N. Blefari-Melazzi

University of Rome Tor Vergata, Roma, Latium, Italy

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Publications (122)31.12 Total impact

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    ABSTRACT: In this paper we consider a Wireless Mesh Network (WMN) integrating SDN principles. The Wireless Mesh Routers (WMR) are OpenFlow capable switches that can be controlled by SDN controllers, according to the wmSDN (wireless mesh SDN) architecture that we have introduced in a previous work. We consider the issue of controller selection in a scenario with intermittent connectivity. We assume that over time a single WMN can become split in two or more partitions and that separate partitions can merge into a larger one. We assume that a set of SDN controllers can potentially take control of the WMRs. At a given time only one controller should be the master of a WMR and it should be the most appropriate one according to some metric. We argue that the state of the art solutions for "master election" among distributed controllers are not suitable in a mesh networking environment, as they could easily be affected by inconsistencies. We envisage a "master selection" approach which is under the control of each WMR, and guarantees that at a given time only one controller will be master of a WMR. We designed a specific master selection procedure which is very simple in terms of the control logic to be executed in the WMR. We have implemented the proposed solution and deployed it over a network emulator (CORE) and over the combination of two physical wireless testbeds (NITOS and wiLab.t).
    06/2014;
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    ABSTRACT: Information Centric Networking (ICN) is paradigm in which the network layer provides users with content addressed "by name". In-network caching is one of the key functionality to be provided by ICN nodes. To avoid network nodes caching fake contents, it is necessary to verify the validity of data items. A content is deemed to be valid if it verifies three properties: i) integrity: it has not be modified; ii) provenance: it comes from the intended source; iii) relevance: it is indeed the content requested from the user (by using the name of that content). In this paper, we discuss the interplay among three pivotal ICN aspects: caching, validity and naming. Specifically, we will investigate different naming and digital signature schemes, evaluating their speed, overhead and their impact on caching performance. Perhaps counter-intuitively, we find that the relatively slow verification time of today's signatures, which bottlenecks the rate of storing new data items in the network caches, does not come as a critical shortcoming, but may actually even improve the cache hit probability when the LRU caching policy is employed.
    IEEE GLOBECOM 2013, Atlanta, GA; 12/2013
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    Bruno Ricci, Andrea Detti, Nicola Blefari-Melazzi
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    ABSTRACT: Information Centric Networking (ICN) is a new paradigm in which the network layer provides users with content exposed as names, instead of providing communication channels between hosts. We present a P2P application for the live streaming of video contents encoded at multiple bit-rates. The application enables a limited set of neighboring cellular devices to increase the quality of video playback, by cooperatively using their cellular (e.g. 3G) and proximity (e.g. Wi-Fi Direct) wireless connections. The application exploits key functionalities of ICN: routing by name, in network caching and multicast delivery. We developed a prototype of the application and assessed its performance in a test-bed based on Linux devices with 3G connections, the CCNx tool, the VLC player and the MPEG DASH streaming format. Our main contribution is to show how ICN can provide support to emerging video streaming applications, and ease their creation.
    24th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, London, United Kingdom; 09/2013
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    ABSTRACT: Information Centric Networking (ICN) has been proposed as a new networking paradigm in which the network provides users with content instead communication channels between hosts. The Software Defined Networking (SDN) approach promises to be a solution to enable the continuous evolution of networking architectures. In this paper we propose and discuss solutions to support ICN using SDN concepts. We focus on an ICN framework called CONET, which grounds its roots in the CCN/NDN architecture. We face the problem in two complementary ways. First we discuss a general and long term solution based on SDN concepts without taking into account specific limitations of SDN standards and equipment. Then we focus on an experiment to support ICN functionality over a large scale SDN testbed based on OpenFlow, developed in the context of the OFELIA European research project. The current OFELIA testbed is based on OpenFlow 1.0 equipment from a variety of vendors, therefore we had to design the experiment taking into account the features that are currently available on off-the-shelf OpenFlow equipment.
