A. Pattavina

Politecnico di Milano, Milano, Lombardy, Italy

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Publications (260)113.82 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We are currently facing two major challenges for the development of future photonic networks: scalability and cost/energy efficiency. The process of evaluating the impact on the network of the expected increase of traffic demand is called scalability analysis. It is one of the most important tasks for a network designer, along with minimizing energy consumption and cost. In this paper, we propose a novel approach to assess Wavelength Switched Optical Network (WSON) scalability and efficiency. Our method takes into account the routing constraints of Reconfigurable Optical Add/Drop Multiplexers (ROADMs), a variety of coherent transmission systems, different amplification schemes and types of fibre. We have assessed the network scalability and the roadmap for technological upgrades by running simulations of the recently deployed Telecom Italia’s WSON Kaleidon. We have used realistic traffic profiles and traffic growth-rate projections under a variety of case studies of practical interest. This study provides an innovative tool and insights to drive network designers’ decisions based on the impact of present and future photonic technologies.
    Journal of Lightwave Technology 06/2014; · 2.56 Impact Factor
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    ABSTRACT: Cloud Computing (CC) services are rapidly catching on as an alternative to conventional office-based computing. As cloud computing adoption increases, the energy consumption of the network and of the computing resources that underpin the cloud is growing and causing the emission of enormous quantities of CO2. Research is now focusing on novel "low-carbon" cloud-computing solutions. Renewable energy sources are emerging as a promising solution both to achieve drastic reduction in CO2 emissions and to cope with the growing power requirements of data centers. These infrastructures can be located near renewable energy plants and data can be effectively transferred to these locations via reconfigurable optical networks, based on the principle that data can be moved more efficiently than electricity. This paper focuses on how to dynamically route on-demand optical circuits that are established to transfer energy-intensive data processing towards data centers powered with renewable energy. Our main contribution consists in devising two routing algorithms for connections supporting CC services, aimed at minimizing the CO2 emissions of data centers by following the current availability of renewable energies (e.g., coming from sun and wind). The trade-off with energy consumption for the transport equipments is considered. We also compare three different IP-over-WDM network architectures. The results show that relevant reductions, up to about 30% in CO2 emissions can be achieved using our approaches compared to baseline shortest-path-based routing strategies, paying off only a marginal increase in terms of network blocking probability.
    IEEE Journal on Selected Areas in Communications 01/2014; 32(1):28-38. · 3.12 Impact Factor
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    ABSTRACT: Cloud services are fundamentally supported by data center networks (DCNs). With the fast growth of cloud services, the scale of DCNs is increasing rapidly, leading to great concern about system scalability due to multiple constraints. This paper proposes a scalable DCN architecture based on optical switching and transmission, with the distributed placement of optical switches and server racks at different nodes in a given optical network. This solves the scalability issue by relaxing power and cooling constraints and by reducing the number of (electronic) switches using high-capacity optical switches, as well as by simplifying DCN internal connections using wavelengths in the optical network. Moreover, the distributed optical switches provide service access interfaces to meet demand within areas, and thus reduce the transmission cost of the external traffic. The major concern is the additional delay and cost for remote transmissions of the DCN internal traffic. To this end, we study the component placement problem in DCNs under a given set of external demands and internal traffic patterns. By leveraging among multiple conflicting factors such as scalability and internal overhead of the DCN as well as the transmission cost of external traffic, we propose both an integer linear program and a heuristic to minimize the system cost of a DCN while satisfying all service demands in the network. This addresses both scalability and cost minimization issues from a network point of view.
    Journal of Optical Communications and Networking 01/2014; 6(3):270-281. · 1.43 Impact Factor
  • Fotonica 2013; 05/2013
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    ABSTRACT: Novel distance-adaptive optical transmission technologies have been proposed to boost transceiver datarates and to enable more flexibility in the allocation of traffic flows. The application of this new class of transceivers is being widely investigated in core networks, while their suitability in the metro area is still an open issue. On one hand, the short metro distances enable the utilization of higher spectrally efficient modulation formats, on the other hand, the lower bitrate suggests to employ lower baud rate with respect to core networks. In this letter, we perform traffic grooming and spectrum assignment using transceivers with fixed baud rate of 28 and 14 GBd and distance-adaptive modulation formats in optical metro networks. Comparisons with the wavelength-division multiplexing systems running over a fixed grid show that 1) significant savings in terms of spectrum occupation can be achieved, and that 2) such savings can be effectively achieved also using lower baud rate transceivers (e.g., 14 GBd).
