Marc De Leenheer

INTEC, Belgium, Wisconsin, United States

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Publications (76)21.65 Total impact

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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; · 1.27 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. · 1.43 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; · 0.72 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. · 2.56 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.
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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.
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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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    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 01/2012; 100(5):1149-1167. · 6.91 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: 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%.
    Proc SPIE 11/2011;
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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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    ABSTRACT: Grids can efficiently deal with challenging computational and data processing tasks which cutting edge science is generating today. So-called e-Science grids cope with these complex task by deploying geographically distributed server infrastructure, interconnected by high speed networks. The latter benefit from optical technology, offering low latencies and high bandwidths, thus giving rise to so-called optical grids or lambda grids. In this paper, we address the dimensioning problem of such grids: how to decide how much server infrastructure to deploy, at which locations in a given topology, the amount of network capacity to provide and which routes to follow along them. Compared to earlier work, we propose an integrated solution solving these questions in an integrated way, i.e., we jointly optimize network and server capacity, and incorporate resiliency against both network and server failures. Assuming we are given the amount of resource reservation requests arriving at each network node (where a resource reservation implies to reserve both processing capacity at a server site, and a network connection towards it), we solve the problem of first choosing a predetermined number of server locations to use, and subsequently determine the routes to follow while minimizing resource requirements. In a case study on a meshed European network comprising 28 nodes and 41 links, we show that compared to classical (i.e. without relocation) shared path protection against link failures only, we can offer resilience against both single link and network failures by adding about 55% extra server capacity, and 26% extra wavelengths.
    Communications (ICC), 2011 IEEE International Conference on; 07/2011
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    ABSTRACT: In this paper we propose energy efficient design and operation of infrastructures incorporating integrated optical network and IT resources. For the first time we quantify significant energy savings of a complete solution jointly optimizing the allocation and provisioning of both network and IT resources. Our approach involves virtualization of the infrastructure resources and it is proposed and developed in the framework of the European project GEYSERS - Generalised Architecture for Dynamic Infrastructure Services.
    Computer Communications Workshops (INFOCOM WKSHPS), 2011 IEEE Conference on; 05/2011
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    ABSTRACT: Network virtualization has been proposed as a key enabler of the future internet, as it allows multiple networks to coexist on a shared physical infrastructure, and as such overcomes the difficulties in deploying novel technologies in the current Internet. However, much confusion still exists on the impact virtualization will have on performance, since we lack the necessary tools to study the behaviour of a virtualized network infrastructure. We report on the architecture and implementation of a simulation environment for virtualizing both (optical) network and IT infrastructures. We provide a detailed overview of the layered architecture, give insight in the design and implementation of the simulator, discuss potential use cases and finally include some preliminary results.
  • Computer Communications Workshops (INFOCOM WKSHPS), 2011 IEEE Conference on; 01/2011
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    ABSTRACT: GEYSERS aims at defining an end-to-end network architecture that offers a novel planning, provisioning and operational framework for optical network and IT infrastructure providers and operators. In this framework, physical infrastructure resources (network and IT) are dynamically partitioned to virtual resources and then composed into a Virtual Infrastructure offered to operators as a service. The operator will be able to operate a virtual infrastructure with an enhanced Network Control Plane (NCP) able to offer coupled, optimized and dynamic on-demand Network and IT provisioning services (i.e., interconnections between multiple IT resources and end-users). The scope and novelty of the GEYSERS architecture is focused on the functional definition and description of two innovative layers, the enhanced Network Control Plane (NCP) and the Logical Infrastructure Composition Layer (LICL). The Service Middleware Layer (SML) and the physical layer (PHY) are part of the overall GEYSERS architecture but are based on existing developments that will be appropriately adapted or extended.
    Future Network & Mobile Summit (FutureNetw), 2011; 01/2011
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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. 01/2011; 34.
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    ABSTRACT: The European Integrated Project GEYSERS - Generalised Architecture for Dynamic Infrastructure Services - is concentrating on infrastructures incorporating integrated optical network and IT resources in support of the Future Internet with special emphasis on cloud computing. More specifically GEYSERS proposes the concept of Virtual Infrastructures over one or more interconnected Physical Infrastructures comprising both network and IT resources. Taking into consideration the energy consumption levels associated with the ICT today and the expansion of the Internet in size and complexity, that incurring increased energy consumption of both IT and network resources, energy efficient infrastructure design becomes critical. To address this need, in the framework of GEYSERS, we propose energy efficient design of infrastructures incorporating integrated optical network and IT resources, supporting resilient end-to-end services. Our modeling results quantify significant energy savings of the proposed solution by jointly optimizing the allocation of both network and IT resources.
    Transparent Optical Networks (ICTON), 2011 13th International Conference on; 01/2011
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    ABSTRACT: By utilizing Layer-1 Virtual Private Networks (L1VPN), a single physical network, e.g., an optical backbone network, can support multiple virtual networks, which form the basic infrastructure for cloud computing and other enterprise networks. The L1VPN hose model is an elegant and flexible way to specify the customers’ bandwidth requirements, by defining the total incoming and outgoing demand for each endpoint. Furthermore, multi-domain physical infrastructures are common in L1VPNs, since these are usually deployed on a global scale. Thus, high-performance Routing for Multi-domain VPN Provisioning (RMVP) for the hose model is an important problem to efficiently support a global virtual infrastructure. In this paper, we formulate the RMVP problem as a Mixed Integer Linear Program (MILP). Also, we propose a Top-Down Routing (TDR) strategy to compute the optimal routing for the hose model L1VPN in a multi-domain backbone network. Results indicate that TDR approaches the minimum routing cost when compared to the ideal case of single-domain routing.
    Proceedings of the 12th IEEE International Conference on High Performance Switching and Routing, HPSR 2011, 4-6 July 2011, Cartagena, Spain; 01/2011

Publication Stats

281 Citations
21.65 Total Impact Points


  • 2011
    • INTEC
      Belgium, Wisconsin, United States
    • University of California, Davis
      • Department of Electrical and Computer Engineering
      Davis, CA, United States
    • Universitair Ziekenhuis Ghent
      Gand, Flanders, Belgium
  • 2004–2011
    • Ghent University
      • Department of Information Technology
      Gent, VLG, Belgium
  • 2004–2009
    • University of Essex
      • School of Computer Science and Electronic Engineering
      Colchester, ENG, United Kingdom
  • 2005
    • imec Belgium
      Louvain, Flanders, Belgium