Panayotis Fouliras

A novel reputation-based model for e-commerce

Reputation systems are very important in e-markets, where they help buyers to decide whether to purchase a product. Since a higher reputation often represents higher profit, malicious users may try to deceive them to increase their reputation. This may be aggravated through fear of retaliation to bad ratings or collusion of multiple users so that they can perform a fraud of high value before being denounced by their victims. In this paper we provide a new reputation management system (RMS) which prevents retaliation and minimizes fake ratings due to collusion. Furthermore, it combines the price and the sales track record of the seller with the charges he has already paid to the system. In this way, it becomes too expensive both in terms of time and money for the malicious users who may collude to launch an organized attack discrediting an e-commerce platform. We test our proposals with several simulation scenarios, verifying the validity of our claims.

The impact of environmental practices on firms’ efficiency: the case of ICT-producing sectors

The aim of this paper is to shed light on the debate concerning the impact of environmental practices on firms’ efficiency. It focuses on two of the most representative sectors of information and communication technologies’ industry, i.e. computer hardware and telecommunications equipment. The Data Envelopment Analysis (DEA) method was chosen to measure firm-level efficiency, since we are interested in the relative evaluation of a firm with respect to all other firms in a given set. The methodology is based on a three-stage approach: (1) construct an appropriate efficiency ratio, (2) divide the sampled companies into two discrete categories, i.e. the companies with more restrictive environmental practices (adherence to specific standards) and those with less restrictive practices (adoption of a general framework), and (3) calculate DEA efficiency scores. According to our findings, ICT companies which implement strict environmental practices are not necessarily more efficient than their rivals. Consequently, except for the case of compulsory regulations, ICT companies should consider all the possibilities and implement the practices best suited to their needs.

LEMP: Lightweight Efficient Multicast Protocol for video on demand

In this paper, we propose a new scalable application-layer protocol, specifically designed for data streaming applications with large client sets. This is based upon a control hierarchy of successive levels for the clients, has minimal overhead with constant number of messages per client, and is robust to client and network failures, making it suitable for wireless environments. The video server bandwidth utilization is also significantly reduced. We present an analysis and simulation results, showing that LEMP is near optimum in terms of performance.

Modeling and managing virtual network environments

While the virtualization concept and its underlying technologies have been adopted in the computer networks field, as in many other Information Technology areas, a generic model of network virtualization environments (NVEs) has not, yet, been proposed. This lack of conceptual impression imposes limitations on the representation and management of these environments. In this paper we propose a new modular and extensible conceptual model, based on Distributed Management Task Forces Common Information Model (DMTF CIM), which can be applied to most scenarios of NVE architectures. We, also, present a test case where the model is extended to include Statistical Process Control methods for guaranteed network performance delivery. In this example, an NVE spans different virtual server nodes, which provide its required resources, and this architecture is modeled and managed resulting in a mechanism to assess and control the overall resources consumption.

Web services and multimedia in m‐business applications: Opportunities and concerns

Web services refer to a specific set of technologies used to implement a Service Oriented Architecture. Thanks to maturing Web‐services standards, and to new mobile devices and application solutions, progress is being made in presenting similar Web‐services offerings in both mobile and fixed networks. To bring that architecture and the solutions it will support to the world of mobility is indeed a significant issue in m‐business applications, because mobile Web services present various advantages: Reduction of the overall cost of development (by reusing existing system components), faster time to market introduction of products (provided by applications’ rapid development and deployment) and remarkable possibilities to emerge new applications with increased functionalities. In addition, the new and forthcoming mobile networks, with native IP connection and high speed transmission capability, allow the development of a variety of modern multimedia services. Multimedia Messaging Services (capable to mix the media types in order to enable more intuitive messaging operation), and Instant Messaging and Presence Services (dedicated for presence, instant messaging, and distribution and sharing of multimedia content in groups of users), provide suitable underlying capabilities to support location‐based and context‐sensitive multimedia services. In this paper we will present the current approaches regarding architectural, functional and security features that allow enterprises to enjoy the benefits of traditional Web services in the mobile multimedia domain.

