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147
On Optimal Traffic Grooming in WDM Rings
 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
, 2002
"... We consider the problem of designing a virtual topology to minimize electronic routing, that is, grooming traffic, in wavelength routed optical rings. The full virtual topology design problem is NPhard even in the restricted case where the physical topology is a ring, and various heuristics have be ..."
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Cited by 66 (19 self)
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We consider the problem of designing a virtual topology to minimize electronic routing, that is, grooming traffic, in wavelength routed optical rings. The full virtual topology design problem is NPhard even in the restricted case where the physical topology is a ring, and various heuristics have been proposed in the literature for obtaining good solutions, usually for different classes of problem instances. We present a new framework which can be used to evaluate the performance of heuristics and which requires significantly less computation than evaluating the optimal solution. This framework is based on a general formulation of the virtual topology problem, and it consists of a sequence of bounds, both upper and lower, in which each successive bound is at least as strong as the previous one. The successive bounds take larger amounts of computation to evaluate, and the number of bounds to be evaluated for a given problem instance is only limited by the computational power available. The bounds are based on decomposing the ring into sets of nodes arranged in a path and adopting the locally optimal topology within each set. While we only consider the objective of minimizing electronic routing in this paper, our approach to obtaining the sequence of bounds can be applied to many virtual topology problems on rings. The upper bounds we obtain also provide a useful series of heuristic solutions.
Virtualtopology adaptation for WDM mesh networks under dynamic traffic
 IEEE/ACM Transactions on Networking
, 2002
"... Abstract — We present a new approach to the virtualtopology reconfiguration problem for wavelengthrouted, optical widearea networks under dynamic traffic demand. By utilizing the measured Internet backbone traffic characteristics, an adaptation mechanism is proposed to follow the changes in traff ..."
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Cited by 58 (0 self)
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Abstract — We present a new approach to the virtualtopology reconfiguration problem for wavelengthrouted, optical widearea networks under dynamic traffic demand. By utilizing the measured Internet backbone traffic characteristics, an adaptation mechanism is proposed to follow the changes in traffic without assuming that the future traffic pattern is known. In that sense, our work differs from the previous studies which redesign the virtualtopology according to an expected (or known) traffic pattern, and then modify the connectivity to reach the target topology. The key idea of our approach is to adapt the underlying optical connectivity by measuring the actual traffic load on lightpaths continuously (periodically based on a measurement period) and reacting promptly to the imbalances caused by fluctuations on the traffic by adding or deleting one lightpath at a time. We aim to correct the encountered load imbalance directly, either by tearing down a lightpath that is lightly loaded or by setting up a new lightpath when congestion occurs. We introduce high and low watermark parameters on lightpath loads to detect any over/underutilized lightpath, and to trigger an adaptation step. The adaptation method is evaluated through simulations and the effect of system parameters (high and low watermarks, length of the measurement period) are investigated. I.
Algorithm for Traffic Grooming in Optical Networks to Minimize the Number of Transceivers
 Major Indices for the Hyperoctahedral Group, Manuscript
, 2001
"... In this paper, we study the problem of traffic grooming to reduce the number of transceivers in optical networks. We show that this problem is equivalent to a certain traffic maximization problem. We give an intuitive interpretation of this equivalence and use this interpretation to derive a greedy ..."
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Cited by 49 (0 self)
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In this paper, we study the problem of traffic grooming to reduce the number of transceivers in optical networks. We show that this problem is equivalent to a certain traffic maximization problem. We give an intuitive interpretation of this equivalence and use this interpretation to derive a greedy algorithm for transceiver minimization. We discuss implementation issues and present computational results comparing the heuristic solutions with the optimal solutions for several small example networks. For larger networks, the heuristic solutions are compared with known bounds on the optimal solution obtained using integer programming tools.
Traffic Grooming in Path, Star, and Tree Networks: Complexity Bounds and Algorithms
, 2004
"... We consider the problem of traffic grooming in WDM path, star, and tree networks. Traffic grooming is a variant of the wellknown logical topology design, and is concerned with the development of techniques for combining low speed traffic components onto high speed channels in order to minimize netw ..."
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Cited by 40 (12 self)
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We consider the problem of traffic grooming in WDM path, star, and tree networks. Traffic grooming is a variant of the wellknown logical topology design, and is concerned with the development of techniques for combining low speed traffic components onto high speed channels in order to minimize network cost. Our contribution is twofold. In the first part of the paper we present a wealth of results which settle the complexity of traffic grooming in path and star networks, by proving that a number of variants of the problem are computationally intractable. Since routing and wavelength assignment in these two topologies is trivial, these results demonstrate that traffic grooming is itself an inherently difficult problem. Our results have implications for ring and other more general topologies, which we explore. In the second part, we design practical grooming algorithms with provable properties. Specifically, for all three topologies, we obtain a series of lower and upper bounds which are increasingly tighter but have considerably higher computational requirements; the series of upper bounds forms an algorithm for the traffic grooming problem with strong performance guarantees. We also present corresponding heuristics with good performance. Our work is a first step towards a formal and systematic approach to the grooming problem in general topologies that builds upon results and algorithms for more elementary networks.
Traffic Grooming in Unidirectional WDM Ring Networks Using Design Theory
 IN IEEE ICC
, 2003
"... We address the problem of traffic grooming in WDM rings with alltoall uniform unitary traffic. We want to minimize the total number of SONET adddrop multiplexers (ADMs) required. We show that this problem corresponds to a partition of the edges of the complete graph into subgraphs, where each s ..."