    01/2013;
  • A. Detti, C. Pisa, S. Salsano, N. Blefari-Melazzi
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    ABSTRACT: In this paper we propose to integrate Software Defined Networking (SDN) principles in Wireless Mesh Networks (WMN) formed by OpenFlow switches. The use of a centralized network controller and the ability to setup arbitrary paths for data flows make SDN a handy tool to deploy fine-grained traffic engineering algorithms in WMNs. However, centralized control may be harmful in multi-hop radio networks formed by commodity devices (e.g. Wireless Community Networks), in which node isolation and network fragmentation are not rare events. To exploit the pros and mitigate the cons, our framework uses the traditional OpenFlow centralized controller to engineer the routing of data traffic, while it uses a distributed controller based on OLSR to route: i) OpenFlow control traffic, ii) data traffic, in case of central controller failure. We implemented and tested our Wireless Mesh Software Defined Network (wmSDN) showing its applicability to a traffic engineering use-case, in which the controller logic balances outgoing traffic among the Internet gateways of the mesh. Albeit simple, this use case allows showing a possible usage of SDN that improves user performance with respect to the case of a traditional mesh with IP forwarding and OLSR routing. The wmSDN software toolkit is formed by Open vSwitch, POX controller, OLSR daemon and our own Bash and Python scripts. The tests have been carried out in an emulation environment based on Linux Containers, NS3 and CORE tools.
    Wireless and Mobile Computing, Networking and Communications (WiMob), 2013 IEEE 9th International Conference on; 01/2013
  • A. Detti, M. Pomposini, N. Blefari-Melazzi, S. Salsano
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    ABSTRACT: Information Centric Networking (ICN) is a new paradigm in which the network layer provides users with content, instead of providing communication channels between hosts, and is aware of the name (or identifiers) of the contents. A fundamental ICN operation is the routing of content requests towards a node that is able to provide the requested content. To meet this goal, different routing architectures have been proposed so far.In this paper, we consider a network that uses a routing-by-name architecture, i.e. content requests are routed on the base of the content name by using a name-based routing table. We focus on the scenario of fetching Web contents, assuming to use ICN in place of traditional TCP/IP means. In this scenario we need to handle tens of billions of name-based routes, due to the high numbers of Web contents and to the limited aggregability of their names. Consequently, re-using the existing architecture of an IP router would result in two severe problems. First, the current Forwarding Information Base (FIB) technology is unable to contain all name-based routes. Second, implementing a so large Routing Information Base (RIB) requires a very costly hardware. In order to overcome these problems, we propose a routing-by-name architecture, named Lookup-and-Cache, where the FIB is used as a cache of routes, while the RIB is stored in a remote and centralized routing engine. By analyzing real Internet traces, we prove the effectiveness of the proposed architecture, which we also show to be feasible with current technology. In fact, our ICN nodes require to have only a limited set of routes in their FIB, even when supporting a high number of traffic flows.We have implemented our proposed Lookup-and-Cache solution within the CCNx software framework and we used this implementation to assess system performance, such as download delay, lookup rate and fairness.The paper is completed with a discussion on how ICN can be used not only to fetch Web contents but also for other scenarios.
    Computer Networks. 11/2012; 56(17):3705–3722.
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    ABSTRACT: In this paper we present a cooperative video streaming application running on top of an “Information Centric Network” (ICN). The application could be used on mobile devices to offload the cellular radio interface. We demonstrate our application in a test-bed exploiting the CCNx software implementation of an ICN, the VideoLan tool and the Apple HTTP Live Streaming format.
