Giuseppe Di Modica

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.

Expeerience: a JXTA middleware for mobile ad-hoc networks

The combination of personal computing devices and wireless ad-hoc networks allows the concept of mobile ad-hoc information system, consisting of a highly dynamic, decentralized and self-organizing network of autonomous and mobile devices that interact as peers [M. Hannicainen et al. (2002), L. Kleinrock, (2000)]. Here we define a middleware layer, named Expeerience. We have decided to adopt as a basic software framework, an emerging P2P open technology such as JXTA. The second issue we address in this work is the integration of some code mobility support in the developed middleware to allow the distribution and execution of services on peers that originally do not own the service code. This has been introduced in our platform by adding a mobile code service, which enables to download and install new services dynamically only if necessary.

Dynamic SLAs management in service oriented environments

The increasing adoption of service oriented architectures across different administrative domains, forces service providers to use effective mechanisms and strategies of resource management in order for them to be able to guarantee the quality levels their customers demands during service provisioning. Service level agreements (SLA) are the most common mechanism used to establish agreements on the quality of a service (QoS) between a service provider and a service consumer. The WS-Agreement specification, developed by the Open Grid Forum, is a Web Service protocol to establish agreements on the QoS level to be guaranteed in the provision of a service. The committed agreement cannot be modified during service provision and is effective until all activities pertaining to it are finished or until one of the signing party decides to terminate it. In B2B scenarios where several service providers are involved in the composition of a service, and each of them plays both the parts of provider and customer, several one-to-one SLAs need to be signed. In such a rigid context the global QoS of the final service can be strongly affected by any violation on each single SLA. In order to prevent such violations, SLAs need to adapt to any possible needs that might come up during service provision. In this work we focus on the WS-Agreement specification and propose to enhance the flexibility of its approach. We integrate new functionality to the protocol that enable the parties of a WS-Agreement to re-negotiate and modify its terms during the service provision, and show how a typical scenario of service composition can benefit from our proposal.

Resource and service discovery in SOAs: A P2P oriented semantic approach

Resource and service discovery in SOAs: A P2P oriented semantic approach An intense standardization process is favouring the convergence of grids and Service Oriented Architectures (SOAs). One of the benefits of such technological convergence is that grid resources and applications can be virtualized by services and offered through the SOA paradigm. In the broad and interoperable scenarios enabled by the SOA, involving the participation of several grid infrastructures across many administrative domains, service discovery can be a serious issue. In this paper we present a P2P-based infrastructure that leverages semantic technologies to support a scalable and accurate service discovery process. The key concept of the presented idea is the creation of an overlay network organized in several semantic groups of peers, each specialized in answering queries pertaining to specific applicative domains. Groups are formed by clustering together peers offering services that are semantically related. The architecture details of the proposed solution are presented. A system prototype has also been implemented and validated through a case study deployed on the PlanetLab testbed.

A Strategy to Optimize Resource Allocation in Auction-Based Cloud Markets

Current markets of cloud resources are mainly based on a fixed pricing model. In the recent literature several market-based resource allocation models and algorithms have been proposed, showing that dynamic pricing models could result more profitable for both providers and consumers. In this paper we propose a market of resources where the demand and the offer of resources is matched in auction-based sales. Specifically, we looked at this market from the perspective of the provider, who needs a strategy to allocate at best their unused computing capacity. We proposed an adaptive strategy that, suitably customized to the providers business objective, help them to maximize the revenue in the context of procurement auctions. Furthermore, the impact of resource overbooking onto the utilization level of cloud data centers has been analyzed by means of extensive simulations.

