Francesco Lo Presti - Profile on Academia.edu (original) (raw)

Papers by Francesco Lo Presti

— In this paper, we study the problem of resource allocation and control for a network node with ... more — In this paper, we study the problem of resource allocation and control for a network node with regulated traffic. Both guaranteed lossless service and statistical service with small loss probability are considered. We investigate the relationship between source characteristics and the buffer/bandwidth tradeoff under both services. Our contributions are the following. For guaranteed lossless service, we find that the optimal resource allocation scheme suggests that sources sharing a network node with finite bandwidth and buffer space divide into groups according to time scales defined by their leaky-bucket parameters. This time-scale separation determines the manner by which the buffer and bandwidth resources at the network node are shared among the sources. For statistical service with a small loss probability, we present a new approach for estimating the loss probability in a shared buffer multiplexor using the “extremal ” ON–OFF, periodic sources. Under this approach, the optima...

The Service-Oriented Architecture (SOA) paradigm supports a collaborative business model, where b... more The Service-Oriented Architecture (SOA) paradigm supports a collaborative business model, where business applications are built from independently developed services, and services and applications build up complex dependencies. Guaranteeing high dependability levels in such complex environment is a key factor for the success of this model. In this chapter we discuss issues concerning the design of such software sys-tems, evidencing the limits of the proposed approaches, and suggesting directions for advancements in this field. Moreover, we also discuss issues concerning the case of self-adaptive SOA systems, whose goal is to self-configure themselves, to cope with changes in the operating conditions and to meet the required dependability with a minimum of resources.

Abstract. In the service computing paradigm, a service broker can build new applications by compo... more Abstract. In the service computing paradigm, a service broker can build new applications by composing network-accessible services offered by loosely coupled independent providers. In this paper, we address the admission control problem for a a service broker which offers to prospective users a composite service with a range of different Quality of Service (QoS) classes. We formulate the problem as a Markov Decision Process (MDP) problem with the goal of maximizing the broker revenue while guaranteeing non-functional QoS requirements to its already admitted users. To assess the effectiveness of the MDP-based admission control, we present experimental results where we compare the optimal decisions obtained by the analytical solution of the MDP with other policies. 1

We consider several Software as a Service (SaaS) providers that offer applications using the Clou... more We consider several Software as a Service (SaaS) providers that offer applications using the Cloud facilities provided by an Infrastructure as a Service (IaaS) provider which adopts a payper-use scheme similar to the Amazon EC2 service, comprising flat, on demand, and spot virtual machine instances. For this scenario, we study the virtual machine provisioning and spot pricing strategies. We consider a two stage provisioning scheme. In the first stage, the SaaS providers determine the optimal number of required flat and on demand instances. Then, in the second stage, the IaaS provider sells its unused capacity as spot instances for which the SaaS providers compete by submitting a bid. We study two different IaaS provider pricing strategies: the first assumes the IaaS provider sets a unique price; in the second, instead, the IaaS provider can set different prices for different users. We model the resulting problem as a Stackelberg game. For each pricing scheme, we provide proof of the...

Data Stream Processing (DSP) applications should be capable to efficiently process high-velocity ... more Data Stream Processing (DSP) applications should be capable to efficiently process high-velocity continuous data streams by elastically scaling the parallelism degree of their operators so to deal with high variability in the workload. Moreover, to efficiently use computing resources, modern DSP frameworks should seamlessly support infrastructure elasticity, which allows to exploit resources available on-demand in geo-distributed Cloud and Fog systems. In this paper we propose E2DF, a framework to autonomously control the multi-level elasticity of DSP applications and the underlying computing infrastructure. E2DF revolves around a hierarchical approach, with two control layers that work at different granularity and time scale. At the lower level, fully decentralized Operator and Region managers control the reconfiguration of distributed DSP operators and resources. At the higher level, centralized managers oversee the overall application and infrastructure adaptation. We have integr...

