Marc De Leenheer

Stanford University, Palo Alto, California, United States

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Publications (86)43.2 Total impact

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    ABSTRACT: Optical Flow Switching (OFS) is promised to be an efficient solution for large Internet data transfers. In this paper, we introduce UltraFlow Access, a novel optical access network architecture that offers dual-mode service to its end-users: IP and OFS. With UltraFlow Access, we design and implement a new control plane and a novel dual-mode network stack to ensure efficient connection setup, and reliable and optimal data transmission. Experimental testbed results demonstrate concurrent error-free transmission of 10 Gbps per-wavelength OFS and 1.25 Gbps conventional IP, delivered over the same infrastructure.
    Transparent Optical Networks (ICTON), 2013 15th International Conference on; 12/2013
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    ABSTRACT: UltraFlow - also known as Optical Flow Switching (OFS) has been recently presented as an effective technology for large Internet data transfer. In this paper, we propose a novel scheduling mechanism for the Stanford UltraFlow access network, a novel optical access network architecture that offers dual-mode service to the end-users: legacy IP and OFS. The proposed scheme is a hybrid mechanism that combines the batch scheduling technique with existing methods so as to increase the average Flow throughput, while maintaining relatively low traffic latency. Extensive simulations highlight the advantages of the proposed solution and demonstrate its merits.
    GLOBECOM 2013 - 2013 IEEE Global Communications Conference; 12/2013
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    ABSTRACT: Today's registration of newborns with congenital cytomegalovirus (cCMV) infection is still performed on paper-based forms in Flanders, Belgium. This process has a large administrative impact. It is important that all screening tests are registered to have a complete idea of the impact of cCMV. Although these registrations are usable in computerised data analysis, these data are not available in a format to perform electronic processing. An online Neonatal Registry (NEOREG) System was designed and developed to access, follow and analyse the data of newborns remotely. It allows remote access and monitoring by the physician. The Java Enterprise layered application provides patients' diagnostic registration and treatment follow-up through a web interface and uses document forms in Portable Document Format (PDF), which incorporate all the elements from the existing forms. Forms are automatically processed to structured EHRs. Modules are included to perform statistical analysis. The design was driven by extendibility, security and usability requirements. The website load time, throughput and execution time of data analysis were evaluated in detail. The NEOREG system is able to replace the existing paper-based CMV records.
    Informatics for Health and Social Care 01/2013; · 0.71 Impact Factor
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    ABSTRACT: Cloud computing, building on the idea of “computation as a public utility” is made possible by the increased network capabilities in terms of bandwidth and reduced latency. The cloud paradigm today sees adoption in many businesses given its advantages, not only from a customer point of view (e.g., universal access to the same applications across all company branches) but also from the application provider and network operator perspective (e.g., software updates no longer need to be distributed). To be able to offer cloud computing services efficiently, service providers need not just an infrastructure comprising both network and IT resources, but especially a control system that is able to orchestrate such integrated network and IT services. This paper offers a new proposal for such a system: an enhanced network control plane, the NCP+, which is based on a GMPLS control plane with a Hierarchical Path Computation Element (PCE) architecture able to jointly make network routing and IT server provisioning decisions. Indeed, in the assumed cloud paradigm, a user generally does not care what exact server the offered service is using, as long as its service requirements are met: thus the anycast principle applies. The paper discusses (i) the architecture of the NCP+, (ii) two IT-aware aggregation mechanisms to be used in the hierarchical PCE approach and (iii) routing and scheduling algorithms for those aggregation mechanisms. We conclude this work with a thorough simulation analysis of the aggregation and routing/scheduling policies showing that Full Mesh aggregation where the domain topology is represented by a complete graph, although being less scalable in terms of computation time, is able to provision efficiently using the proposed load balancing routing and scheduling policy. However, for a scenario with stringent IT requirements, Star could be used in parallel for scenarios where end-to-end setup times are important.
    Optical Switching and Networking 01/2013; · 0.91 Impact Factor
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    ABSTRACT: Electrical packet switching is well known as a flexible solution for small data transfers, whereas optical flow switching (OFS) might be an effective solution for large Internet file transfers. The UltraFlow project, a joint effort of three universities, Stanford, Massachusetts Institute of Technology, and University of Texas-Dallas, aims at providing an efficient dual-mode solution (i.e., IP and OFS) to the current network. In this paper, we propose and experimentally demonstrate UltraFlow Access, a novel optical access network that enables dual-mode service to the end users: IP and OFS. The new architecture cooperates with legacy passive optical networks (PONs) to provide both IP and novel OFS services. The latter is facilitated by a novel optical flow network unit (OFNU) that we have proposed, designed, and experimentally demonstrated. Different colored and colorless OFNU designs are presented, and their impact on the network performance is explored. Our testbed experiments demonstrate concurrent bidirectional 1.25 Gbps IP and 10 Gbps per-wavelength Flow error-free communication delivered over the same infrastructure. The support of intra-PON OFS communication, that is, between two OFNUs in the same PON, is also explored and experimentally demonstrated.
