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The emergence of 5G technologies opens up new opportunities for railway communications. One of the foundational aspects of 5G architecture is its control-plane programmability, which can be achieved through Software Defined Networking (SDN). In railway scenarios, this can be used to dynamically reconfigure the network for a more effective and efficient management of communication flows produced by moving trains. The paper presents a framework for integrating modelling and analysis tools into a programmable control plane specifically tailored to railway communications. We introduce the concept of domain-awareness in the network control plane as an SDN-enabled feature that allows achieving application-specific advantages besides those purely expressed in terms of key performance indicators such as the quality of service. We propose a reference architecture in which domain-awareness in the control plane is obtained by considering information gathered by network devices and ad-hoc communication gateways that are able to detect relevant signalling events. In the architecture, the actual behaviour of the SDN controller is governed by applications that are able to react to specific triggers and re-configure network devices accordingly. We also provide a methodological framework based on model-driven engineering and formal methods, including dynamic state machines, for the automatic generation of SDN control plane logic.

Distribution of live multimedia streams to a high number of end users through an ISP network may be efficiently implemented through IP multicasting. Multicast traffic engineering with traditional decentralized approaches, however, is still a challenging problem for network operators. In this article we present a centralized approach to management of source-specific multicast traffic flows relying on software defined networking. Our approach is suitable for hybrid IP/SDN networks, where network nodes behave as traditional IP routers by default, but whose packet forwarding behavior may be customized for specific flows thanks to an OpenFlow-enabled control plane. We also describe a traffic management system that we implemented as a proof of concept, which can be used by an ISP to compute multicast distribution trees for a given set of channels to be distributed to their customers.

Creating large scale testbeds for evaluating wireless mesh technologies and protocols, and for testing their ability to support real world applications in realistic environments, is a crucial step towards the ultimate success of the WMN paradigm. In this paper we suggest the hierarchical federation of a planetary scale infrastructure, such as PlanetLab, with a number of local OMF-based wireless testbeds as a viable approach towards this goal. Along such direction, we present an architectural model for integrating at the technical level these two kinds of infrastructures and our initial implementation of such a model. We also present some test case experiments we run on our initial implementation of the integrated architecture, to illustrate how an experiment on peer-to-peer traffic optimization can be executed by combining both wireless nodes of a OMF-based testbed and PlanetLab nodes located across Europe. The possibility of running this kind of experiments in such a hybrid experimental scenario highlighted several real-world issues that are worth to be further investigated.

Distributed research testbeds play a fundamental role in the evaluation of disruptive innovations for the Future Internet. In recent years, the main research funding agencies have promoted several initiatives aimed at designing and building open, large scale, realistic experimental facilities that could be used to evaluate innovative networking architectures, paradigms and services. In this paper, after discussing the main challenges in building such infrastructures, we present how, by leveraging the concept of federation, we managed to introduce a first degree of heterogeneity into PlanetLab Europe, a European testbed federated with PlanetLab, by providing UMTS connectivity to PlanetLab Europe nodes. Our contribution is just a first step of an evolutionary path whose further developments will lead to next generation large-scale heterogeneous testbeds for supporting experimentally-driven research on the Network of the Future (Preliminary results within the same framework of this work have been recently published in Canonico et al. (2007) and Botta et al. (2008)).

Cloud Computing has risen a great interest over the last years as it represents an enabling technology for flexible and ubiquitous access over the network to a set of shared computing resources. This work comes from an industrial experience aiming at exploiting the cloud potential for virtualizing complex infrastructures such as an entire Air Traffic Center (ATC), a clear example of complex SoS (System of Systems). The use of virtualization is convenient because industry can leverage in-house test-beds to perform distributed testing campaigns in pre-operational phases or to design new automatic fail-over mechanisms for fully distributed systems. In order to realize such mitigation and recovery techniques in the ATC field, indeed, a cloud platform is required to guarantee a low VM provisioning time with the objective of minimizing the service disruption. In this perspective, after having introduced the principal concepts and factors of the provisioning time, we propose a deep analysis and comparison for two different Infrastructure-as-a-Service (IaaS) platforms, namely Open Stack and Open Nebula (using KVM as hypervisor), that were selected through a preliminary scouting phase.