Algorithmic Aspects of Cloud Computing

The fast increasing presence of Internet-of-Things and fog computing resources exposes new challe... more The fast increasing presence of Internet-of-Things and fog computing resources exposes new challenges due to heterogeneity and non-negligible network delays among resources as well as the dynamism of operating conditions. Such a variable computing environment leads the applications to adopt an elastic and decentralized execution. To simplify the application deployment and run-time management, containers are widely used nowadays. The deployment of a container-based application over a geo-distributed computing infrastructure is a key task that has a significant impact on the application non-functional requirements (e.g., performance, security, cost). In this survey, we first develop a taxonomy based on the goals, the scope, the actions, and the methodologies considered to adapt at run-time the application deployment. Then, we use it to classify some of the existing research results. Finally, we identify some open challenges that arise for the application deployment in the fog. In literature, we can find many different approaches for adapting the containers deployment, each tailored for optimizing a specific objective, such as the application response time, its deployment cost, or the efficient utilization of the available computing resources. However, although several solutions for deploying containers exist, those explicitly considering the distinctive features of fog computing are at the early stages: indeed, existing solutions scale containers without considering their placement, or do not consider the heterogeneity, the geographic distribution, and mobility of fog resources.

Proceedings of the 13th ACM International Conference on Distributed and Event-based Systems

Algorithms

The capability of efficiently processing the data streams emitted by nowadays ubiquitous sensing ... more The capability of efficiently processing the data streams emitted by nowadays ubiquitous sensing devices enables the development of new intelligent services. Data Stream Processing (DSP) applications allow for processing huge volumes of data in near real-time. To keep up with the high volume and velocity of data, these applications can elastically scale their execution on multiple computing resources to process the incoming data flow in parallel. Being that data sources and consumers are usually located at the network edges, nowadays the presence of geo-distributed computing resources represents an attractive environment for DSP. However, controlling the applications and the processing infrastructure in such wide-area environments represents a significant challenge. In this paper, we present a hierarchical solution for the autonomous control of elastic DSP applications and infrastructures. It consists of a two-layered hierarchical solution, where centralized components coordinate su...

Proceedings International Parallel and Distributed Processing Symposium, 2003

the following article is about the network Quality of Service issues, which is a set of technolog... more the following article is about the network Quality of Service issues, which is a set of technologies that enable to users obtain from the network predicted level of services basing on particular rules e.g. throughput, delay and jitter. An Investigation and comparison of QoS mechanisms, focusing on the Internet Protocols has been done here, to analyze and compare existing solutions. Beginning from wired environment, where there are already wellknown and well-designed QoS solutions like IntServ and DiffServ, we focus on the wireless communications which demands additional sometimes sophisticated protocols to be able to effectively handle mobility in communications..

Admission control policies for a multi-class QoS-aware service oriented architecture

ACM SIGMETRICS Performance Evaluation Review, 2012

In the service computing paradigm, a service broker can build new applications by composing netwo... more In the service computing paradigm, a service broker can build new applications by composing network-accessible services offered by loosely coupled independent providers. In this paper, we address the problem of providing a service broker, which offers to prospective users a composite service with a range of different Quality of Service (QoS) classes, with a forward-looking admission control policy based on Markov Decision Processes (MDP). This mechanism allows the broker to decide whether to accept or reject a new potential user in such a way to maximize its gain while guaranteeing non-functional QoS requirements to its already admitted users. We model the broker using a continuous-time MDP and consider various techniques suitable to solve both infinite-horizon and finitehorizon MDPs. To assess the effectiveness of the MDP-based admission control for the service broker, we present simulation results where we compare the optimal decisions obtained by the analytical solution of the MDP with other admission control policies. To deal with large problem instances, we also propose a heuristic policy for the MDP solution.