    Journal of Optical Communications and Networking 01/2013; 5(12):1361-1372. · 1.55 Impact Factor
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    ABSTRACT: Rising energy costs and climate change have led to an increased concern for energy efficiency (EE). As information and communication technology is responsible for about 4% of total energy consumption worldwide, it is essential to devise policies aimed at reducing it. In this paper, we propose a routing and scheduling algorithm for a cloud architecture that targets minimal total energy consumption by enabling switching off unused network and/or information technology (IT) resources, exploiting the cloud-specific anycast principle. A detailed energy model for the entire cloud infrastructure comprising a wide-area optical network and IT resources is provided. This model is used to make a single-step decision on which IT end points to use for a given request, including the routing of the network connection toward these end points. Our simulations quantitatively assess the EE algorithm's potential energy savings but also assess the influence this may have on traditional quality-of-service parameters such as service blocking. Furthermore, we compare the one-step scheduling with traditional scheduling and routing schemes, which calculate the resource provisioning in a two-step approach (selecting first the destination IT end point and subsequently using unicast routing toward it). We show that depending on the offered infrastructure load, our proposed one-step calculation considerably lowers the total energy consumption (reduction up to 50%) compared to the traditional iterative scheduling and routing, especially in low- to medium-load scenarios, without any significant increase in the service blocking.
    Journal of Optical Communications and Networking 01/2013; 5(3):226-239. · 1.55 Impact Factor
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    ABSTRACT: Survivability against disasters-both natural and deliberate attacks, and spanning large geographical areas-is becoming a major challenge in communication networks. Cloud services delivered by datacenter networks yield new opportunities to provide protection against disasters. Cloud services require a network substrate with high capacity, low latency, high availability, and low cost, which can be delivered by optical networks. In such networks, path protection against network failures is generally ensured by providing a backup path to the same destination (i.e., a datacenter), which is link-disjoint to the primary path. This protection fails to protect against disasters covering an area which disrupts both primary and backup paths. Also, protection against destination (datacenter) node failure is not ensured by a generic protection scheme. Moreover, content/service protection is a fundamental problem in a datacenter network, as the failure of a datacenter should not cause the disappearance of a specific content/service from the network. So content placement, routing, and protection of paths and content should be addressed together. In this work, we propose an integrated Integer Linear Program (ILP) to design an optical datacenter network, which solves the above-mentioned problems simultaneously. We show that our disaster protection scheme exploiting anycasting provides more protection, but uses less capacity than dedicated single-link failure protection. We show that a reasonable number of datacenters and selective content replicas with intelligent network design can provide survivability to disasters while supporting user demands. We also propose ILP relaxations and heuristics to solve the problem for large networks.
    Journal of Lightwave Technology 08/2012; 30(16):2563-2573. · 2.86 Impact Factor
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    ABSTRACT: The evolution toward grid and cloud computing as observed for over a decennium illustrates the crucial role played by (optical) networks in supporting today's applications. In this paper, we start from an overview of the challenging applications in both academic (further referred to as scientific), enterprise (business) and nonprofessional user (consumer) domains. They pose novel challenges, calling for efficient interworking of IT resources, for both processing and storage, as well as the network that interconnects them and provides access to their users. We outline those novel applications' requirements, including sheer performance attributes (which will determine the quality as perceived by end users of the cloud applications), as well as the ability to adapt to changing demands (usually referred to as elasticity) and possible failures (i.e., resilience). In outlining the foundational concepts that provide the building blocks for grid/cloud solutions that meet the stringent application requirements we highlight, a prominent role is played by optical networking. The pieces of the solution studied in this respect span the optical transport layer as well as mechanisms located in higher layers (e.g., anycast routing, virtualization) and their interworking (e.g., through appropriate control plane extensions and middleware). Based on this study, we conclude by identifying challenges and research opportunities that can enable future-proof optical cloud systems (e.g., pushing the virtualization paradigms to optical networks).
    Proceedings of the IEEE 05/2012; 100(5):1149-1167. · 5.47 Impact Factor
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    ABSTRACT: Regional failures caused by disasters precipitate huge amount of loss and jeopardize many connections. A risk model for disasters, considering differentiated services, is introduced and a disaster-aware provisioning scheme is proposed to reduce the risk.
    03/2012;