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Cited by 35 (9 self)
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We address the problem of traffic grooming in WDM rings with alltoall uniform unitary traffic. We want to minimize the total number of SONET adddrop multiplexers (ADMs) required. We show that this problem corresponds to a partition of the edges of the complete graph into subgraphs, where each subgraph has at most C edges (where C is the grooming ratio) and where the total number of vertices has to be minimized. Using tools of graph and design theory, we optimally solve the problem for practical values and infinite congruence classes of values for a given C, and thus improve and unify all the preceding results. We disprove a conjecture of [7] saying that the minimum number of ADMs cannot be achieved with the minimum number of wavelengths, and also another conjecture of [17].
Routing and Wavelength Assignment in Optical WDM Networks
, 2001
"... This article discusses the routing and wavelength assignment (RWA) problem in optical networks employing wavelenength division multiplexing (WDM) technology. Two variants of the problem are studied: static RWA, whereby the tra#c requirements are known in advance, and dynamic RWA in which connecti ..."
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Cited by 18 (4 self)
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This article discusses the routing and wavelength assignment (RWA) problem in optical networks employing wavelenength division multiplexing (WDM) technology. Two variants of the problem are studied: static RWA, whereby the tra#c requirements are known in advance, and dynamic RWA in which connection requests arrive in some random fashion. Both pointtopoint and multicast tra#c demands are considered.
Transparent optical network design with sparse wavelength conversion
, 2002
"... We consider the design of transparent optical networks from a practical perspective. Network operators aim at satisfying the communication demands at minimum cost. Such an optimization involves three interdependent planning issues: the dimensioning of the physical topology, the routing of lightpath ..."
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Cited by 17 (4 self)
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We consider the design of transparent optical networks from a practical perspective. Network operators aim at satisfying the communication demands at minimum cost. Such an optimization involves three interdependent planning issues: the dimensioning of the physical topology, the routing of lightpaths, and the wavelength assignment. Further topics include the reliability of the configuration and sparse wavelength conversion for efficient use of the capacities. In this paper, we investigate this extensive optical network design task. Using a flexible devicebased model, we present an integer programming formulation that supports greenfield planning as well as expansion planning on top of an existing network. As solution method, we propose a suitable decomposition approach that separates the wavelength assignment from the dimensioning and routing. Our method in particular provides a lower bound on the total cost which allows to rate the solution quality. Computational experiments on realistic networks approve the solution approach to be appropriate.
Traffic Grooming on the Path
"... In a WDM network, routing a request consists in assigning it a route in the physical network and a wavelength. If each request uses at most 1/C of the bandwidth of the wavelength, we will say that the grooming factor is C. That means that on a given edge of the network we can groom (group) at most C ..."
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Cited by 14 (6 self)
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In a WDM network, routing a request consists in assigning it a route in the physical network and a wavelength. If each request uses at most 1/C of the bandwidth of the wavelength, we will say that the grooming factor is C. That means that on a given edge of the network we can groom (group) at most C requests on the same wavelength. With this constraint the objective can be either to minimize the number of wavelengths (related to the transmission cost) or minimize the number of Add Drop Multiplexers (shortly ADM) used in the network (related to the cost of the nodes). We consider here the case where the network is a path on N nodes, PN. Thus the routing is unique. For a given grooming factor C minimizing the number of wavelengths is an easy problem, well known and related to the load problem. But minimizing the number of ADM’s is NPcomplete for a general set of requests and no results are known. Here we show how to model the problem as a graph partition problem and using tools of design theory we completely solve the case where C = 2 and where we have a static uniform alltoall traffic (one request for each pair of vertices).
On the Physical and Logical Topology Design of LargeScale Optical Networks
 JOURNAL OF LIGHTWAVE TECHNOLOGY
, 2003
"... We consider the problem of designing a network of optical crossconnects (OXCs) to provide endtoend lightpath services to large numbers of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined problem of physical topology design (i.e., determine the number ..."
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Cited by 13 (1 self)
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We consider the problem of designing a network of optical crossconnects (OXCs) to provide endtoend lightpath services to large numbers of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined problem of physical topology design (i.e., determine the number of OXCs required and the fiber links among them) and logical topology design (i.e., determine the routing and wavelength assignment for the lightpaths among the LSRs). Unlike previous studies which were limited to small topologies with a handful of nodes and a few tens of lightpaths, we have applied our algorithms to networks with hundreds or thousands of LSRs and with a number of lightpaths that is an order of magnitude larger than the number of LSRs. In order to characterize the performance of our algorithms, we have developed lower bounds which can be computed efficiently. We present numerical results for up to 1000 LSRs and for a wide range of system parameters such as the number of wavelengths per fiber, the number of transceivers per LSR, and the number of ports per OXC. The results indicate that it is possible to build largescale optical networks with rich connectivity in a costeffective manner, using relatively few but properly dimensioned OXCs.
Challenges for the NextGeneration Internet and The Role of IP over Photonic Networks
, 2000
"... this article, we first discuss QoS metrics of the data networks, followed by raising the challenging problems for the nextgeneration Internet with highperformance and highquality. We then discuss how the WDM technology can be incorporated for resolving those problems. Several research issues f ..."
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Cited by 11 (8 self)
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this article, we first discuss QoS metrics of the data networks, followed by raising the challenging problems for the nextgeneration Internet with highperformance and highquality. We then discuss how the WDM technology can be incorporated for resolving those problems. Several research issues for the IP over WDM networks are also identified