    World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2012 IEEE International Symposium on a; 01/2012
  • L. Veltri, G. Morabito, S. Salsano, N. Blefari-Melazzi, A. Detti
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    ABSTRACT: The Information-Centric Networking (ICN) paradigm is expected to be one of the major innovation of the Future Internet An ICN can be characterized by some key components like: (i) the content-centric request/reply paradigm for data distribution, (ii) route-by-name operations, and (iii) in-network caching. In this paper we focus on a framework for ICN called CONET (COntent NETwork) and in particular on a solution devised under this framework called coCONET. coCONET characteristics make it suitable for deployment in accordance to the Software Defined Networks (SDN) philosophy. In this paper, we will describe how coCONET can be implemented over an OpenFlow (the most popular SDN instantiation, to date) network and how OpenFlow should be modified to better suit the operations of coCONET and, more in general, of ICN solutions.
    Communications (ICC), 2012 IEEE International Conference on; 01/2012
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    ABSTRACT: In this work we assess the delay performance of a Publish Subscribe system built on top of a Delay Tolerant Network (DTN) composed of nodes with limited storage capacities. Many DTN routing protocols replicate the same data over several nodes, in order to deliver data to destination in a faster or in a more reliable way. Of course, increasing the number of replicas has the effect of decreasing the delivery delay perceived by the users, but increases the use of the system memory. Our goal is to investigate the trade-off between reduction of delay and storage requirements when nodes are memory constrained, in a Topic-based, Publish Subscribe system where we have different topics with different popularity. We provide some insights in this trade-off, which implies some unanticipated issues, and propose simple rules to dimension the number of replicas per topic. To this end, we derive analytical models and we validate them with simulations.
    Ad Hoc Networking Workshop (Med-Hoc-Net), 2011 The 10th IFIP Annual Mediterranean; 07/2011
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    Andrea Detti, Nicola Blefari-Melazzi, Ibrahim Habib, Alessandro Ordine
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    ABSTRACT: The 802.11 DCF protocol was devised to achieve per-station fairness; conversely, an harsh per-station unfairness occurs when DCF is loaded by TCP traffic. We aim at extending theoretical knowledge on this fairness issue and at restoring per-station fairness. The contribution of the paper is threefold. First, we introduce two findings: (i) changing the physical transmission rate of the stations does not impact the per-station fairness; (ii) packet queuing occurs in the uplink buffer of a station and has a non-negligible impact on the fairness. Second, we derive a model for evaluating fairness performance. Our model accounts for the effect of several parameters and scenarios that no other model captures in a single analytic framework. Third, and finally, we propose a technique to enforce fairness, which is easy to deploy in real systems, without having to modify existing devices. Experimental results obtained with commercial devices confirm the validity of our solution and findings. Albeit the focus of this paper is on per-station (throughput) fairness, our technique can be easily modified, e.g. to enforce time-based fairness, or per-direction or per-flow fairness.
    Computer Networks. 01/2011; 55:1820-1833.
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    ABSTRACT: The aim of this extended abstract is to present Campus++, a location-based publish-subscribe system for intermittently connected delay tolerant networks, exploiting IEEE 802.15.4 devices, and taking into due account the severe constraints deriving from their physical characteristics. We describe our proposed architectural model and how we implemented our solution in a real test-bed. We point out that our system can be easily adapted to operate in a fully distributed, infrastructure-less way, allowing free communications e.g. in disaster areas or in areas in which ”usual” communications means are either non existent or intentionally made unavailable.
    Proceedings of the 8th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks, SECON 2011, June 27-30, 2011, Salt Lake City, UT, USA; 01/2011
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    ABSTRACT: The aim of this work is to present Campus++, a location-based publish-subscribe system for intermittently connected delay tolerant networks, exploiting IEEE 802.15.4 devices, and taking into due account the severe constraints deriving from their physical characteristics. We describe our proposed architectural model and how we implemented our solution in a real test-bed. We investigate the trade-off between reduction of delay and storage requirements when nodes are memory-constrained. We provide some insights in this trade-off and propose simple rules to dimension the number of replicas per topic. To this end, we derive analytical models and we validate them with simulations. We point out that our system can be easily adapted to operate in a fully distributed, infrastructure-less way, allowing free communications e.g. in disaster areas or in areas in which "usual" communications means are either non existent or intentionally made unavailable.