    IEEE Photonics Technology Letters 01/2013; 25(2):183-186. · 2.04 Impact Factor
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    ABSTRACT: The ICT (Information and Communication Technology) sector has recently been identified as a growing contributor to worldwide greenhouse gases emissions and power consumption. This has triggered interest for more energy efficient ways to design and operate telecommunication networks. We present an overview of the solutions proposed within the European network of excellence TREND focusing on core and metro networks including data centers. Potential savings are presented and discussed with respect to their impact and applicability within the global picture.
    Digital Communications - Green ICT (TIWDC), 2013 24th Tyrrhenian International Workshop on; 01/2013
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    ABSTRACT: In this paper we evaluate the potential of Quality of Protection (QoP) schemes to improve the energy efficiency in optical transport networks. Different levels of flexibility, both in the digital and optical domains, are considered for simulations over a nation-wide reference network model. Increasing power savings are achieved as long as the flexibility levels become higher, demonstrating the benefits of QoP deployments to accomplish power consumption reduction.
    Design of Reliable Communication Networks (DRCN), 2013 9th International Conference on the; 01/2013
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    ABSTRACT: The ever-increasing Internet traffic demand introduces new challenges for telecommunications carriers. Telecom networks will have to be upgraded to cope with the new capacity requirements. However, deploying enough capacity is not the only requirement for network operators. The impact of new technologies in terms of capital investment and energy consumption becomes a key issue. There is a special interest in investigating new mechanisms and technologies to improve the energy efficiency of future networks, while maintaining the high reliability and service availability of current optical transport networks. This article evaluates the energy- and cost-efficiency of an innovative flexible-grid orthogonal-frequency-division-multiplexing (OFDM) -based network and compares them with those for conventional wavelength-division-multiplexing (WDM) networks. Due to the importance of resilience in optical transport networks, the study considers and evaluates different protection schemes. The results demonstrate the potential energy efficiency improvements that can be achieved by an elastic OFDM-based technology, especially when a shared protection scheme is adopted, and give an insight into the potential cost benefits that such a novel technology can offer to telecommunication carriers.
    Optical Switching and Networking 01/2013; · 0.72 Impact Factor
  • M. De Andrade, M. Tornatore, A. Pattavina
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    ABSTRACT: Future passive optical networks (PONs) are expected to support much larger capacity and much wider coverage. How to jointly address these two design requirements represents one of the most challenging aspects in today's research on PONs. So far, most research efforts have been devoted to devising new architectural or technological solutionsto support such stringent requirements. In particular, the technology to be used for transmission may have diverse multiplexing techniques, types of transceivers, modulation formats, and detection techniques. However, the question of which transmission technology is the most effective considering the trade-offs in terms of complexity, offered capacity, and reach is still open. In this paper, we aim at answering this question comparing the use of time division multiplexing (TDM), wavelength division multiplexing (WDM), and hybrid TDM/WDM techniques in PONs. To achieve this goal, we first categorize the main options for transmission technologies in PONs in three families: colored dense WDM (DWDM), tunable DWDM, and colorless DWDM. Then, we propose a new optimization scheme that selects the optimal transmission technology for different operational scenarios that are defined by varying the number of users, the distance to the users, and the traffic load. The choice of the passive optical components to be used at the remote node is also part of the optimization scheme given its significant impact on the choiceof the transmission technology. As a result, we report and discuss which transmission technologies are the most suitable under different operational scenarios.
