Chrysa A. Papagianni

On the optimal allocation of virtual resources in cloud computing networks

Cloud computing builds upon advances on virtualization and distributed computing to support cost-efficient usage of computing resources, emphasizing on resource scalability and on demand services. Moving away from traditional data-center oriented models, distributed clouds extend over a loosely coupled federated substrate, offering enhanced communication and computational services to target end-users with quality of service (QoS) requirements, as dictated by the future Internet vision. Toward facilitating the efficient realization of such networked computing environments, computing and networking resources need to be jointly treated and optimized. This requires delivery of user-driven sets of virtual resources, dynamically allocated to actual substrate resources within networked clouds, creating the need to revisit resource mapping algorithms and tailor them to a composite virtual resource mapping problem. In this paper, toward providing a unified resource allocation framework for networked clouds, we first formulate the optimal networked cloud mapping problem as a mixed integer programming (MIP) problem, indicating objectives related to cost efficiency of the resource mapping procedure, while abiding by user requests for QoS-aware virtual resources. We subsequently propose a method for the efficient mapping of resource requests onto a shared substrate interconnecting various islands of computing resources, and adopt a heuristic methodology to address the problem. The efficiency of the proposed approach is illustrated in a simulation/emulation environment, that allows for a flexible, structured, and comparative performance evaluation. We conclude by outlining a proof-of-concept realization of our proposed schema, mounted over the European future Internet test-bed FEDERICA, a resource virtualization platform augmented with network and computing facilities.

A Cloud-Oriented Content Delivery Network Paradigm: Modeling and Assessment

Cloud-oriented content delivery networks (CCDNs) constitute a promising alternative to traditional content delivery networks. Exploiting the advantages and principles of the cloud, such as the pay as you go business model and geographical dispersion of resources, CCDN can provide a viable and cost-effective solution for realizing content delivery networks and services. In this paper, a hierarchical framework is proposed and evaluated toward an efficient and scalable solution of content distribution over a multiprovider networked cloud environment, where inter and intra cloud communication resources are simultaneously considered along with traditional cloud computing resources. To efficiently deal with the CCDN deployment problem in this emerging and challenging computing paradigm, the problem is decomposed to graph partitioning and replica placement problems while appropriate cost models are introduced/adapted. Novel approaches on the replica placement problem within the cloud are proposed while the limitations of the physical substrate are taken into consideration. The performance of the proposed hierarchical CCDN framework is assessed via modeling and simulation, while appropriate metrics are defined/adopted associated with and reflecting the interests of the different identified involved key players.

Efficient Resource Mapping Framework over Networked Clouds via Iterated Local Search-Based Request Partitioning

The cloud represents a computing paradigm where shared configurable resources are provided as a service over the Internet. Adding intra- or intercloud communication resources to the resource mix leads to a networked cloud computing environment. Following the cloud infrastructure as a Service paradigm and in order to create a flexible management framework, it is of paramount importance to address efficiently the resource mapping problem within this context. To deal with the inherent complexity and scalability issue of the resource mapping problem across different administrative domains, in this paper a hierarchical framework is described. First, a novel request partitioning approach based on Iterated Local Search is introduced that facilitates the cost-efficient and online splitting of user requests among eligible cloud service providers (CPs) within a networked cloud environment. Following and capitalizing on the outcome of the request partitioning phase, the embedding phase—where the actual mapping of requested virtual to physical resources is performed can be realized through the use of a distributed intracloud resource mapping approach that allows for efficient and balanced allocation of cloud resources. Finally, a thorough evaluation of the proposed overall framework on a simulated networked cloud environment is provided and critically compared against an exact request partitioning solution as well as another common intradomain virtual resource embedding solution.

Mobile crowdsensing as a service

Consumer-centric mobile devices, such as smartphones, are an emerging category of devices at the edge of the Internet. Leveraging volunteers and their mobiles as a (sensing) data collection outlet is known as Mobile Crowd Sensing (MCS) and poses interesting challenges, with particular regard to the management of sensing resource contributors, dealing with their subscription, random and unpredictable join and leave, and node churn.To facilitate and expedite the (commercial) exploitation of this trend, in this paper we propose to adopt a service-oriented approach to cope with MCS application deployment into a sensing Cloud infrastructure, decoupling the MCS application domain from the infrastructure one. To this purpose we provide the building blocks for implementing such a novel take on MCS, which from a Cloud layering perspective can be identified as a platform service, i.e., an MCS as a service (MCSaaS). A prototype implementation that serves as a blueprint and a proof-of-concept of the proposed framework is presented, while an evaluation of the effectiveness of the MCSaaS paradigm has been provided using suitable mobility-related use cases for a validation of the concept, as well as a modeling approach through the adoption of generalized stochastic Petri nets. Emulation of deployment comparing (i) prototype of MCSaaS and (ii) current practices.Modeling of MCSaaS paradigm by Petri nets and evaluation against conventional MCS.Description of architectural elements of the platform and their interactions.MCSaaS platform for mass deployment of MCS apps, and their elastic user base adaptation.Mobile crowdsensing as a service paradigm for MCS apps design and deployment.