7th Joint Meeting of the European Software Engineering Conference and the Acm Sigsoft Symposium on the Foundations of Software Engineering, 2009

Runtime adaptation is recognized as a viable way for a serviceoriented system to meet QoS require... more Runtime adaptation is recognized as a viable way for a serviceoriented system to meet QoS requirements in its volatile operating environment. In this paper we propose a methodology to drive the adaptation of such a system, that integrates within a unified framework different adaptation mechanisms, to achieve a greater flexibility in facing different operating environments and the possibly conflicting QoS requirements of several concurrent users. To determine the most suitable adaptation action(s), the methodology is based on the formulation and solution of a linear programming problem, which is derived from a behavioral model of the system updated at runtime by a monitoring activity. Numerical experiments show the effectiveness of our approach. Besides the methodology, we also present a prototype tool that implements it.

The Content Delivery Networks (CDN) paradigm is based on the idea to transparently move third-par... more The Content Delivery Networks (CDN) paradigm is based on the idea to transparently move third-party content closer to the users. More specifically, content is replicated on CDN servers which are located close to the final users, and user requests are redirected to the “best ” replica (e.g. the closest) in a transparent way, so that users perceive a better content access service. In this paper we address the problem of dynamic replica placement. Being dynamic, our solutions adaptively se-lect the number of replicas for each content and the repli-cas positions to account for traffic requests dynamics. The schemes we propose are designed to minimize the overall cost paid by the CDN provider (for replicas placement, re-moval, and maintenance) without degrading the quality of the users perceived access service. The contributions of the paper are twofold. First we introduce a centralized and distributed scheme for replica placement in a dynamic traffic scenario. Then, by means of a simula...

Autonomous Control for a Reliable Internet of Services, 2018

Traditional networks are transformed to enable full integration of heterogeneous hardware and sof... more Traditional networks are transformed to enable full integration of heterogeneous hardware and software functions, that are configured at runtime, with minimal time to market, and are provided to their end users on "as a service" principle. Therefore, a countless number of possibilities for further innovation and exploitation opens up. Network Function Virtualization (NFV) and Software-Defined Networking (SDN) are two key enablers for such a new flexible, scalable, and service-oriented network architecture. This chapter provides an overview of QoS-aware strategies that can be used over the levels of the network abstraction aiming to fully exploit the new network opportunities. Specifically, we present three use cases of integrating SDN and NFV with QoS-aware service composition, ranging from the energy efficient placement of virtual network functions inside modern data centers, to the deployment of data stream processing applications using SDN to control the network paths, to exploiting SDN for context-aware service compositions.

Service selection has been widely investigated as an effective adaptation mechanism that allows a... more Service selection has been widely investigated as an effective adaptation mechanism that allows a service broker, offering a composite service, to bind each task of the abstract composition to a corresponding implementation, selecting it from a set of candidates. The selection aims typically to fulfill the Quality of Service (QoS) requirements of the composite service, considering several QoS parameters in the decision. We compare the performance of two representative examples of the perrequest and per-flow approaches that address the service selection issue at a different granularity level. We present experimental results obtained with a prototype implementation of a service broker. Our results show the ability of the per-flow approach in sustaining an increasing traffic of requests, while the per-request approach appears more suitable to offer a finer customizable service selection in a lightly loaded system.

An MDP-based admission control for a QoS-aware service-oriented system

In this paper, we address the problem of providing a service broker, which offers to prospective ... more In this paper, we address the problem of providing a service broker, which offers to prospective users a composite service with a range of different Quality of Service (QoS) classes, with a forward-looking admission control policy based on Markov Decision Processes (MDPs).

Joint congestion control: routing and media access control optimization via dual decomposition for ad hoc wireless networks

ABSTRACT In this paper we present a model for the joint congestion control, routing and MAC link ... more ABSTRACT In this paper we present a model for the joint congestion control, routing and MAC link access for ad hoc wireless networks. We formulate the problem as a utility maximization problem with routing and link access constraints. For the solution we exploit the separable structure of the problem via dual decomposition and the sub-gradient algorithm. The resulting algorithm directly translates into a distributed cross-layer scheme for joint congestion control, routing and link scheduling of the wireless links which revolves around link layer pricing. The convex problem formulation and the use of the sub-gradient algorithm ensures that the solution converges within an interval of the optimal value. We illustrate the algorithm behavior through examples.