    Journal of Optical Communications and Networking 01/2013; 5(9):1010-1020. · 1.43 Impact Factor
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    ABSTRACT: Future telecommunication networks will be designed to guarantee energy-efficiency and sustainability. Optical networks, given their capability to switch and transport large traffic amounts for a relatively-limited energy consumption, are expected to play an increasingly important role in the evolution towards energy efficiency. While traditional optical network design strategies are aimed at minimizing Capital Expenditures (CapEx), i.e., the cost associated to network equipment, several research studies have recently proposed novel strategies targeting the reduction of Operational Expenditures (OpEx) mainly identified with the network energy consumption. We compare two possible switching paradigms in optical networks, i.e., circuit switching (at the optical layer) and packet switching (at the electronic/IP layer). For each of them, we first provide novel network design strategies that minimize CapEx or OpEx and then we quantitatively identify and discuss under which conditions (network size, load, etc.) one paradigm is more convenient than the other from a cost and/or power consumption perspective.
    Optical Network Design and Modeling (ONDM), 2013 17th International Conference on; 01/2013
  • Proc. of the OnlineGreenComm, online conference; 01/2013
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    ABSTRACT: Recently, the need for energy-efficient and sustainable capacity growth has become stringent for telecommunication networks and great efforts have been produced to reduce their power consumption. Optical technologies based on Wavelength Division Multiplexing are well-recognized as a promising solution for greening the future Internet. One relevant approach to achieve such power savings consists in aggregating traffic flows in few network links, so that power can be saved by switching-off some unused network devices. However, the need to ensure network resiliency against link and/or node failures imposes that still the resources reserved to protect connections become available immediately after a failure occurs. Therefore, a possible solution is to set some devices into low-power sleep-mode, so that they can be rapidly re-activated and provide fast connection recovery.In this paper we focus on the power-efficiency of protected IP-over-WDM networks and provide a comprehensive comparison of four different protection strategies, namely Shared-Link, Shared-Path, Dedicated-Link and Dedicated-Path Protection SLP, SPP, DLP and DPP respectively in a sleep-mode scenario. In the proposed design strategies we assume that low-power sleep-mode is enabled for devices used for protection. Mathematical models for a power-aware design with sleep-mode is proposed for the four protection strategies. We show that relevant power savings up to about 60% can be obtained for all the protection strategies by setting protection devices into sleep-mode.
    Journal of High Speed Networks 01/2013; 19(1):19-32. · 0.38 Impact Factor
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    ABSTRACT: The quest of extended optical reach has been one of the major drivers for the transmission systems research field. Since extending the optical reach does not come for free and that reducing the power consumption has become a mandatory task for network designers, we investigate IP-over-WDM network power consumption as a function of 100 Gb/s Transponders' (TXP) transmission reach. In order to achieve this target, we propose a novel analytical model that captures the increase of TXP power consumption versus its optical reach. Network design is performed via a Mixed Integer Linear Programming (MILP) optimization engine. We have used two Multi-Layer design strategies, the Bypass (Bp) and the Direct-Bypass (DBp), that we have both applied to the “All-On” and the “On-Off” planning approaches: the former considers that transmission devices are always on and provides an upper bound to the network power consumption whereas the latter maximizes power savings by switching network devices On-Off according to daily traffic variations. Finally, simulations on a European-like backbone network show that there exists an optical reach that leads to a minimum network power consumption, the so-called optimal reach. By performing network design at the optimal reach we can achieve up to 36% and 37% of energy savings with respect to an extended reach-based design in the All-On and in the On-Off planning respectively.
    Journal of Lightwave Technology 01/2013; 31(11):1828-1834. · 2.56 Impact Factor
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    ABSTRACT: Data center networks (DCNs) generally adopt Clos network with crossbar middle switches to achieve non-blocking data switching among the servers, and the number of middle switches is proportional to the number of ports of the aggregation switches in a fixed manner. Besides, reconfiguration overhead of the switches is generally ignored, which may contradict the engineering practice. In this paper, we consider batch scheduling based packet switching in DCNs with reconfiguration overhead at each middle switch, which inevitably leads to packet delay. With existing state-of-the-art traffic matrix decomposition algorithms, we can generate a set of permutations, each of which stands for the configuration of a middle switch. By reconfiguring each middle switch to fulfill multiple configurations in parallel with others, we reveal that a tradeoff exists between packet delay and switch cost (denoted by the number of middle switches), while performance guaranteed switching with bounded packet delay can be achieved without any packet loss. Based on the tradeoff, we can minimize the number of middle switches (under a given packet delay bound) and an overall cost metric (by translating delay into a comparable cost factor), as well as formulating criterions for choosing a matrix decomposition algorithm. This provides a flexible way to reduce the number of middle switches by slightly enlarging the packet delay bound.