    Proceedings of the 8th ACM Symposium on Performance evaluation of wireless ad hoc, sensor, and ubiquitous networks, PE-WASUN 2011, Miami Beach, Florida, USA, October 31 - November 4, 2011; 01/2011
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    Andrea Detti, Nicola Blefari-Melazzi
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    ABSTRACT: Nowadays most people exploit the Internet to get contents such as web pages, music or video files. These users only value “what” they download and are not interested about “where” content is actually stored. The IP layer does the opposite and cares about the “where” and not about the “what”. This contrast between the actual usage of the Internet and the service offered by the IP layer is deemed to be the source of several problems concerning usability, performance, security and mobility issues. To overcome this contrast, research on the Future Internet is exploring novel so-called content-centric architectures, where the network layer directly provides users with contents, instead of providing communication channels between hosts. In this paper, we identify the main functionalities of a content-centric network (CONET), we discuss pros and cons of literature proposals for an innovative, content-centric network layer and we draw our conclusions, stating some general requirements that, in our opinion, a CONET should satisfy. KeywordsContent-distribution networks-Domain names-IP-Content routing
    12/2010: pages 359-369;
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    ABSTRACT: The availability of IP traffic monitoring data is of great importance to network operators, researchers and law enforcement agencies. However, privacy legislation, commercial concerns and their implications constitute an impediment in the exploitation of such data. In order to allow compliance to the derived issues and protect privacy without compromising information usability, this chapter leverages findings from two separate research initiatives and aims at paving the way towards a unified approach for privacy-aware collection, processing and exchange of data that stem from network monitoring activities. It investigates the fundamental principles and requirements for a privacy-aware ontological model in the semantic domain of monitoring-data management and exchange, as well as a rule-based approach in specifying the appropriate privacy policies, and enables a clean separation between data models and security semantics. It pursues the definition of the appropriate structures for seamlessly introducing privacy awareness in network monitoring ontologies, including user context, intended usage purpose, data age and privacy obligations. Such an approach enables to transfer the expressiveness of legislation rules into the model and allow their automatic processing. KeywordsNetwork monitoring-Privacy-Ontology
    12/2010: pages 317-331;
  • Computer and Information Sciences - Proceedings of the 25th International Symposium on Computer and Information Sciences, London, UK, September 22-24, 2010; 01/2010
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    IEEE Trans. Parallel Distrib. Syst. 01/2010; 21:857-871.
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    Andrea Detti, Pierpaolo Loreti, Nicola Blefari-Melazzi, Francesco Fedi
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    ABSTRACT: The Data Distribution Service (DDS) middleware is enjoying a rapid adoption in high-performance, mission-critical networks. At the same time, the H.264 Scalable Video Coding (SVC) has been recently standardized and it is deemed to be an effective solution for video streaming over a channel with time-varying bandwidth, like the wireless one. In these conditions, it is critical to adapt the video bit-rate to the actual wireless capacity, and bit-rate adaptation is extremely simple for a H.264 SVC video. In this paper we devise, evaluate and demonstrate a technique for streaming H.264 SVC video over a DDS middleware. The contribution is threefold: i) we design a structure of the DDS data-unit able to carry H.264 SVC video-units; ii) we devise a receiver-driven rate-control mechanism based on our DDS data-unit and exploiting specific DDS functionality; iii) we implement and show the effectiveness of our mechanism in an 802.11 wireless scenario, comparing our proposal with other solutions.
