In this paper, we address the problem of re-establishing the network connectivity in post-disaster scenarios, where the original wireless infrastructure has been partitioned into multiple network fragments (called islands), operating on different frequencies. To this purpose, we propose the utilization of swarms of dedicated repairing units, called Stem-Nodes (SNs). SNs are provided with Cognitive Radio (CR) and self-positioning capabilities, in order to offer maximum reconfigurability in terms of mobility and wireless technologies supported. Moreover, swarms of SNs can self-organize into STEM-Mesh structure, that works as a dynamic backbone to connect heterogeneous islands using different technologies (e.g. Wi-Fi, Wi-MAX, etc). In this paper, we present three contributions pertaining to STEM-Mesh: (i) we describe a distributed motion control scheme (based on virtual springs approach) that enables SNs to self-organize into dynamic STEM-Mesh structures, (ii) we introduce a discovery scheme, through which SNs can explore the scenario in both spatial and frequency domains, and possibly connect the islands to the STEM-Mesh backbone and (iii) we validate the correctness of the proposed scheme, by verifying the optimal placements of the SNs composing the STEM-Mesh on a simplified scenario (e.g. chain topology). Finally, we evaluate through Omnet++ simulations the ability of STEM-Mesh to maximally re-establish connectivity on partitioned network scenarios.

In this paper we argue that the set of wireless, mobile devices (e.g., portable telephones, tablet PCs, GPS navigators, media players) commonly used by human users enables the construction of what we term a “digital ecosystem”, i.e., an ecosystem constructed out of so-called “digital organisms” (see below), that can foster the development of novel distributed services. In this context, a human user equipped with his/her own mobile devices, can be though of as a “digital organism” (DO), a subsystem characterized by a set of peculiar features and resources it can offer to the rest of the ecosystem for use from its peer DOs. The internal organization of the DO must address issues of management of its own resources, including power consumption. Inside the DO and among DOs, peer-to-peer interaction mechanisms can be conveniently deployed to favor resource sharing and data dissemination. Throughout this paper, we show that most of the solutions and technologies needed to construct a digital ecosystem are already available. What is still missing is a framework (i.e., mechanisms, protocols, services) that can support effectively the integration and cooperation of these technologies. In addition, in the following we show that that framework can be implemented as a middleware subsystem that enables novel and ubiquitous forms of computation and communication. Finally, in order to illustrate the effectiveness of our approach, we introduce some experimental results we have obtained from preliminary implementations of (parts of) that subsystem.

The success of Cloud computing, where computing power is treated as a utility, has resulted in the creation of many large data centers that are very expensive to build and operate. In particular, the energy bill accounts for a significant fraction of the total operation costs. For this reason a significant attention is being devoted to energy conservation techniques, for example by taking advantage of the built-in power saving features of modern hardware. Cloud computing offers novel opportunities for achieving energy savings: Cloud systems rely on virtualization techniques to allocate computing resources on demand, and modern Virtual Machine (VM) monitors allow live migration of running VMs. Thus, energy conservation can be achieved through server consolidation, moving VM instances away from lightly loaded computing nodes so that they become empty and can be switched to low-power mode. In this paper we present V-MAN, a fully decentralized algorithm for consolidating VMs in large Cloud datacenters. V-MAN can operate on any arbitrary initial allocation of VMs on the Cloud, iteratively producing new allocations that quickly converge towards the one maximizing the number of idle hosts. V-MAN uses a simple gossip protocol to achieve efficiency, scalability and robustness to failures. Simulation experiments indicate that, starting from a random allocation, V-MAN produces an almost-optimal VM placement in just a few rounds; the protocol is intrinsically robust and can cope with computing nodes being added to or removed from the Cloud.

In this paper we discuss the design and experimental evaluation of a middleware architecture that enables Service Level Agreement (SLA)-driven dynamic configuration, management and optimization of cloud resources and services. This architecture has been designed in order to respond effectively to the Quality of Service (QoS) requirements of the cloud customer applications. Typically, an application can be hosted in an execution platform constructed out of (real and virtual) cloud resources. In this context, the application QoS requirements can be specified in a SLA that binds the application to its hosting platform. Our architecture incorporates a load balancer that distributes the computational load across the platform resources, and monitors the QoS the platform delivers. If this deviates from that specified in the SLA, so as to violate it, the platform is reconfigured dynamically in order to incorporate additional resources from the cloud. In contrast, if the SLA is honored and platform resources result unused, platform reconfiguration occurs to release those unused resources.