    High Performance Switching and Routing (HPSR), 2013 IEEE 14th International Conference on; 01/2013
  • D.G. Garao, G. Maier, A. Pattavina
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    ABSTRACT: Interconnection systems inside switching equipment, high-performance computers and data-centers are nowadays facing more and more demanding requirements. Optical interconnections based on multistage switching networks provide more bandwidth and less energy consumption compared to electronic counterparts. In this work a procedure to design the architecture of optical multistage switching networks is proposed which exploits the properties of multistage networks, on one side, and of optical switching systems on the other side. Thanks to the modularity of the architecture, a generic-size fabric can be implemented by simply cascading multiple stage-modules. In this paper we show in details the application of the approach to the Extended Generalized Shuffle (EGS) networks, though the method can be extended to other types of networks. The proposed procedure supports various implementation technologies, as, for example, integrated optics with micro-ring resonators, free- space optics with 2-D MEMS, networks on chip.
    Computer Communications and Networks (ICCCN), 2013 22nd International Conference on; 01/2013
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    ABSTRACT: A differentiated quality of protection scheme is evaluated in terms of energy efficiency for fixed-grid WDM and flexible-grid OFDM-based networks. Significant energy savings can be achieved by exploiting the heterogeneous protection requirements.
    Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2013; 01/2013
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    ABSTRACT: Cloud services are fundamentally supported by Data Center Networks (DCNs). With the fast growth of cloud services, the scale of DCNs increases rapidly, leading to a big concern on system scalability due to multiple constraints. Based on optical switching and transmission, this paper proposes a scalable DCN architecture with distributed placement of optical switches and server racks at different nodes in a given optical network. This solves the scalability issue by relaxing power and cooling constraints, and reducing the number of (electronic) switches using high-capacity optical switches, as well as simplifying internal connections of the DCN using wavelengths in the optical network. Moreover, the distributed optical switches provide service access interfaces to demands in vicinities, and thus reduce the transmission cost of the external traffic. The major concern is the additional delay and cost for remote transmissions of the DCN internal traffic. To this end, we study the component placement problem in DCNs under a given set of external demands and internal traffic patterns. By leveraging among multiple conflicting factors such as scalability and internal overhead of the DCN as well as the transmission cost of external traffic, we propose an ILP (Integer Linear Program) to minimize the overall cost of a DCN while satisfying all service demands in the network. This addresses both scalability and cost minimization issues from a network point of view.
    Communications in China (ICCC), 2013 IEEE/CIC International Conference on; 01/2013
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    ABSTRACT: For decades, optical networks have provided larger bandwidths than could be utilized, but with the increasing growth of the global Internet traffic demand, new optical transmission technologies are required to provide a much higher data rate per channel and to enable more flexibility in the allocation of traffic flow. Currently, researchers are investigating innovative transceiver architectures capable of dynamically adapting the modulation format to the transmission link properties. These transceivers are referred to as elastic and enable flexible allocation of optical bandwidth resources. To exploit their capabilities, the conventional fixed spectrum grid has to evolve to provide a more scalable and flexible system that can provide the spectral resources requireded to serve the client demand. The benefits of elastic transceivers with distance-adaptive data rates have been evaluated in optical core networks, but their application to metro ring networks has still not been addressed. This paper proposes methods based on integer linear programs and heuristic approaches to solve the routing, modulation level, and spectrum assignment problem in optical rings with elastic transceivers and rate-adaptive modulation formats. Moreover, we discuss how to analytically compute feasible solutions that provide useful upper bounds. Results show a significant reduction in terms of transceiver utilization and spectrum occupation.
