by Kubilinskas, Eligijus; Nilsson, Pål; Pióro, Michał

This paper presents three mathematical formulations for designing robust two-layer networks carrying elastic traffic. The formulations differ in the way flow reconfiguration is performed in the case of link failures. An iterative algorithm to solve the problems is given and a numerical study is provided comparing the effectiveness of the three reconfiguration mechanisms. The formulations can be applied for designing Next Generation Internet (NGI) core networks with the two-layer, IP-over-WDM, structure.

DOI: 10.1007/s10922-005-1859-0
Print publication date: 3/1/2005
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by Al-Naamany, A. M.; Bourdoucen, H.

With the continuous increasing demand of Internet applications, networks are experiencing a serious congestion problem. This affects directly the networks’ services and management due to large amounts of data loss and long transmission delays. The present work suggests an improved networking congestion control approach for TCP using fuzzy logic. Its main objective is to use packet drop information to improve network services by optimizing data throughput and smoothing data transfer profiles.

DOI: 10.1007/s10922-005-1843-8
Print publication date: 3/1/2005
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by Grover, Wayne; Tipper, David

DOI: 10.1007/s10922-005-1844-7
Print publication date: 3/1/2005
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by Gupta, Rajarshi; Chi, Eric; Walrand, Jean

Many network routing situations commonly require backup paths that satisfy various constraints on bandwidth, link or node selection, and ease of configuration. In this paper, we attempt to validate whether it is beneficial to have distinct algorithmic treatments of normal and backup path calculation, configuration, and maintenance. We present a modular suite of algorithms that enable us to manage normal and protection paths differently. In the process, we develop a simple extension of Minimum Interference Routing Algorithm for shared protection paths. We incorporate a distributed algorithm to separately calculate normal and backup paths in the network, using link state information, and present an evaluation of asynchronous dynamic reorganization of backup paths to reduce congestion in the network. Simulations demonstrate nontrivial quantitative reductions in blocking probabilities under certain conditions. We conclude that in order to choose an optimal algorithm for a protected QoS routing application, it is recommended to also consider a combination of two different algorithms for normal and backup paths.

DOI: 10.1007/s10922-005-1845-6
Print publication date: 3/1/2005
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by Koster, Arie M. C. A.; Zymolka, Adrian; Jäger, Monika; Hülsermann2, Ralf

In this paper, a new shared protection mechanism for meshed optical networks is presented. Significant network design cost reductions can be achieved in comparison to the well-known 1+1 protection scheme. Demand-wise Shared Protection (DSP) is based on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of protection. Computational experiments illustrate the benefits of the DSP concept for cost efficient optical network designs.

DOI: 10.1007/s10922-005-1855-4
Print publication date: 3/1/2005
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by Mobiot, Florent; Sansò, Brunilde; Girard, André

The increased bandwidth demand for new Internet applications suggests mapping IP directly over the wavelength-division multiplexing (WDM) layer. Since reliability is such a critical issue in these broadband networks, we propose an integrated design method which addresses the problem of survivability as viewed from the IP/MPLS layers but taking into account the failure mechanisms in the optical layer. This approach is becoming practical because of the emergence of generalized multiprotocol label switching (GMPLS) as a multilayer control plane that can support the signaling required for coordinating the restoration mechanisms in multiple layers.The model relies on network calculus to evaluate a quality of service (QoS) metric as actually perceived by end users and computes a preplanned restoration scheme to recover from failures. We discuss the numerical implementation, the convergence and the solutions produced by the algorithm and show that the resulting network can provide the prescribed QoS guarantees for all failure states.

DOI: 10.1007/s10922-005-1862-5
Print publication date: 3/1/2005
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by Orlowski, Sebastian; Wessäly, Roland

We investigate the impact of link and path restoration on the cost of telecommunication networks. The main observation is that the cost of an optimal network configuration is almost independent of the restoration concept if (i) the installation of network elements (ADMs, DXCs, or routers) and interface cards, (ii) link capacities, and (iii) working and restoration routings are simultaneously optimized.We present a mixed-integer programming model which integrates all these decisions. Using a branch-and-cut algorithm (with column generation to deal with all admissible routing paths), we solve structurally different real-world based problem instances and show that the cost of optimal solutions is almost independent of the used restoration concept.In addition, we optimize spare capacities based on predetermined shortest working paths with respect to different link weights. On our test instances, the additional cost of solutions obtained with this sequential approach, compared to simultaneous optimization of working and restoration routings, varies between 0 and 164%.

DOI: 10.1007/s10922-005-1864-3
Print publication date: 3/1/2005
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by Hegyi, Péter; Maliosz, Markosz; Ladányi, Ákos; Cinkler, Tibor

In this paper different algorithms are presented and evaluated for designing Virtual Private/Overlay Network (VPNs/VONs) over any network that supports resource partitioning e.g. ATM (Asynchronous Transfer Mode), MPLS (Multi Protocol Label Switching), or SDH/SONET (Synchronous Digital Hierarchy/Synchronous Optical Networking). All algorithms incorporate protection as well. The VPNs/VONs are formed by full mesh demand sets between VPN/VON endpoints. The service demands of VPNs/VONs are characterized by the bandwidth requirements of node-pairs (pipe-model).We investigated four design modes with three pro-active path based shared protection path algorithms and four heuristics to calculate the pairs of paths. The design mode determines the means of traffic concentration. The protection path algorithms use Dijkstra’s shortest path calculation with different edge weights. The demands are routed one-by-one, therefore the order in which they are processed matters.To eliminate this factor we used three heuristics (simulated allocation, simulated annealing, threshold accepting). We present numerical results obtained by simulation regarding the required total amount of capacity, the number of reserved edges, and the average length of paths.

DOI: 10.1007/s10922-005-1865-2
Print publication date: 3/1/2005
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DOI: 10.1007/s10922-005-4562-2
Print publication date: 3/1/2005
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