Simulation has been the most widely used approach for performance evaluation of peer-to-peer applications because it represents a fast and inexpensive way to test novel solutions. Nonetheless, the growing complexity and heterogeneity of the emerging scenario for peer-to-peer applications has made it necessary to validate models and simulation results through experimental evaluation in realistic settings. Performing an experimental evaluation of distributed applications on a large scale, however, is still a challenging task. Firstly, it requires resources which should be made available to the community of researchers through a cooperative effort of institutions. Secondly, but not least important, it should be conducted with a sound methodology and produce results that could be analysed and reused by the whole community of researchers. Our call for papers explicitly asked for contributions illustrating either experiences in conducting real-world experimental analysis of peer-to-peer applications or innovative methodologies that could be useful for assessing such applications with respect to non-functional requirements, such as performance, scalability, fault tolerance, availability and security. This editorial presents the main contributions provided by the six papers that we present in this special issue on.

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.

Software Defined Networking (SDN in short) is reshaping the future of computer networks. By decoupling control and data planes, SDN technologies allow a more flexible management of network infrastructures, whose resources may be operated by means of a well defined programming interface. Several approaches have been recently proposed to implement the SDN concept. OpenFlow is maybe the most prominent SDN component, having been supported by several device vendors. This paper discusses a practical experience in designing an OpenFlow controller for a Mobile Cloud Management system. We present the programming model and the designed abstraction and discuss the lesson learned.

Ubiquitous network access allows people to access an ever increasing range of services from a variety of mobile terminals, including laptops, tablets and smartphones. A flexible and economically efficient way of provisioning such services is through Cloud Computing. Assuming that several cloud-enabled datacenters are made available at the edges of the Internet, service providers may take advantage of them by optimally locating service instances as close as possible to their users. By localizing traffic at the edges of access networks, such an approach may result beneficial for both service and network providers. In this paper we present Follow-Me Cloud (FMC), a technology developed at NEC Laboratories Europe that allows transparent migration of services in TCP/IP networks, thanks to the dynamic configuration of a set of coordinated OpenFlow switches located at the edge of the network. In particular, in this paper we analyze the scalability properties of an FMC-based system and propose a role separation strategy based on distribution of control plane functions which enables scale-out of the system. By means of simulation, we prove that the application of the proposed separation strategy results in less state retained by individual OpenFlow controllers and in more effective localization of network traffic.

Wireless Mesh Networks (WMNs) have recently gained wide attention as a way to provide Internet connectivity in hard-to-reach areas as well as in big cities. The main problem of such networks is their limited bandwidth availability compared to wired networks. Hence, efficient usage of available communication resources is of crucial importance for WMNs. Peer-to-peer applications, these days, produce a considerable amount of traffic over the Internet. Such applications build their own overlay network by not taking into account the topology and the status of the underlying infrastructure, so causing an inefficient utilization of physical communication resources. This problem is particularly severe for Wireless Mesh Networks. In this paper we propose a cross-layer solution for P2P Bittorrent traffic optimization in WMNs, based on the ALTO (Application Layer Traffic Optimization) Service recently defined by the IETF. Our solution is able to significantly optimize Bittorrent traffic and it does not require any modification to the Bittorrent application. The tests we performed show a reduction of about 27% of download time and a reduction of about 66% of traffic crossing the WMN borders.

The success of the Cloud Computing paradigm may be jeopardized by concerns about the risk of misuse of this model aimed at conducting illegal activities. In this paper we address the issue of detecting Denial of Service attacks performed by means of resources acquired on-demand on a Cloud Computing platform. To this purpose, we propose to investigate the consequences of the use of a distributed strategy to detect and block attacks, or other malicious activities, originated by misbehaving customers of a Cloud Computing provider. In order to check the viability of our approach, we also evaluate the impact on performance of our proposed solution. This paper presents the installation and deployment experience of a distributed defence strategy and illustrates the preliminary results of the performance evaluation.