    Journal of Optical Communications and Networking 01/2013; 5(4):305-315. · 1.43 Impact Factor
  • N. Carapellese, M. Tornatore, A. Pattavina
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    ABSTRACT: The convergence between fixed access networks and mobile backhauling networks is the basis of the evolution towards future Next-Generation Access Networks. Multi-Stage WDM-PONs are the ideal converged infrastructures for carrying both fixed access and mobile backhauling, because they inherit some features of WDM core/metro networks, e.g., large capacity and high transparency. Moreover, they provide support for the “BBU Hotelling” backhauling solution, which consists in separating base stations' Base-Band Units (BBU) from their Remote Radio Heads (RRH), and grouping them into consolidated “Hotels”, with reduced costs and energy consumption. In this work, we propose and model by an ILP formulation the novel “BBU Placement” network optimization problem, on a converged Multi-Stage WDM-PON. The aim is to decide in which nodes to place BBUs, together with the routing and wavelength assignment of traffic demands, such that the number of Hotels is minimized. We capture the importance of the maximum latency of Digitized Radio-over-Fiber (D-RoF) flows exchanged between each BBU and its RRH, which becomes a constraint on the maximum propagation delay of corresponding routes. Simulation results are obtained by generating some random multi-stage tree instances and solving them via CPLEX. The analysis of the number of Hotels versus network sizes and maximum D-RoF delay validates the proposed model and highlights the strong impact of such parameters on the achievable BBU consolidation.
    Optical Network Design and Modeling (ONDM), 2013 17th International Conference on; 01/2013
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    ABSTRACT: We use an analytical formulation based on Markov chains to evaluate blocking and energy-saving performance of a Wavelength Division Multiplexing (WDM) network with transponder power management. We consider three power modes for transponders, i.e., powered-on (ON), idle (sleep) or powered-off (OFF). To guarantee fast provisioning to high priority (e.g., real time) connections, we assume that some idle transponders (that can be re-activated much faster than powered-off transponders) are reserved for such connections. Some other connections may not have strict set-up time constraint, and can wait until a powered-off transponder is activated and available. We find that at least 32% of power savings can be obtained with such management strategy, for an acceptable degradation in the overall network blocking performance.
    Transparent Optical Networks (ICTON), 2013 15th International Conference on; 01/2013

Publication Stats

1k Citations
113.82 Total Impact Points

Institutions

  • 1–2013
    • Politecnico di Milano
      • • Department of Electronics, Information, and Bioengineering
      • • Department of Electrical Engineering
      Milano, Lombardy, Italy
  • 2011
    • Pierre and Marie Curie University - Paris 6
      Lutetia Parisorum, Île-de-France, France
    • CTTC Catalan Telecommunications Technology Centre
      Barcino, Catalonia, Spain
  • 2010
    • University of Peloponnese
      Trípoli, Peloponnese, Greece
    • Alcatel Lucent
      Lutetia Parisorum, Île-de-France, France
  • 2009–2010
    • France Télécom
      Lutetia Parisorum, Île-de-France, France
    • Warsaw University of Technology
      • Institute of Telecommunications
      Warsaw, Masovian Voivodeship, Poland
    • Poznan University of Technology
      • Chair of Communication and Computer Networks
      Poznań, Greater Poland Voivodeship, Poland
    • University of California, Davis
      • Department of Computer Science
      Davis, CA, United States
  • 2007–2010
    • Tohoku University
      • Graduate School of Science
      Sendai-shi, Miyagi-ken, Japan
    • CSU Mentor
      Long Beach, California, United States
  • 2008–2009
    • Università degli Studi di Trento
      • Department of Information Engineering and Computer Science
      Trient, Trentino-Alto Adige, Italy
    • ParisTech
      Lutetia Parisorum, Île-de-France, France
  • 2006
    • Eurofins, Italy
      Milano, Lombardy, Italy
  • 1988–1992
    • The American University of Rome
      Roma, Latium, Italy
  • 1987–1988
    • Sapienza University of Rome
      Roma, Latium, Italy