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    ABSTRACT: Orthogonal frequency-division multiplexing (OFDM) is a modulation technology that has been widely adopted in many new and emerging broadband wireless and wireline communication systems. Due to its capability to transmit a high-speed data stream using multiple spectral-overlapped lower-speed subcarriers, OFDM technology offers superior advantages of high spectrum efficiency, robustness against inter-carrier and inter-symbol interference, adaptability to server channel conditions, etc. In recent years, there have been intensive studies on optical OFDM (O-OFDM) transmission technologies, and it is considered a promising technology for future ultra-high-speed optical transmission. Based on O-OFDM technology, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation could be built to support diverse services and the rapid growth of Internet traffic in the future. In this paper, we present a comprehensive survey on OFDM-based elastic optical network technologies, including basic principles of OFDM, O-OFDM technologies, the architectures of OFDM-based elastic core optical networks, and related key enabling technologies. The main advantages and issues of OFDM-based elastic core optical networks that are under research are also discussed.
    IEEE Communications Surveys &amp Tutorials 01/2012; PP(99):1 -23. · 6.49 Impact Factor
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    ABSTRACT: Virtualization of optical networking infrastructure is considered a fundamental technology in the future Internet. A key principle is that virtual networks are isolated to coexist on a shared physical substrate without interference. Although a very attractive proposition for virtual network operators and users, in this paper we demonstrate that realizing complete isolation by partitioning resources is wasteful. Therefore, we propose to group virtual network requests in clusters: within a cluster, bandwidth can be shared, whereas different cluster are properly isolated. Results indicate that intelligent isolation and design of virtual networks can lead to substantial savings of optical network resources compared to a fully isolated approach. Finally, we demonstrate the trade-off between network resource utilization and control plane scalability.
    01/2012;
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    ABSTRACT: In this paper we address the problem of dimensioning infrastructure, comprising both network and server resources, for large-scale decentralized distributed systems such as grids or clouds. We will provide an overview of our work in this area, and in particular focus on how to design the resulting grid/cloud to be resilient against network link and/or server site failures. To this end, we will exploit relocation: under failure conditions, a request may be sent to an alternate destination than the one under failure-free conditions. We will provide a comprehensive overview of related work in this area, and focus in some detail on our own most recent work. The latter comprises a case study where traffic has a known origin, but we assume a degree of freedom as to where its end up being processed, which is typically the case for e.g., grid applications of the bag-of-tasks (BoT) type or for providing cloud services. In particular, we will provide in this paper a new integer linear programming (ILP) formulation to solve the resilient grid/cloud dimensioning problem using failure-dependent backup routes. Our algorithm will simultaneously decide on server and network capacity. We find that in the anycast routing problem we address, the benefit of using failure-dependent (FD) rerouting is limited compared to failure-independent (FID) backup routing. We confirm our earlier findings in terms of network capacity savings achieved by relocation compared to not exploiting relocation (order of 6-10% in the current case studies).
    Communications (ICC), 2012 IEEE International Conference on; 01/2012
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    01/2012;
  • Guoying Zhang, Marc De Leenheer, Biswanath Mukherjee
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    ABSTRACT: Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation technology that transmits a high-speed data stream using multiple spectrally overlapped lower-speed subcarriers. Optical OFDM (O-OFDM) technology is a promising candidate for future high-speed optical transmission. Based on O-OFDM, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation can be built to support diverse services and the rapid growth of Internet traffic. This architecture can provide various services directly at the optical layer in a spectrum-efficient way through bandwidth-elastic optical paths. However, carrying various data rate services using a single type of bandwidth-variable transponder might not be cost-efficient. Electrical traffic grooming is a traditional approach for sub-wavelength service accommodation in wavelength division multiplexing networks. However, it places additional electrical switching and optical-electrical-optical conversion requirements on the network, which may lead to higher cost and energy consumption. In contrast, grooming traffic optically is an attractive option for elastic optical networks. In this paper, we propose a novel optical grooming approach to aggregate and distribute traffic directly at the optical layer in OFDM-based elastic optical networks. We study routing and spectrum allocation algorithms of optical grooming to show the benefits of this approach. Our results demonstrate that significant transmitter and spectrum savings can be achieved by the optical grooming versus the non-grooming scenario, and a trade-off between optimizing the number of transmitters and optimizing spectrum usage should be considered during network planning.
    Journal of Optical Communications and Networking 01/2012; 4(11):B17-B25. · 1.55 Impact Factor