We describe a cross-layer architecture we are developing in order to offer mobility support to wireless devices executing multimedia applications which require seamless communications. This architecture is based on the use of pairs of proxies, which enable the adaptive and concurrent use of different network interfaces during the communications. A cloud computing environment is used as the infrastructure to set up (and release) dynamically the proxies on the server-side, in accordance with the pay-as-you-go principle of cloud based services.

In this paper, we discuss the design, implementation, and experimental evaluation of a middleware architecture for enabling service level agreement (SLA)-driven clustering of QoS-aware application servers. Our middleware architecture supports application server technologies with dynamic resource management: application servers can dynamically change the amount of clustered resources assigned to hosted applications on-demand so as to meet application-level quality of service (QoS) requirements. These requirements can include timeliness, availability, and high throughput and are specified in SLAs. A prototype of our architecture has been implemented using the open-source J2EE application server JBoss. The evaluation of this prototype shows that our approach makes possible JBoss' resource usage optimization and allows JBoss to effectively meet the QoS requirements of the applications it hosts, i.e., to honor the SLAs of those applications

The availability of smart portable telephones, equipped with cameras and microphones, enables portable phone users to capture fragments of audio and video, taken directly from their daily lives. Thus, a new generation of mobile blogs, termed “moBlogs”, is emerging. Conceptually similar to textual Web logs, moBlogs collect text, images, audio and video, captured by mobile devices, and make them available on-line. In addition, the availability of different connectivity options on board the same portable phone (from Bluetooth, through 2.5/3G to WLAN) can improve the ability of the phone users to browse and update the moBlogs of interest to them. Within this scenario, in order to simplify the development of mobile applications for smart portable phones, and to enhance their reusability, it is necessary to provide those applications with appropriate communication support that shields them from the heterogeneities of the multiple connectivity options mentioned above. In this sense, the paper presents an application-transparent middleware designed and developed to provide mobile applications with end-to-end, Always Best Connected (ABC), and seamless connectivity, even in case of handoff events and network interface reconfigurations. 1.

This paper introduces an experimental evaluation of a set of middleware services we have developed in order to enable application server technology to meet such quality of service (QoS) application requirements as service availability, timeliness and throughput. These services, developed in the context of the EU funded project TAPAS, have been integrated in the open source JBoss application server, and are publicly available

In this paper we discuss the use of algorithms and techniques, currently deployed in peer-to-peer (P2P) systems, in the design of content distribution internetworks (CDIs). Specifically, we propose a CDI design approach that addresses issues of request routing, content delivery, and replication, based on P2P techniques.

The paper presents the design of a software infrastructure that can support negotiation and competition among buyers and sellers of goods (auctioning) over the Internet. The goals of data integrity, responsiveness, and scalability have been achieved by replicating the auction service across a number of auction servers.

We propose a communication software architecture designed to support distributed multimedia applications. We show that this architecture is scalable, and can provide high availability of the communication services.>

Rajdoot is a remote procedure call (RPC) mechanism with a number of fault tolerance capabilities. A discussion is presented of the reliability-related issues and how these issues have been dealt with in the RPC design. Rajdoot supports exactly-once semantics with call nesting capability, and incorporates effective measures for orphan detection and killing. Performance figures show that the reliability measures of Rajdoot impose little overhead.>

Abstract This paper describes an implementation of a software interface designed for use from within UNIX UNIX is a trademark of A T & T Bell Laboratories. application programs for network communications. This interface provides the abstraction of possibly very large datagrams, supports ‘scatter‐gather’ facilities, and maintains standard network addresses consisting of (host number; port number) pairs. This interface has been provided on different data communication facilities, allowing uniform program access to those facilities. The particular implementation developed for a local area network is described, and performance results obtained are examined and compared with those obtained from a conventional datagram interface to that network. The results obtained confirm that the abstraction of very large datagrams enables the construction of an efficient mechanism for process‐to‐process communications over the network that is not only more convenient, but also has significant performance advantages over the use of conventional (small) datagrams.

We propose an interface for use from within UNIX1 user programs for communicating over multiple and varied local and wide area networks. This interface aids the design of a distributed application program by hiding the actual communications protocols used over each network, and providing instead simple primitives for sending and receiving (possibly large) datagrams, using a simple standardized network addressing scheme based on apair.

In this correspondence we describe the design of a reliable Remote Procedure Call mechanism intended for use in local area networks. Starting from the hardware level that provides primitive facilities for data transmission, we describe how such a mechanism can be constructed. We discuss various design issues involved, including the choice of a message passing system over which the remote call mechanism is to be constructed and the treatment of various abnormal situations such as lost messages and node crashes. We also investigate what the reliability requirements of the Remote Procedure Call mechanism should be with respect to both the application programs using it and the message passing system on which it itself is based.