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Cloud Computing has been widely adopted as a new paradigm for providing resources because of the advantages it brings to both users and providers. Even if it was firstly targeted at enterprises wishing to reduce their equipment management costs, it has been rapidly recognized as both an enabler for new applications and as a mean to allow enterprises of all sizes at running high demanding applications. Recently, Cloud Providers are trying to attract new applications, such as scientific ones, that today already benefit from distributed environment like Grids. This work presents a way to remove the paradigm mismatch between Cloud and Grid Computing, enabling the use of Cloud-provided resources with well-established Grid-like interfaces, avoiding the need for users to learn new resources access and use models. The proposed approach is validated through the development of a prototype implementation and its integration in a working Grid environment.

Cloud Computing has been receiving great attention in the last few years due to the benefits it provides in terms of flexibility, scalability, virtualization and service provision. Nevertheless, many companies remain reluctant to such a cutting-edge technology due to the serious security issues affecting virtualized environments, especially in critical application scenarios where high safety and dependability levels are required. This work is aimed at discussing and presenting the main security threats for cloud computing infrastructures, as well as proposing a novel architecture in charge of reacting to security attacks in Infrastructure as a Service platforms. The basic idea is to migrate the attacked virtual appliance and to reconfigure the network by means of Software Defined Networking approach. The paper presents the architecture we have in mind and that will be deployed and validated against a real world distributed Air Traffic Control system, for which missing dependability and security targets would result in huge business and human losses.

PlanetLab is a global scale platform for experimentation of new networking applications in a real environment. It consists of several nodes, offered by academic institutions or companies spread all over the world, that can be shared by the networking community for its tests. The main drawback of PlanetLab is its scarce heterogeneity in terms of the access technologies it offers. In this paper we discuss the efforts we made in order to alleviate this problem. We first developed a tool that allowed us to integrate a WiFi testbed controllable by OMF (Orbit Management Framework) [16] in PlanetLab by means of a multi-homed PlanetLab node. OMF is a set of tools that make it easy to automatically execute experiments and collect measurements on a WiFi testbed. The tool we developed allows, more generally, to solve the issues that arises with multi-homed PlanetLab nodes (i.e. PlanetLab nodes having more than a network interface). In order to be able to fully exploit the potential of such PlanetLab nodes, there is the need for the users to add routing rules (e.g. rules to reach a destination through the WiFi interface, instead of the Ethernet interface). Such operation cannot be performed in a PlanetLab environment, as the rules a user adds would also affect other users’ traffic. Therefore it arises the necessity of user-specific routing tables, i.e. routing tables whose rules are only valid for traffic belonging to that user. In this way the user is able to route his traffic through the WiFi interface, and make it traverse the OMF-controllable WiFi testbed, while other users’ traffic continues to get routed through the default primary interface. We also had to support the integration of the OMF facilities (e.g. the OMF controller) into the user environment, which is called slice, in order to allow for the customization of the testbed (e.g. loading a specific disk image on each node) and the automatical execution of experiments. The software we developed to achieve such integration is in the process of being integrated in the code base of PlanetLab, so that anyone is able to integrate its wireless infrastructure in PlanetLab.

We propose a new application-level clustering algorithm capable of building an overlay spanning tree among participants of large multicast sessions, without any specific help from the network routers. This algorithm is based on a unique definition of zones around nodes and an innovative adaptive cluster size distribution. The proposed method finds application in many context where large-scale overlay trees can be usefull: application-level multicasting, peer-to-peer networks and content distribution networks (among other things).

TBCP is a generic Tree Building Control Protocol designed to build overlay spanning trees among participants of a multicast session, without any specific help from the network routers. TBCP therefore falls into the general category of protocols and mechanisms often referred to as Application-Level Multicasting. TBCP is an efficient, distributed protocol that operates with partial knowledge of the group membership and restricted network topology information. One of the major strategies in TBCP is to reduce convergence time by building as good a tree as possible early on, given the restricted membership/topology information available at the different nodes of the tree. We analyse our TBCP protocol by means of simulations, which shows its suitability for purpose.