The use of end-to-end multicast traffic measurements has been recently proposed as a means to inf... more The use of end-to-end multicast traffic measurements has been recently proposed as a means to infer network internal characteristics as packet link loss rate and delay. In this paper, we propose an algorithm that infers the multicast tree topology based on these end-to-end measurements. Differently from previous approaches which make only partial use of the available information, this algorithm adaptively combines different performance measures to reconstruct the topology. We establish its consistency and evaluate its accuracy through simulation. We show that in general it requires many fewer probes to correctly identify the topology than other methods.

Modeling, Analysis & …, 2009

All runtime management decisions in computer and information systems require immediate detection ... more All runtime management decisions in computer and information systems require immediate detection of relevant changes in the state of their resources. This is accomplished by continuously monitoring the performance/utilization of key system resources and by using appropriate statistical tests to detect the occurance of significant state changes. Unfortunately, the complexity of today systems and applications and the unpredictability of user request patterns result in highly variable and non stationary time series which are difficult to analyze. As a consequence, present solutions for detecting state changes at runtime are affected by excessive time delays or false positives. We propose a novel "agile" runtime detector that solves the delay vs. false positive tradeoff: it is able to detect the relevant state changes as fast as the best reactive models with the lowest percentages of false positives. All evaluations carried out for a large set of scenarios confirm the efficacy and robustness of the proposed model.

In the service computing paradigm, a service broker can build new applications by composing netwo... more In the service computing paradigm, a service broker can build new applications by composing network-accessible services offered by loosely coupled independent providers. In this paper, we address the admission control problem for a a service broker which offers to prospective users a composite service with a range of different Quality of Service (QoS) classes. We formulate the problem as a Markov Decision Process (MDP) problem with the goal of maximizing the broker revenue while guaranteeing non-functional QoS requirements to its already admitted users. To assess the effectiveness of the MDP-based admission control, we present experimental results where we compare the optimal decisions obtained by the analytical solution of the MDP with other policies.

Statistical inference of internal network loss and topology

The use of inference from end-to-end multicast measurements has recently been proposed to find th... more The use of inference from end-to-end multicast measurements has recently been proposed to find the internal characteristics in a network. Here we describe statistically rigorous methods for inferring link loss rates, and their application to identifying the underlying multicast topology.

Algorithmic Aspects of Cloud Computing

Proceedings of the 13th ACM International Conference on Distributed and Event-based Systems

Algorithms

Proceedings International Parallel and Distributed Processing Symposium, 2003

Admission control policies for a multi-class QoS-aware service oriented architecture

ACM SIGMETRICS Performance Evaluation Review, 2012

7th Joint Meeting of the European Software Engineering Conference and the Acm Sigsoft Symposium on the Foundations of Software Engineering, 2009

Autonomous Control for a Reliable Internet of Services, 2018

An MDP-based admission control for a QoS-aware service-oriented system

Joint congestion control: routing and media access control optimization via dual decomposition for ad hoc wireless networks

Modeling, Analysis & …, 2009

In the service computing paradigm, a service broker can build new applications by composing netwo... more In the service computing paradigm, a service broker can build new applications by composing network-accessible services offered by loosely coupled independent providers. In this paper, we address the admission control problem for a a service broker which offers to prospective users a composite service with a range of different Quality of Service (QoS) classes. We formulate the problem as a Markov Decision Process (MDP) problem with the goal of maximizing the broker revenue while guaranteeing non-functional QoS requirements to its already admitted users. To assess the effectiveness of the MDP-based admission control, we present experimental results where we compare the optimal decisions obtained by the analytical solution of the MDP with other policies.

Statistical inference of internal network loss and topology