Performance Analysis of Publish/Subscribe Systems

The Desktop Grid offers solutions to overcome several challenges and to answer increasingly needs of scientific computing. Its technology consists mainly in exploiting resources, geographically dispersed, to treat complex applications needing big power of calculation and/or important storage capacity. However, as resources number increases, the need for scalability, self-organisation, dynamic reconfigurations, decentralisation and performance becomes more and more essential. Since such properties are exhibited by P2P systems, the convergence of grid computing and P2P computing seems natural. In this context, this paper evaluates the scalability and performance of P2P tools for discovering and registering services. Three protocols are used for this purpose: Bonjour, Avahi and Free-Pastry. We have studied the behaviour of theses protocols related to two criteria: the elapsed time for registrations services and the needed time to discover new services. Our aim is to analyse these results in order to choose the best protocol we can use in order to create a decentralised middleware for desktop grid

Cloud-based desktop services for thin clients

Cloud computing and ubiquitous network availability have renewed people's interest in the thin client concept. By executing applications in virtual desktops on cloud servers, users can access any application from any location with any device. For this to be a successful alternative to traditional offline applications, however, researchers must overcome important challenges. The thin client protocol must display audiovisual output fluidly, and the server executing the virtual desktop should have sufficient resources and ideally be close to the user's current location to limit network delay. From a service provider viewpoint, cost reduction is also an important issue

Semantic multimedia remote display for mobile thin clients

Current remote display technologies for mobile thin clients convert practically all types of graphical content into sequences of images rendered by the client. Consequently, important information concerning the content semantics is lost. The present paper goes beyond this bottleneck by developing a semantic multimedia remote display. The principle consists of representing the graphical content as a real-time interactive multimedia scene graph. The underlying architecture features novel components for scene-graph creation and management, as well as for user interactivity handling. The experimental setup considers the Linux X windows system and BiFS/LASeR multimedia scene technologies on the server and client sides, respectively. The implemented solution was benchmarked against currently deployed solutions (VNC and Microsoft-RDP), by considering text editing and WWW browsing applications. The quantitative assessments demonstrate: (1) visual quality expressed by seven objective metrics, e.g., PSNR values between 30 and 42 dB or SSIM values larger than 0.9999; (2) downlink bandwidth gain factors ranging from 2 to 60; (3) real-time user event management expressed by network round-trip time reduction by factors of 4-6 and by uplink bandwidth gain factors from 3 to 10; (4) feasible CPU activity, larger than in the RDP case but reduced by a factor of 1.5 with respect to the VNC-HEXTILE

Virtualization: an old concept in a new approach

Virtualization technology is transforming today’s IT community, offering new possi-bilities to improve the performance and efficiency of IT infrastructure by a dynamic mapping of the PC resources, enabling to run multiple applications and operating systems on a single physical system. Virtualization also offers high availability and error recovery solutions by encapsulating entire systems into single files that can be replicated and restored on any desti-nation machine. This paper brings new elements related to the concept of virtualization, presenting the princi-ples, the new architectures and the advantages of the virtualization. We make also a brief comparison between the PC’s functional structure before and after the virtualization. Finally, we present licensed software to create and run multiple virtual machines on a personal com-puter

Reinventing the university

In view of the discernible trends in Higher Education towards increased numbers, increased diversity and expectations of students, declining resources, increased competition between providers and increasingly irregular patterns of student attendance, there is a need to establish new ways of delivering and supporting teaching and learning. The convergence of different media into a single networked digital domain, and the rapidly expanding accessibility of such media, both driven by market forces, is tempting many HE institutions to develop an online presence. True ‘virtual universities’, i.e., completely online, are still the exception and there are strong reasons why traditional, face‐to‐face, universities should resist the pressure to develop a virtual alter ego. Nevertheless, online delivery and support of teaching and learning offers many potential benefits to students of such institutions, not least of which could be freedom from the constraints of conventional attendance patterns