    11th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WOWMOM 2010, Montreal, QC, Canada, 14-17 June, 2010; 01/2010
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    A. Detti, N. Blefari-Melazzi
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    ABSTRACT: In this paper we evaluate analytically the average occupancy of the transmission buffer of a 802.11 station (STA). The station belongs to a Wi-Fi Hot-Spot and exchanges data with a fixed host. The data exchange is regulated by the Transmission Control Protocol (TCP). The research interest is motivated by the fact that several papers assume that in these conditions the STA buffer is nearly empty. On the contrary, we prove that this assumption may be wrong and discuss the consequences of this fact. We test the proposed model by means of ns2 simulation, ascertain its accuracy, and highlight its limits.
    IEEE Transactions on Wireless Communications 03/2009; · 2.42 Impact Factor
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    ABSTRACT: This paper addresses the following foundational question: what is the maximum theoretical delay performance achievable by an overlay peer-to-peer streaming system where the streamed content is subdivided into chunks? As shown in this paper, when posed for chunk-based systems, and as a consequence of the store-and-forward way in which chunks are delivered across the network, this question has a fundamentally different answer with respect to the case of systems where the streamed content is distributed through one or more flows (sub-streams). To circumvent the complexity emerging when directly dealing with delay, we express performance in term of a convenient metric, called "stream diffusion metric". We show that it is directly related to the end-to-end minimum delay achievable in a P2P streaming network. In a homogeneous scenario, we derive a performance bound for such metric, and we show how this bound relates to two fundamental parameters: the upload bandwidth available at each node, and the number of neighbors a node may deliver chunks to. In this bound, k-step Fibonacci sequences do emerge, and appear to set the fundamental laws that characterize the optimal operation of chunk-based systems. Comment: 8 pages, 5 figures
    02/2009;
  • N. Blefari-Melazzi, J.N. Daigle, M. Femminella
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    ABSTRACT: A critical issue for the convergence of telephone networks towards an all IP environment is the provisioning of an adequate QoS level to the telephone traffic. Following the guidelines detailed in RFC 2990, we recently proposed an admission control function, named Gauge & Gate Reservation with Independent Probing (GRIP), through which we are able to provide QoS guarantees by means of stateless procedures compliant within the Differentiated Service (DiffServ) paradigm, which is the de facto standard for QoS provisioning in Internet. The main goal of this paper is to present a specific implementation of GRIP optimized for supporting voice over IP (VoIP) services within a DiffServ cloud. In particular, we propose and analyze a simple measurement-based call admission control procedure for carrying VoIP traffic in a DiffServ environment. We assume voice sources are leaky bucket controlled with known leaky bucket parameters. We analyze the leaky bucket to derive the distribution of the times over which voice sources generate traffic at peak and regulated rates. We use the results of that analysis, which provides complete knowledge of the traffic generation characteristics of a single source, to derive a Markov chain model that characterizes the voice packet generation process of a single voice source. We then derive a simple stateless threshold policy for admission control; that is, our policy is of the form if, at admission request time,x⩽xthreshold, admit the call; else reject the call. Finally, we show, via simulation, that the QoS achieved using the threshold-based admission control policy is very close to that achieved by a stateful admission control policy even at very high traffic utilization.
    Computer Networks. 01/2009;

Publication Stats

438 Citations
31.12 Total Impact Points

Institutions

  • 1994–2013
    • University of Rome Tor Vergata
      • • Dipartimento di Ingegneria Civile e Ingegneria Informatica (DICII)
      • • Dipartimento di Ingegneria Elettronica
      Roma, Latium, Italy
  • 2010
    • Consorzio Nazionale Interuniversitario per le Telecomunicazioni
      Genova, Liguria, Italy
  • 1999–2009
    • Università degli Studi di Perugia
      • Department of Electronic and Information Engineering
      Perugia, Umbria, Italy
  • 1994–2007
    • The American University of Rome
      Roma, Latium, Italy
  • 1993–2004
    • Università Degli Studi Roma Tre
      Roma, Latium, Italy
  • 2001–2002
    • Università degli Studi di Palermo
      Palermo, Sicily, Italy