Social Network Analysis

The organization of behavior: A neuropsychological theory

National Institute of Standards and Technology における超伝導研究及び生活

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A Break in the Clouds: Towards a Cloud Definition

The paradigm of Internet of Things (IoT) is paving the way for a world, where many of our daily objects will be interconnected and will interact with their environment in order to collect information and automate certain tasks. Such a vision requires, among other things, seamless authentication, data privacy, security, robustness against attacks, easy deployment, and self-maintenance. Such features can be brought by blockchain, a technology born with a cryptocurrency called Bitcoin. In this paper, a thorough review on how to adapt blockchain to the specific needs of IoT in order to develop Blockchain-based IoT (BIoT) applications is presented. After describing the basics of blockchain, the most relevant BIoT applications are described with the objective of emphasizing how blockchain can impact traditional cloud-centered IoT applications. Then, the current challenges and possible optimizations are detailed regarding many aspects that affect the design, development, and deployment of a BIoT application. Finally, some recommendations are enumerated with the aim of guiding future BIoT researchers and developers on some of the issues that will have to be tackled before deploying the next generation of BIoT applications.

A Review on the Use of Blockchain for the Internet of Things

The use of utility on-demand computing infrastructures, such as Amazon's Elastic Clouds [1], is a viable solution to speed lengthy parallel computing problems to those without access to other cluster or grid infrastructures. With a suitable middleware, bag-of-tasks problems could be easily deployed over a pool of virtual computers created on such infrastructures.In bag-of-tasks problems, as there is no communication between tasks, the number of concurrent tasks is allowed to vary over time. In a utility computing infrastructure, if too many virtual computers are created, the speedups are high but may not be cost effective; if too few computers are created, the cost is low but speedups fall below expectations. Without previous knowledge of the processing time of each task, it is difficult to determine how many machines should be created.In this paper, we present an heuristic to optimize the number of machines that should be allocated to process tasks so that for a given budget the speedups are maximal. We have simulated the proposed heuristics against real and theoretical workloads and evaluated the ratios between number of allocated hosts, charged times, speedups and processing times. With the proposed heuristics, it is possible to obtain speedups in line with the number of allocated computers, while being charged approximately the same predefined budget.

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Heuristic for resources allocation on utility computing infrastructures

This paper presents Rubah, the first dynamic software updating system for Java that: is portable, implemented via libraries and bytecode rewriting on top of a standard JVM; is efficient, imposing essentially no overhead on normal, steady-state execution; is flexible, allowing nearly arbitrary changes to classes between updates; and isnon-disruptive, employing either a novel eager algorithm that transforms the program state with multiple threads, or a novel lazy algorithm that transforms objects as they are demanded, post-update. Requiring little programmer effort, Rubah has been used to dynamically update five long-running applications: the H2 database, the Voldemort key-value store, the Jake2 implementation of the Quake 2 shooter game, the CrossFTP server, and the JavaEmailServer.

/pdf/rubah-dsu-for-java-on-a-stock-jvm-5djkb9v7rr.pdf

Rubah: DSU for Java on a stock JVM

Developing distributed multiplayer games for ad-hoc networks is challenging. Consistency of the replicated shared state is hard to ensure at a low cost. Current consistency models and middleware systems lack the required adaptability and efficiency when applied to ad-hoc gaming. Hence, developing such robust applications is still a daunting task. We propose i) Vector-Field Consistency (VFC), a new consistency model, and ii) the Mobihoc middleware to ease the programming effort of these games, while ensuring the consistency of replicated objects. VFC unifies i) several forms of consistency enforcement and a multi-dimensional criteria (time, sequence and value) to limit replica divergence, with ii) techniques based on locality-awareness (w.r.t. players position). Mobihoc adopts VFC and provides game programmers the abstractions to manage game state easily and efficiently. A Mobihoc prototype and a demonstrating game were developed and evaluated. The results obtained are very encouraging.

/pdf/vector-field-consistency-for-ad-hoc-gaming-35ra31dgyw.pdf

Vector-field consistency for ad-hoc gaming

Community networks (CNs) have gained momentum in the last few years with the increasing number of spontaneously deployed WiFi hotspots and home networks. These networks, owned and managed by volunteers, offer various services to their members and to the public. While Internet access is the most popular service, the provision of services of local interest within the network is enabled by the emerging technology of CN micro-clouds. By putting services closer to users, micro-clouds pursue not only a better service performance, but also a low entry barrier for the deployment of mainstream Internet services within the CN. Unfortunately, the provisioning of these services is not so simple. Due to the large and irregular topology, high software and hardware diversity of CNs, a “careful” placement of micro-clouds services over the network is required to optimize service performance. This paper proposes to leverage state information about the network to inform service placement decisions, and to do so through a fast heuristic algorithm, which is critical to quickly react to changing conditions. To evaluate its performance, we compare our heuristic with one based on random placement in Guifi.net, the biggest CN worldwide. Our experimental results show that our heuristic consistently outperforms random placement by 2x in bandwidth gain. We quantify the benefits of our heuristic on a real live video-streaming service, and demonstrate that video chunk losses decrease significantly, attaining a 37% decrease in the packet loss rate. Further, using a popular Web 2.0 service, we demonstrate that the client response times decrease up to an order of magnitude when using our heuristic. Since these improvements translate in the QoE (Quality of Experience) perceived by the user, our results are relevant for contributing to higher QoE, a crucial parameter for using services from volunteer-based systems and adapting CN micro-clouds as an eco-system for service deployment.

/pdf/a-lightweight-service-placement-approach-for-community-4d2dsy5bd7.pdf

A lightweight service placement approach for community network micro-clouds

Community networks (CNs) have gained momentum in the last few years with the increasing number of spontaneously deployed WiFi hotspots and home networks. These networks, owned and managed by volunteers, offer various services to their members and to the public. To reduce the complexity of service deployment, community micro-clouds have recently emerged as a promising enabler for the delivery of cloud services to community users. By putting services closer to consumers, micro-clouds pursue not only a better service performance, but also a low entry barrier for the deployment of mainstream Internet services within the CN. Unfortunately, the provisioning of the services is not so simple. Due to the large and irregular topology, high software and hardware diversity of CNs, it requires of a "careful" placement of micro-clouds and services over the network. To achieve this, this paper proposes to leverage state information about the network to inform service placement decisions, and to do so through a fast heuristic algorithm, which is vital to quickly react to changing conditions. To evaluate its performance, we compare our heuristic with one based on random placement in Guifi.net, the biggest CN worldwide. Our experimental results show that our heuristic consistently outperforms random placement by 211% in terms of bandwidth gain. We quantify the benefits of our heuristic on a real live video-streaming service, and demonstrate that video chunk losses decrease significantly, attaining a 37% decrease in the loss packet rate. Further, using a popular Web 2.0 service, we demonstrate that the client response times decrease up to an order of magnitude when using our heuristic.

/pdf/practical-service-placement-approach-for-microservices-gdxcqd1y12.pdf

Luís Veiga

Papers

Heuristic for resources allocation on utility computing infrastructures

Rubah: DSU for Java on a stock JVM

Vector-field consistency for ad-hoc gaming

A lightweight service placement approach for community network micro-clouds

Practical Service Placement Approach for Microservices Architecture