| 1. |
- Pioro, Michal, et al.
(author)
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Elastic Multi-Layer Resilient IP-over-Flexgrid Networking: Detailed Cost Analysis with Bandwidth-Variable Transponders
- 2014
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In: [Host publication title missing].
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Conference paper (peer-reviewed)abstract
- We introduce a mixed-integer optimization model for two-layer IP-over-Flexgrid networks, and present a cost study performed using the CPLEX package for the introduced model. The study concerns a generic German network with 12 nodes and 20 links in the optical layer, and a set of six IP traffic matrices with increasing demand volumes. The optimization assumes a hot-standby mechanism in the optical layer to make the network resilient to cable cuts. The dominant cost drivers are bandwidth-variable transponders. The numerical results reveal that due to the huge spectral capacity of a single fiber, the spectrum allocation problem simplifies significantly in practice. However, the routing problem minimizing the total cost of employed transponders becomes a challenge, but when appropriately approached and solved, can bring reductions in costs of up to 10%.
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| 2. |
- Klinkowski, M., et al.
(author)
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Valid Inequalities for the Routing and Spectrum Allocation Problem in Elastic Optical Networks
- 2014
-
In: [Host publication title missing].
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Conference paper (peer-reviewed)abstract
- We deal with a natural integer-linear programming formulation of the routing and spectrum allocation (RSA) problem in elastic optical networks. We focus on strengthening the formulation with valid inequalities (cuts). For this purpose we apply clique inequalities that proved to be useful in other applications of this kind. We develop and combine a clique cut generation procedure with a column generation algorithm with the aim to improve the quality of generated columns. The presented results, obtained for a set of problem instances, illustrate the effectiveness of the optimization algorithm.
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| 3. |
- Ruiz, M., et al.
(author)
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After failure repair optimization in dynamic flexgrid optical networks
- 2014
-
In: [Host publication title missing]. - 9781557529947
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Conference paper (peer-reviewed)abstract
- We introduce the problem of reoptimizing the network after a link failure has been repaired as an effective way for reducing capacity usage and improving network performance. Numerical results show gains higher than 42%.
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| 4. |
- Zotkiewicz, M., et al.
(author)
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Optimization models for flexgrid elastic optical networks
- 2013
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In: [Host publication title missing]. - 2161-2056.
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Conference paper (peer-reviewed)abstract
- In the paper we present integer programming (IP) optimization models for flexgrid elastic optical networks (EON). We consider several different basic assumptions regarding flexibility of EON that lead to a variety of IP formulations differing in precision and complexity. As usual, detailed models aiming at precisely describing technological aspects of EON suffer from tractability issues resulting from their greater complexity and have to be reasonably simplified. To achieve this, we consider cases where the bandwidth is divided into predefined slots, cases where the bandwidth is continuous and can be divided between demands with no restrictions, cases where a list of predefined paths is available, and finally cases where all the paths are indirectly taken into account. We present both compact and non-compact formulations. The non-compact formulations are accompanied with brief description of the dedicated column generation algorithms.
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| 5. |
- Zotkiewicz, M., et al.
(author)
-
Reoptimization of Dynamic Flexgrid Optical Networks After Link Failure Repairs
- 2015
-
In: Journal of Optical Communications and Networking. - 1943-0639. ; 7:1
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Journal article (peer-reviewed)abstract
- In dynamic flexgrid optical networks, the usage of capacity may not be optimal due to the permanent process of setting up and tearing down connections, which, if not controlled, leads to spectrum fragmentation and, as a result, to increase of connection blocking. On top of this, a restoration mechanism that is launched in reaction to a link failure (cable cut) restores the affected lightpaths. Eventually, when the cable is repaired and its capacity becomes available for new connections, the unbalance between lightly and heavily loaded links increases, thus further decreasing the probability of finding optical paths with continuous and contiguous spectrum for future connection requests. In this paper we study the effects of reoptimizing the lightpath connections after a link failure has been repaired [namely, the after-failure-repair optimization (AFRO) problem] as an effective way for both reducing and balancing capacity usage and, by these means, for improving network performance. To solve AFRO a column generation decomposition method is presented. Illustrative numerical results show that AFRO allows us to significantly decrease the request blocking probability in realistic dynamic network scenarios. Moreover, the proposed column generation algorithm delivers quasi-optimal solutions in reasonable times. Besides, traffic disruptions resulting from lightpath rerouting are practically negligible. Finally, we show that it is sufficient to apply AFRO only for a selected set of link failures in order to achieve high network performance.
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| 6. |
- Callegati, F., et al.
(author)
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Research on Optical Core Networks in the e-Photon/ONe Network of Excellence
- 2006
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In: 25TH IEEE INTERNATIONAL CONFERENCE ON COMPUTER COMMUNICATIONS, VOLS 1-7, PROCEEDINGS IEEE INFOCOM 2006. ; , s. 2987-2991
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Conference paper (peer-reviewed)abstract
- This papers reports the advances in optical core networks research coordinated in the framework of the e- photon/ONe and e-photon/ONe+ networks of excellence.
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| 7. |
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| 8. |
- Klinkowski, M, et al.
(author)
-
Routing optimization in optical burst switching networks: a multi-path routing approach
- 2009
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In: Graphs and algorithms in communication networks – studies in broadband, optical, wireless, and Ad Hoc networks. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642022494 ; , s. 163-178
-
Book chapter (peer-reviewed)abstract
- This chapter concerns routing optimization in optical burst switching (OBS) networks. OBS is a photonic network technology aiming at efficient transport of IP traffic. OBS architectures are in general bufferless and therefore sensitive to burst congestion. An overall burst loss probability (BLP) which adequately represents the congestion state of the entire network is the primary metric of interest in an OBS network. The network congestion can be reduced by using proper routing. We consider multi-path source routing and aim at optimal distribution of traffic over the network. In this context, we study three network loss models, a well-known loss model of an OBS network and two original approximate models. Since the objective function of each model is nonlinear, either linear programming formulations with piecewise linear approximations of this function or nonlinear optimization gradient methods can be used. The presented solution is based on nonlinear optimization; for this purpose we provide the formulas for calculation of partial derivatives. The main goal of this chapter is to show that the use of approximate models allows us to speed up significantly the optimization procedure without losing much accuracy. Moreover we show that our method effectively distributes the traffic over the network, and the overall BLP can be reduced compared with both shortest path routing and alternative routing.
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| 9. |
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| 10. |
- Klinkowski, M., et al.
(author)
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Virtual Topology Design in OBS Networks
- 2010
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In: [Host publication title missing]. - 9781424477999
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Conference paper (peer-reviewed)abstract
- The problem of burst losses in OBS networks has an impact on the service quality perceived by end users. In order to guarantee certain level of Service Quality (QoS) in terms of burst losses, wavelength resources have to be dimensioned properly. In this paper, we address the problem of the Virtual Topology (VT) design that concerns the establishment of explicit routing paths and the allocation of wavelengths in network links to support connections with QoS guarantees in the OBS network. We consider the GMPLS control plane as an overlying technology which facilitates the establishment of VT on top of physical network topology.
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