Socio-aware virtual network embedding

Network virtualization provides a powerful way to run multiple networks over a shared substrate and has been recognized as a key enabler for overcoming the perceived ossification of the current Internet. This article addresses a specific aspect of network virtualization, virtual network embedding (VNE), which primarily refers to the efficient mapping of virtual resources onto physical ones. Specifically, influenced and inspired by the intersection of recent trends in network virtualization, social network analysis, and service-centric future Internet architectures, in this article the scope of the VNE paradigm is extended by including socio-aware features. Toward this direction, appropriate social-based metrics are introduced, and the conventional VNE objective of minimizing the cost of embedding a request into the substrate under certain physical constraints is extended by considering an additional objective related to the social features of the physical network. An evaluation of the proposed socio-aware VNE paradigm with respect to several aspects and metrics (i.e., accounting, social) is provided and critically compared against conventional VNE approaches. The corresponding results and observations support the vision of paving the way to adopting social-aware virtualized topologies for fostering specific applications within the future Internet paradigm. Finally, the adaptation and prototype of a socio-aware resource mapping approach on a wireless virtualized testbed is summarized, serving as a proof of concept.

Resource discovery and allocation for federated virtualized infrastructures

The European Union Project Networking innovations Over Virtualized Infrastructures (NOVI) set out to design and implement a modular data, control and management plane federation architecture, leading to an integrated experimental prototype mounted on interconnected European Future Internet testbeds. In this paper we present the components of this architecture, responsible for resource discovery and mapping of virtual topologies over a federated multi-domain network virtualization environment. We subsequently introduce a method for the efficient mapping of user requests for virtual networks onto a substrate infrastructure, adopting a semantic-based approach to address the problem. The efficiency of the proposed scheme is evaluated via simulation and critically compared against common non-semantic-based solutions. Networking innovations over virtualized infrastructures-NOVI federation architecture.Resource discovery and allocation over multi-domain virtualized infrastructures.Prototype of a distributed, semantic-based resource discovery and mapping framework.A semantic aware virtual network embedding algorithm.The approach is evaluated via simulation against non-semantic aware solutions.

Particle Swarm Optimization of Antenna Arrays with Efficiency Constraints

Phased array antennas are a viable solution to a number of problems related to radio communications applications. In this work, the multi-objective stochastic MOPSO algorithm is used to optimize the spatial conflguration of a symmetric phased linear array. The deflned optimization goals were the suppression of the radiation pattern sidelobes at a specifled maximum scan angle as well as the minimization of the induced voltages correlation at the receiver front- end in order to maximize diversity performance. Non-linear constraints were enforced on the solution set, related to the multi-antenna system aperture e-ciency and related to the mismatching when the array is scanned. The obtained optimized conflgurations for an array composed of 16 dipoles resulted in reducing the sidelobes up to 2.5dB, when scanned 60 - away from broadside, compared to a linear array with elements spaced ‚=2 apart. Furthermore, the optimized dipole arrays were characterized by a maximum element correlation of 0.12 to 0.43. The performance of obtained conflgurations was shown to be tolerant to feed phase variations that appear in realistic implementations. The arrays were analyzed employing the Method of Moments (MoM).

Optimal design of switched beam antenna arrays using Particle Swarm Optimization

Adaptive antennas techniques are emerging as a promising solution to a number of problems in applications related to mobile communications. This paper presents a method for optimal design of switched beam planar antenna arrays based on the Particle Swarm Optimization (PSO) algorithm. Switched beam antenna arrays are a subset of smart antennas that that can enhance the capacity of a cellular system. PSO is a population based algorithm that exploits a set of potential solutions to the optimization problem, which are determined on the basis of social interactions between independent agents. The synthesis problem addressed is to find spatial and feeding configuration of array elements that conform to certain design constraints enforced on multiple diagrams of differentiated directive gains and values (beam forming). Two different fitness functions were evaluated on this basis; results obtained were correlated to requirements of vertical system integration. The proposed methodology is very flexible allowing the incorporation of additional factors such as coupling characteristics and feeding network constraints.

The Open-Multinet Upper Ontology Towards the Semantic-based Management of Federated Infrastructures

The Internet remains an unfinished work. There are several approaches to enhancing it that have been experimentally validated within federated testbed environments. To best gain scientific knowledge from these studies, reproducibility and automation are needed in all areas of the experiment life cycle. Within the GENI and FIRE context, several architectures and protocols have been developed for this purpose. However, a major open research issue remains, namely the description and discovery of the heterogeneous resources involved. To remedy this, we propose a semantic information model that can be used to allow declarative interoperability, build dependency graphs, validate requests, infer knowledge and conduct complex queries. The requirements for such an information model have been extracted from current international Future Internet research projects and the practicality of the model is being evaluated through initial implementations. The main outcome of this work is the definition of the Open-Multinet Upper Ontology and related sub-ontologies, which can be used to describe and manage federated infrastructures and their resources.

Challenges of an information model for federating virtualized infrastructures

Users of the Future Internet will expect seamless and secure access to virtual resources distributed across multiple domains. These federated platforms are the core of the Future Internet. It is clear that information models, and concrete implementation in data models, are necessary prerequisites for all federative operations, information exchanges, and service support. This position paper describes our approach to the development of an information model for federating virtual infrastructures. Our basic assumption is that semantic resource descriptions with context-awareness, in the form of Semantic Web descriptions, better support services in federated platforms. We use our experiences in the development of two ontologies for computer networks and for network monitoring, NDL and MOMENT, to support and guide our development. The requirements of our envisaged Information and Data models are driven from a concrete use-case, using PlanetLab and FEDERICA as examples of virtualized platforms in a Future Internet federated environment.