Matchmaking semantic security policies in heterogeneous clouds

The adoption of the cloud paradigm to access IT resources and services has posed many security issues which need to be cared of. Security becomes even a much bigger concern when services built on top of many commercial clouds have to interoperate. Among others, the value of the service delivered to end customers is strongly affected by the security of network which providers are able to build in typical SOA contexts. Currently, every provider advertises its own security strategy by means of proprietary policies, which are sometimes ambiguous and very often address the security problem from a non-uniform perspective. Even policies expressed in standardized languages do not appear to fit a dynamic scenario like the SOAs, where services need to be sought and composed on the fly in a way that is compatible with the end-to-end security requirements. We then propose an approach that leverages on the semantic technology to enrich standardized security policies with an ad-hoc content. The semantic annotation of policies enables machine reasoning which is then used for both the discovery and the composition of security-enabled services. In the presented approach the semantic enrichment of policies is enforced by an automatic procedure. We further developed a semantic framework capable of matchmaking in a smart way security capabilities of providers and security requirements of customers, and tested it on a use case scenario. Semantic matchmaking of security policies in cloud environments.Security ontology for modeling security concepts.Automatic semantic annotation of WS-SecurityPolicy policies.

Semantic Security Policy Matching in Service Oriented Architectures

Cloud computing poses several new security andprivacy challenges, mainly related to resource sharing, interoperabilityand dinamicity among different providers. Althoughpolicy specification languages address some of these challenges,many issues still have to be faced with. Policy matching is todayperformed by way of syntactical approaches, which may limitthe selection of suitable services on the one hand, and theflexibility and the dinamicity of the matching process on theother one. In this work we propose a semantic approach that,by means of semantic annotations to WS-Policy documents,allows for an improved matching of security requirementsand capabilities based on their actual meaning. The proposedapproach has been validated through a case study that showshow a pure syntactic-based mechanism of WS-Policy wouldhave failed in matching two actually compatible policies.

Matching the business perspectives of providers and customers in future cloud markets

To date a few, big providers dominate the market of Cloud resources. They provide proprietary solutions through inflexible pricing and SLA schemes. On the research side, the community is working to define specifications and standards on several aspects of the cloud technology. When standards will get mature, interoperability among clouds will be a reality. Customers will be no more locked-up to any proprietary technology and new players will have the chance to enter the market. The competition challenge will be played on the real capability of providers to accommodate customers’ requests in a flexible way and to supply high and differentiated QoS levels. In this market scenario a mechanism must be devised to support the matchmaking between what providers offer and what customers’ applications demand. In this work we propose the definition of a semantic model that helps customers and providers to characterize their demands/offers, and provide semantic tools performing the matchmaking in such a way to maximize both the provider’s profit and the customer’s utility. The proposal has been validated by running tests on a software prototype of the discovery framework.

Dynamically adaptable user interface generation for heterogeneous computing devices

The increasing number of personal computing devices today available for accessing online services and information is making more difficult and time-consuming to develop and maintain several versions of user interfaces for a single application. Moreover, users want to access services they have subscribed, no matter the device they are using, always maintaining their preferences. These issues demand for new software development models, able to easily adapt the application to the client’s execution context, while keeping the application logic separated from its presentation. In this work we present a framework that allows to specify the user’s interaction with the application, in an independent manner with respect to the specific execution’s context, by using an XML-based language. Starting from such a specification, the system will subsequently ”render” the actual user’s application interface on a specific execution environment, adapting it to the end user’s device characteristics.

An infrastructure-less peer-to-peer framework for mobile handheld devices

Mobile handheld devices are becoming more and more widely common among users. Their increasing computing and storage capabilities together with the widespreading of new wireless communication technologies, enable these devices for new and useful applications. The peer-to-peer (P2P) paradigm, which has recently experienced a wide diffusion among internet users, seems to be very well suited to effectively support mobile applications. However, several questions arise when trying to develop such systems: existing solutions do not address all the requirements of these mobile environments. In this paper, we present a framework to develop mobile applications that exploits the P2P paradigm: it is designed to work on Java micro edition (J2ME) enabled mobile devices, interacting each other in an ad hoc fashion. One of the key features is to be interoperable with JXTA, a well-known P2P open platform, by extending the advantages of P2P computing to mobile computing environments. A simple but effective example of application is also provided showing the viability of the designed framework. Copyright