for
further analysis. Finally, SEM was employed to test the hypotheses. This study found that customer
satisfaction towards e-shopping in Malaysia is to a great extent influenced by ease of use, trust,
design of the website, online security and e-service quality. Finally, recommendations and future
study direction is provided.
Keywords: E-shopping, Customer satisfaction, Trust, Online security, E-service quality, Malaysia
Design and Implementation of a Distributed Mobility Management Entity (MME) on OpenStack
Network Functions Virtualisation (NFV) involves the implementation of network functions, for example firewalls and routers, as software applications that can run on general-purpose servers. In present-day networks, each network function is typically implemented on dedicated and proprietary hardware. By utilising virtualisation technologies, NFV enables network functions to be deployed on cloud computing infrastructure in data centers.
This thesis discusses the application of NFV to the Evolved Packet Core (EPC) in Long Term Evolution (LTE) networks; specifically to the Mobility Management Entity (MME), a control plane entity in the EPC. With the convergence of cloud computing and mobile networks, conventional architectures of network elements need to be re-designed in order to fully harness benefits such as scalability and elasticity. To this end, we design and implement a distributed MME with a three-tier architecture common to web applications. We highlight design considerations for moving MME functionality to the cloud and compare our new distributed design to that of a standalone MME. We deploy and test the distributed MME on two separate OpenStack clouds. Our results indicate that the benefits of scalability and resilience can outweigh the marginal increase in latency for EPC procedures. We find that the latency is dependent on the actual placement of MME components within the data center. Also, we believe that extensions to the OpenStack platform are required before it can meet performance and availability requirements for telecommunication applications