Statistics-driven datacenter resources provisioning

The virtualization concept along with its underlying technologies has been warmly adopted in many fields of computer science. In modern datacenters, the convergence of communications and computing to a common design and operational entity has proved an inevitable reality, introducing virtual servers as active network elements thus increasing the infrastructure complexity. Effective resource management in such architectures is crucial, impacting both service delivery and the resulting infrastructure operating costs. We propose a novel approach, based on Statistical Process Control (SPC), for the dynamic resource provisioning of datacenter virtualized resources. Our work provides an integrated, platform-independent and technology-neutral, framework consisting of a Common Information Model (CIM) based resource controller which allows for the on-line, adaptive, management of a virtual machines CPU allocation. The controller can be extended to manage other types of hypervisor-provisioned resources. We provide a successful proof-of-concept of our work, deploying the controller on an IBM pSeries UNIX system running a core banking environment software with actual business data. Given the platform agnostic description of the controller and the managed environment it is, thus, possible to easily provide different operating system and hardware platform ports.

A statistical approach to virtual server resource management

Resource management is of key importance in a wide array of computer and network environments. Failure to effectively allocate resources necessary for smooth infrastructure operation may result in impediments in successful service provisioning. This is especially prominent in environments whose workloads present fluctuating resource demand, such as in Cloud‐based infrastructures. The mathematical science of statistics offers an extensive theoretical and practical toolbox that can be of potential use in tackling such problems in the information technology domain. We propose a novel approach to resource management of virtualized data center components. We have worked toward creating a mechanism that allows for dynamic resource allocation, adapting to the changing demand patterns. Our system incorporates a resource controller, based on Statistical Process Control, which permits the online management of a virtual machines processor and memory capacity through real‐time analysis of its observed performance. We successfully demonstrate our approach, with real data, on an architecture running the core banking environment of a financial institution. The controller successfully manages the resource allocation of the virtual machine and stabilizes its performance while business workloads are being processed. Our approach can be extended to realize different workload models and to manage other types of hypervisor provisioned resources.

Conceptualization of Game Based Approaches for Learning and Training on Cyber Security

Utilizing game based approaches for learning and training on cyber security is a way to foster innovative methods and effectively train learners in highly-motivating settings. In this work, we investigate related works on such approaches. Our study reveals only a limited set of works focusing on diverse target groups and methodologies and a lack of conceptual analysis and design standards. To this end, we analyse the structure of cyber security learning and training approaches that utilize gamification and game based learning notions; we decompose these approaches into their respective elements; we define their relations; and we construct a concept map of pedagogical and technological elements of game based learning and training approaches on cyber security.

Conceptual analysis of cyber security education based on live competitions

Live competitions, i.e. Capture the Flag, provide noteworthy experiences for the participants while offering both hands-on practice and entertainment. Aiming at performing a conceptual analysis as a basis for improving their pedagogical utilization, we investigate a number of live competition paradigms and analyse their structure by decomposing them into their respective elements and defining their relations. Moreover, we record the possible obstacles related to the pedagogical utilization of live competitions and group them into distinct categories. As a result, we construct a concept map of the technological and pedagogical characteristics of live competitions. Based on the proposed concept map and the recorded obstacles, we present a comparative evaluation scheme that we employ on three live competition approaches from the literature in order to reveal their value with respect to the educational impact. Finally, we discuss the results of our study and suggest directions for its utilization in the phases of analysis, feasibility and assessment towards developing of new live competition approaches for educational purposes. The adopted assumptions can bind the design of new efforts in cyber security education domain such as gamification and game based learning approaches that need to rely on sound learning theories, e.g. cognitive and experiential learning.

Host-Based Virtual Networks Management in Cloud Datacenters

Infrastructure management is of key importance in a wide array of computer and network environments. The use of virtualization in cloud datacenters has driven the communications and computing convergence to a common operational entity. Failure to effectively manage the involved infrastructure results as impediments in provisioning a successful service. Information models facilitate the infrastructure management and current solutions can be effectively applied in most datacenter scenarios, apart from cases where the networking architecture relies heavily on systems virtualization. In this paper we propose an information model for managing virtual network architectures, where hypervisors and computing server resources are deployed as the basis of the networking layer. We provide a successful proof of concept by managing a virtual machine-based network infrastructure acting as an IP routing platform using statistical methods. Our proposal enables a dynamic reconfiguration of allocated infrastructure resources adapting, in real-time, to variations in the imposed workload.