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Wolfang Kellerer

Bio: Wolfang Kellerer is an academic researcher from NTT DoCoMo. The author has contributed to research in topics: Competitive analysis & Online algorithm. The author has an hindex of 1, co-authored 1 publications receiving 46 citations.

Papers
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Proceedings ArticleDOI
03 Sep 2010
TL;DR: An optimal offline algorithm based on dynamic programming techniques to find the best migration paths for a given request sequence, and a O(¼ log n)-competitive migration strategy MIG where ¼ is the ratio between maximal and minimal link capacity in the substrate network for a simplified model are presented.
Abstract: Network virtualization promises a high flexibility by decoupling services from the underlying substrate network and allowing the virtual network to adapt to the needs of the service, e.g., by migrating servers or/and parts of the network. We study a system (e.g., a gaming application) where network virtualization is used to support thin client applications for mobile devices to improve their QoS. To deal with the dynamics of both the mobile clients as well as the ability to migrate services closer to the client location we advocate, in this paper, the use of competitive analysis. After identifying the parameters that characterize the cost-benefit tradeoff for this kind of application we propose an online migration strategy. The strength of the strategy is that it is robust with regards to any arbitrary request access pattern. In particular, it is close to the optimal offline algorithm that knows the access pattern in advance.In this paper we present both an optimal offline algorithm based on dynamic programming techniques to find the best migration paths for a given request sequence, and a O(¼ log n)-competitive migration strategy MIG where ¼ is the ratio between maximal and minimal link capacity in the substrate network for a simplified model. This is almost optimal for small ¼, as we also show that there are networks where no online algorithm can achieve a ratio below ©(log n/log log n). In contrast, the optimal solution without migration can only achieve a competitive ratio that is linear in the network diameter. Our simulations indicate that the competitive ratio of MIG is robust to the network size, and that the ratio is small if the request dynamics are limited and the requests are correlated.

46 citations


Cited by
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Journal ArticleDOI
TL;DR: A survey of current research in the Virtual Network Embedding (VNE) area is presented and a taxonomy of current approaches to the VNE problem is provided and opportunities for further research are discussed.
Abstract: Network virtualization is recognized as an enabling technology for the future Internet. It aims to overcome the resistance of the current Internet to architectural change. Application of this technology relies on algorithms that can instantiate virtualized networks on a substrate infrastructure, optimizing the layout for service-relevant metrics. This class of algorithms is commonly known as "Virtual Network Embedding (VNE)" algorithms. This paper presents a survey of current research in the VNE area. Based upon a novel classification scheme for VNE algorithms a taxonomy of current approaches to the VNE problem is provided and opportunities for further research are discussed.

1,174 citations

Journal ArticleDOI
TL;DR: Previous work on, and the present status of, resource discovery and allocation in network virtualization are surveyed and challenges are described and future directions for this area of research are suggested.
Abstract: Network virtualization is considered an important potential solution to the gradual ossification of the Internet. In a network virtualization environment, a set of virtual networks share the resources of a common physical network although each virtual network is isolated from others. Benefits include increased flexibility, diversity, security and manageability. Resource discovery and allocation are fundamental steps in the process of creating new virtual networks. This paper surveys previous work on, and the present status of, resource discovery and allocation in network virtualization. We also describe challenges and suggest future directions for this area of research.

185 citations

Journal ArticleDOI
TL;DR: An opportunistic resource sharing-based mapping framework, ORS, where substrate resources are opportunistically shared among multiple virtual networks, and it is proved that ORS provides a more efficient utilization of substrate resources than two state-of-the-art fixed-resource embedding schemes.
Abstract: Network virtualization has emerged as a promising approach to overcome the ossification of the Internet. A major challenge in network virtualization is the so-called virtual network embedding problem, which deals with the efficient embedding of virtual networks with resource constraints into a shared substrate network. A number of heuristics have been proposed to cope with the NP-hardness of this problem; however, all of the existing proposals reserve fixed resources throughout the entire lifetime of a virtual network. In this paper, we re-examine this problem with the position that time-varying resource requirements of virtual networks should be taken into consideration, and we present an opportunistic resource sharing-based mapping framework, ORS, where substrate resources are opportunistically shared among multiple virtual networks. We formulate the time slot assignment as an optimization problem; then, we prove the decision version of the problem to be NP-hard in the strong sense. Observing the resemblance between our problem and the bin packing problem, we adopt the core idea of first-fit and propose two practical solutions: first-fit by collision probability (CFF) and first-fit by expectation of indicators' sum (EFF). Simulation results show that ORS provides a more efficient utilization of substrate resources than two state-of-the-art fixed-resource embedding schemes.

108 citations

Journal ArticleDOI
TL;DR: This paper addresses the issue of how to optimally reconfigure and map an existing VN while the VN request changes, and model this problem as a mathematical optimization problem with the objective of minimizing the reconfiguration cost by using mixed integer linear programming.

86 citations

Journal ArticleDOI
TL;DR: A service placement architecture for the Internet of Things is proposed, with especial emphasis in its main module, the Service Orchestrator, for which implementation details are provided, including a model for the service placement task.
Abstract: New services and applications become part of our daily activities as we evolve into new solutions supported by cutting-edge paradigms, like the Internet of Things and Smart Cities. In order to properly achieve the benefits theoretically provided by these models, new kinds of services must be designed. These new services have special requirements, as well as the users that access to them. One of these requirements is low latency levels, since a delayed reply could render to chaos for applications such as eHealth and public safety. The communication infrastructure must cope with these challenges by offering innovative solutions. One of these solutions is a smart service placement system that facilitates the location of services in the proper position according to specific needs. On this paper, a service placement architecture for the Internet of Things is proposed, with especial emphasis in its main module, the Service Orchestrator, for which implementation details are provided, including a model for the service placement task. Furthermore, technologies to implement the modules from the architecture are suggested. This proposal, as well as its validation, is framed within the scope of the SusCity project.

66 citations