Technological developments of the last few years have favoured the creation of distributed networking infrastructures (usually referred to as Community Networks) where the resources are made available to the members of a community of people. With emerging large-scale community infrastructures the opportunities for new commercial services and for innovative business models are becoming feasible. Since one of the most resource-demanding services today is access to user-generated content through the web, suitable content delivery services are needed in the context of Community Networks in orders to make an effective usage of shared resources. In this paper we describe two architectures we have designed to provide optimized delivery of multimedia web content (e.g. video but also other kinds of User Generated Content) within Community Networks. Both architectures work without any kind of cooperation from the original content providers but assume that a basic web caching service is provided within the network, either by commercial Service Providers or by the community members themselves. While the first architecture relies on a traditional centralized control entity, the second is designed according to the peer-to-peer paradigm, in order to provide better scalability, robustness to failures and self-configurability. Experimental results are also presented aimed at evaluating the performance gains for end-users from a localized distribution of content in scenarios in which community members are distributed in clusters sparse at different geographic locations.

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.

In the last few years many emulation systems have been developed to evaluate the effectiveness of new protocols and applications in realistic and controllable network scenarios. NEPTUNE is a flexible architecture for cluster-based network emulation systems designed and implemented at University of Napoli Federico II. In this poster we present the key components of the NEPTUNE architecture, an in particular the NEPTUNE manager, an open-source software managing the lifecycle of emulation experiments.

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).

A number of distributed applications require communication services with Quality of Service (QoS) guarantees. Work undertaken within the Internet Engineering Task Force (IETF) has led to the definition of novel architectural models for the Internet with QoS support. According to these models, the network has to be appropriately configured in order to provide applications with the needed performance guarantees. In a first proposal, called Integrated Services, applications need to explicitly interact with network routers by means of a signaling protocol (such as RSVP), in order to enforce QoS on a per-flow basis. The Differentiated Services architecture, on the other hand, looks after scalability, thus providing performance guarantees to aggregates of flows. In the case of real-time applications, a hybrid model capable of putting together micro-flow guarantees in the access network and aggregate management in the backbone seems to represent the ideal tradeoff between strict performance and scalability. In this scenario, giving applications a means to interact with the underlying QoS services is of primary importance. Hence, several special-purpose APIs have been defined to let applications negotiate QoS parameters across QoS-capable networks. However, so far, none of these APIs is available for the use of programmers in different operating environments. We believe that such features should be embedded in programming environments for distributed applications. In this work we present how we included QoS control features in a programming language that since years has been adopted for the development of network-based applications: Tcl. We present QTcl, an extension of Tcl, which provides program- mers with a new set of primitives fully compliant with the standard SCRAPI programming interface for the RSVP protocol. We gave QTcl a high portability, in that it enables standard QoS negotiation to be performed in a seamless fashion on the most common operating systems.

International audience; Despite its obvious suitability for distributed multimedia applications, multicasting has not yet found widespread application. Having analyzed shortcomings of today’s approaches, we devise in the GCAP project a new endto- end transport architecture for multimedia multicasting that supports partial order and partial reliability. In this paper, we argue that, at the network layer, single-source multicasting (PIM-SSM) should be chosen. Consequently, our Monomedia Multicast protocol provides, along with reliability and QoS monitoring functionality, an ALM based multicast solution referred to as TBCP (Tree Building Control Protocol), to be used as back channel for SSM, e.g. for retransmission requests. On top of the Monomedia protocol, our Multimedia Multicast protocol handles multimedia sessions composed of multiple monomedia connections: The FPTP (Fully Programmable Transport Protocol) allows applications to specify, through its API, the (global) synchronization and (individual) reliability requirements within a multimedia session. Our group management approach is focused on group integrity.

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.

A number of distributed applications require communication services with Quality of Service (QoS) guarantees. The QoS provisioning issue in the Internet has been addressed by the IETF with the definition of the Integrated Services (IntServ) and Differentiated Services (Diffserv) frameworks. Resource reservation mechanisms on which these models are based are totally time-unaware. Yet, we believe that, in some cases, associating a time interval to network resource reservations could be useful for both users and network providers. In this paper we present a distributed scheme for time-dependent reservations in QoS-enabled IP networks. We also show how the standard signalling protocol RSVP may support this new reservation style, with only a few minor modifications. Finally, we present a first prototype implementation of the major component of the proposed architecture and we provide some hints on future applicability scenarios of the advance reservation paradigm and its impact on related topics such as policing and charging techniques in QoS-enabled IP networks.