Antonio Puliafito

Performance and Reliability Analysis of Computer Systems

Table of

Combining Cloud and sensors in a smart city environment

In the current worldwide ICT scenario, a constantly growing number of ever more powerful devices (smartphones, sensors, household appliances, RFID devices, etc.) join the Internet, significantly impacting the global traffic volume (data sharing, voice, multimedia, etc.) and foreshadowing a world of (more or less) smart devices, or “things” in the Internet of Things (IoT) perspective. Heterogeneous resources can be aggregated and abstracted according to tailored thing-like semantics, thus enabling Things as a Service paradigm, or better a “Cloud of Things”. In the Future Internet initiatives, sensor networks will assume even more of a crucial role, especially for making smarter cities. Smarter sensors will be the peripheral elements of a complex future ICT world. However, due to differences in the “appliances” being sensed, smart sensors are very heterogeneous in terms of communication technologies, sensing features and elaboration capabilities. This article intends to contribute to the design of a pervasive infrastructure where new generation services interact with the surrounding environment, thus creating new opportunities for contextualization and geo-awareness. The architecture proposal is based on Sensor Web Enablement standard specifications and makes use of the Contiki Operating System for accomplishing the IoT. Smart cities are assumed as the reference scenario.

Volunteer Computing and Desktop Cloud: The Cloud@Home Paradigm

Only commercial Cloud solutions have been implemented so far, offering computing resources and services for renting. Some interesting projects, such as Nimbus, OpenNEbula, Reservoir, work on Cloud. One of their aims is to provide a Cloud infrastructure able to provide and share resources and services for scientific purposes. The encouraging results of Volunteer computing projects in this context and the flexibility of the Cloud, suggested to address our research efforts towards a combined new computing paradigm we named Cloud@Home.On one hand it can be considered as a generalization of the @homephilosophy, knocking down the barriers of Volunteer computing, and also allowing to share more general services. On the other hand,Cloud@Home can be considered as the enhancement of the grid-utility vision of Cloud computing. In this new paradigm, users’ hosts are not passive interface to Cloud services anymore, but they can interact (free or by charge) with other Clouds.In this paper we present the Cloud@Home paradigm, highlighting its contribution to the actual state of the art on the topic of distributed and Cloud computing. We detail the functional architecture and the core structure implementing such paradigm, demonstrating how it is really possible to build up a Cloud@Home infrastructure.

Using mobile agents to implement flexible network management strategies

Due to their intrinsic complexity, computer and communication systems require increasingly more sophisticated management strategies to be adopted in order to guarantee adequate levels of performance and reliability. The centralized paradigm adopted by the SNMP is appropriate in several network management applications, but the quick expansion of networks has posed the problem of its scalability, as well as for any other centralized model. Mobile agents represent a challenging approach to provide advanced network management functionalities, due to the possibility to easily implement a decentralized and active monitoring of the system. In this paper we discuss how to take advantage of this technology and identify some reference scenario where mobile agents represent a very promising approach. We also describe a prototype implementation based on our mobile agent platform called MAP and show how it is possible to take advantages from using the features it provides.

Security and Cloud Computing: InterCloud Identity Management Infrastructure

Cloud Computing is becoming one of the most important topics in the IT world. Several challenges are being raised from the adoption of this computational paradigm including security, privacy, and federation. This paper aims to introduce new concepts in cloud computing and security, focusing on heterogeneous and federated scenarios. We present a reference architecture able to address the Identity Management (IdM) problem in the InterCloud context and show how it can be successfully applied to manage the authentication needed among clouds for the federation establishment.