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    ABSTRACT: The last evolutions of the Internet bring the fact that all the emergence of novel applications, requirements, services, roles, and the challenges associated to them is being built on top of the same Internet that was designed for handling completely different elements. Converged, both Information Technology (IT) and optical network, infrastructure resource virtualisation is currently one of the most promising approaches to face the Future Internet challenges. The major research problem associated to infrastructure resource virtualisation is the virtual resource embedding problem. This article presents the grouped Virtual Infrastructure (VI) mapping approach, contextualised within the Generalised Architecture for Dynamic Infrastructure Services (GEYSERS) virtual infrastructure service provisioning framework. Our findings show that batched VI mapping strategy enhances the amount of virtual entities to be allocated on top of the physical substrate. The technological solution presented and the simulation of potential benefits show a novel Information and Communication Technology (ICT) infrastructure control and management solution that is able to accomodate the optimisation requirements for the Future Internet, such as cost, energy, availability, or flexibility, in coordination with application deployments and cloud service models.
    Networks and Optical Communications (NOC), 2012 17th European Conference on; 01/2012
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    ABSTRACT: Quasi-Passive and Reconfigurable (QPAR) optical nodes are implemented using two different discrete optical latching switches based on Micro-Opto-Mechanical and Magneto-Optic principles. A clear trade-off between speed and power consumption is noticed for those QPAR realizations.
    Photonics Conference (IPC), 2012 IEEE; 01/2012
  • Guoying Zhang, M. De Leenheer, B. Mukherjee
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    ABSTRACT: We propose a novel optical grooming approach to aggregate and distribute traffic directly at the optical level in OFDM-based elastic optical networks. Significant transmitter and spectrum saving is achieved compared to non-grooming scenario.
    Optical Fiber Communication Conference and Exposition (OFC/NFOEC), 2012 and the National Fiber Optic Engineers Conference; 01/2012
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    ABSTRACT: Exploiting anycast routing significantly reduces optical network and server energy usage. In this work we present a case study showing that intelligently selecting destinations and routes thereto, while switching off unused (network) elements, cuts power consumption by around 20% and saves network resources by 29%.
    Proceedings of SPIE - The International Society for Optical Engineering 11/2011; · 0.20 Impact Factor
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    ABSTRACT: This paper is aiming at facilitating the energy-efficient operation of an integrated optical network and IT infrastructure. In this context we propose an energy-efficient routing algorithm for provisioning of IT services that originate from specific source sites and which need to be executed by suitable IT resources (e.g. data centers). The routing approach followed is anycast, since the requirement for the IT services is the delivery of results, while the exact location of the execution of the job can be freely chosen. In this scenario, energy efficiency is achieved by identifying the least energy consuming IT and network resources required to support the services, enabling the switching off of any unused network and IT resources. Our results show significant energy savings that can reach up to 55% compared to energy-unaware schemes, depending on the granularity with which a data center is able to switch on/off servers.
    Computer Communications and Networks (ICCCN), 2011 Proceedings of 20th International Conference on; 09/2011
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    J Buysse, M De Leenheer, B Dhoedt, C Develder
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    ABSTRACT: a b s t r a c t Grids use a form of distributed computing to tackle complex computational and data processing prob-lems scientists are presented with today. When designing an (optical) network supporting grids, it is essential that it can overcome single network failures, for which several protection schemes have been devised in the past. In this work, we extend the existing Shared Path protection scheme by incorporating the anycast principle typical of grids: a user typically does not care on what specific server this job gets executed and is merely interested in its timely delivery of results. Therefore, in contrast with Classical Shared Path protection (CSP), we will not necessarily provide a backup path between the source and the original destination. Instead, we allow to relocate the job to another server location if we can thus provide a backup path which comprises less wavelengths than the one CSP would suggest. We assess the bandwidth savings enabled by relocation in a quantitative dimensioning case study on an European and an American network topology, exhibiting substantial savings of the number of required wave-lengths (in the order of 11–50%, depending on network topology and server locations). We also investi-gate how relocation affects the computational load on the execution servers. The case study is based on solving a grid network dimensioning problem: we present Integer Linear Programming (ILP) formulations for both the traditional CSP and the new resilience scheme exploiting relocation (SPR). We also outline a strategy to deal with the anycast principle: assuming we are given just the origins and intensity of job arrivals, we derive a static (source, destination)-based demand matrix. The latter is then used as input to solve the network dimensioning ILP for an optical circuit-switched WDM network.
    Computer Communications 08/2011; 34. · 1.35 Impact Factor

Publication Stats

535 Citations
43.20 Total Impact Points

Institutions

  • 2013
    • Stanford University
      Palo Alto, California, United States
  • 2005–2013
    • Ghent University
      • Department of Information Technology
      Gand, Flanders, Belgium
    • imec Belgium
      Louvain, Flanders, Belgium
  • 2012
    • Concordia University Montreal
      Montréal, Quebec, Canada
  • 2011
    • INTEC
      Belgium, Wisconsin, United States
    • University of California, Davis
      • Department of Computer Science
      Davis, California, United States
    • Universitair Ziekenhuis Ghent
      Gand, Flanders, Belgium
  • 2004–2009
    • University of Essex
      • School of Computer Science and Electronic Engineering
      Colchester, ENG, United Kingdom