MAP: design and implementation of a mobile agents' platform

Abstract The recent development of telecommunication networks has contributed to the success of applications such as information retrieval and electronic commerce, as well as all the services that take advantage of communication in distributed systems. In this area, the emerging technology of mobile agents aroused considerable interest. Mobile agents are applications that can move through the network for carrying out a given task on behalf of the user. In this work we present a platform called MAP (Mobile Agents Platform) for the development and the management of mobile agents. The language used both for developing the platform and for carrying out the agents is Java. The platform gives the user all the basic tools needed for creating some applications based on the use of agents. It enables us to create, run, suspend, resume, deactivate, reactivate local agents, to stop their execution, to make them communicate each other and migrate.

Three-Phase Cross-Cloud Federation Model: The Cloud SSO Authentication

Cloud federation aims to cost-effective assets and resources optimization among heterogeneous environments where clouds can cooperate together with the goal of obtaining unbounded computation resources, hence new business opportunities. This paper describes an architecture for the federation establishment, where clouds that need external resources ask to federated clouds the renting of extra physical resources. Our architecture introduces a new module named Cross-Cloud Federation Manager including three agents (Discovery, Match-making and Authentication). In this work, we specifically focus on the authentication agent, which is responsible for a secure federation. To address such problem we propose a technical solution based on the IdP/SP model along with the SAML technology.

An SLA-based Broker for Cloud Infrastructures

The breakthrough of Cloud comes from its service oriented perspective where everything, including the infrastructure, is provided “as a service”. This model is really attractive and convenient for both providers and consumers, as a consequence the Cloud paradigm is quickly growing and widely spreading, also in non commercial contexts. In such a scenario, we propose to incorporate some elements of volunteer computing into the Cloud paradigm through the Cloud@Home solution, involving into the mix nodes and devices provided by potentially any owners or administrators, disclosing high computational resources to contributors and also allowing to maximize their utilization. This paper presents and discusses the first step towards Cloud@Home: providing quality of service and service level agreement facilities on top of unreliable, intermittent Cloud providers. Some of the main issues and challenges of Cloud@Home, such as the monitoring, management and brokering of resources according to service level requirements are addressed through the design of a framework core architecture. All the tasks committed to the architecture’s modules and components, as well as the most relevant component interactions, are identified and discussed from both the structural and the behavioural viewpoints. Some encouraging experiments on an early implementation prototype deployed in a real testing environment are also documented in the paper.

Optimal software rejuvenation for tolerating soft failures

Abstract In recent studies, the phenomenon of software “aging” has come to light which causes performance of a software to degrade with time. Software rejuvenation is a fault tolerance technique which counteracts aging. In this paper, we address the problem of determining the optimal time to rejuvenate a server type software which experiences “soft failures” (witnessed in telecommunication systems) because of aging. The service rate of the software gradually decreases with time and settles to a very low value. Since the performability in this state is unacceptable, it is necessary to “renew” the software to its peak performance level. We develop Markov decision models for such a system for two different queuing policies. For each policy, we define the look-ahead- n cost functions and prove results on the convergence of these functions to the optimal minimal cost function. We also prove simple rules to determine optimal times to rejuvenate for a realistic cost criterion. Finally, the results are illustrated numerically and the effectiveness of the MDP model is compared with that of the simple rules.

Workload-Based Software Rejuvenation in Cloud Systems

Cloud computing is a promising paradigm able to rationalize the use of hardware resources by means of virtualization. Virtualization allows to instantiate one or more virtual machines (VMs) on top of a single physical machine managed by a virtual machine monitor (VMM). Similarly to any other software, a VMM experiences aging and failures. Software rejuvenation is a proactive fault management technique that involves terminating an application, cleaning up the system internal state, and restarting it to prevent the occurrence of future failures. In this work, we propose a technique to model and evaluate the VMM aging process and to investigate the optimal rejuvenation policy that maximizes the VMM availability under variable workload conditions. Starting from dynamic reliability theory and adopting symbolic algebraic techniques, we investigate and compare existing time-based VMM rejuvenation policies. We also propose a time-based policy that adapts the rejuvenation timer to the VMM workload condition improving the system availability. The effectiveness of the proposed modeling technique is demonstrated through a numerical example based on a case study taken from the literature.