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104
Adaptive Wavelength Routing in AllOptical Networks
 IEEE/ACM Transactions on Networking
, 1997
"... In this paper, we consider routing and wavelength assignment in wavelengthrouted alloptical networks with circuitswitching. The conventional approaches to address this issue consider the two aspects of the problem sequentially by first finding a route from a predetermined set of candidate paths an ..."
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Cited by 119 (0 self)
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In this paper, we consider routing and wavelength assignment in wavelengthrouted alloptical networks with circuitswitching. The conventional approaches to address this issue consider the two aspects of the problem sequentially by first finding a route from a predetermined set of candidate paths and then searching for an appropriate wavelength assignment. We adopt a more general approach in which we consider all paths between a sourcedestination pair and incorporate network state information into the routing decision. This approach performs routing and wavelength assignment jointly and adaptively, and outperforms fixed routing techniques. We present adaptive routing and wavelength assignment algorithms and evaluate their blocking performance. We obtain an algorithm to compute approximate blocking probabilities for networks employing fixed and alternate routing techniques. That algorithm can also accommodate networks with multiple fibers per link. The blocking performance of the propo...
Multiwavelength Optical Networks with Limited Wavelength Conversion
, 1997
"... This paper proposes optical wavelength division multiplexed (WDM) networks with limited wavelength conversion that can efficiently support lightpaths (connections) between nodes. Each lightpath follows a route in the network and must be assigned a channel along each link in its route. The load m ..."
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Cited by 82 (3 self)
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This paper proposes optical wavelength division multiplexed (WDM) networks with limited wavelength conversion that can efficiently support lightpaths (connections) between nodes. Each lightpath follows a route in the network and must be assigned a channel along each link in its route. The load max of a set of lightpath requests is the maximum over all links of the number of lightpaths that use the link. At least max wavelengths will be needed to assign channels to the lightpaths. If the network has full wavelength conversion capabilities then max wavelengths are sufficient to perform the channel assignment. We propose ring networks with fixed wavelength conversion capability within the nodes that can support all lightpath request sets with load max at most W \Gamma 1, where W is the number of wavelengths in each link. We also propose ring networks with selective pairwise wavelength conversion capability within the nodes that can support all lightpath request sets with l...
Wavelength conversion in WDM networking
 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
, 1998
"... Wavelength conversion has been proposed for use in wavelengthdivision multiplexed networks to improve efficiency. This study highlights systems challenges and performance issues which need to be addressed in order to incorporate wavelength conversion effectively. A review/survey of the enabling te ..."
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Cited by 78 (3 self)
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Wavelength conversion has been proposed for use in wavelengthdivision multiplexed networks to improve efficiency. This study highlights systems challenges and performance issues which need to be addressed in order to incorporate wavelength conversion effectively. A review/survey of the enabling technologies, design methods, and analytical models used in wavelengthconvertible networks is provided.
Wavelength Assignment in a WDM Ring to Minimize Cost of Embedded SONET Rings
 IN IEEE INFOCOM
, 1998
"... This work deals with wavelength assignment for lightpaths. We restrict our attention to the near term, in which WDM networks will be in the form of rings and higher level networks will be SONET/SDH selfhealing rings. This view changes the goal of wavelength assignment (WLA) vs. previous work on the ..."
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Cited by 76 (1 self)
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This work deals with wavelength assignment for lightpaths. We restrict our attention to the near term, in which WDM networks will be in the form of rings and higher level networks will be SONET/SDH selfhealing rings. This view changes the goal of wavelength assignment (WLA) vs. previous work on the subject in a number of aspects. First, a pair of SONET add/drop multiplexers (ADMs) terminates each lightpath. These ADMs also terminate adjacent lightpaths to form rings, implying that the WLA has to support this type of sharing. Second, following [GRS98], we argue that the firstorder optimization goal should be to minimize the overall network cost which is dominated by the number of required ADMs and not the number of wavelengths. We show that these two minimization problems are intrinsically different, and there exist cases where the two minima cannot be simultaneously achieved. We derive a simple lower bound to the number of ADMs. Depending on the given lightpaths, we show that this lo...
Dynamic Wavelength Routing Using Congestion and Neighborhood Information
 IEEE/ACM TRANSACTIONS ON NETWORKING
, 1999
"... In this paper, we present two dynamic routing algorithms based on path and neighborhood link congestion in alloptical networks. In such networks, a connection request encounters higher blocking probability than in circuitswitched networks because of the wavelength continuity constraint. Much resea ..."
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Cited by 71 (7 self)
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In this paper, we present two dynamic routing algorithms based on path and neighborhood link congestion in alloptical networks. In such networks, a connection request encounters higher blocking probability than in circuitswitched networks because of the wavelength continuity constraint. Much research has focused on the shortestpath routing and alternate shortestpath routing. We consider fixedpaths leastcongestion (FPLC) routing in which the shortest path may not be preferred to use. We then extend the algorithm to develop a new routing method: dynamic routing using neighborhood information. It is shown by using both analysis and simulation methods that FPLC routing with the firstfit wavelength assignment method performs much better than alternate routing method in meshtorus networks (regular topology) and in the NSFnet T1 backbone network (irregular topology). Routing using neighborhood information also achieves good performance when compared to alternate shortestpath routing. ...
Wavelength conversion in optical networks
 Proceedings of 10th ACMSIAM Symposium on Discrete Algorithm (SODA
, 1999
"... In many models of optical routing, we are given a set of communication paths in a network, and we must assign a wavelength to each path so that paths sharing an edge receive dierent wavelengths. The goal is to assign as few wavelengths as possible, in order to make as ecient use as possible of the o ..."
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Cited by 45 (0 self)
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In many models of optical routing, we are given a set of communication paths in a network, and we must assign a wavelength to each path so that paths sharing an edge receive dierent wavelengths. The goal is to assign as few wavelengths as possible, in order to make as ecient use as possible of the optical bandwidth. Much work in the area of optical networks has considered the use of wavelength converters: if a node of a network contains a wavelength converter, any path that passes through this node may change its wavelength. Having converters at some of the nodes can reduce the number of wavelengths required for routing, down to the following natural congestion bound: even with converters, we will always need at least as many wavelengths as the maximum number of paths sharing a single edge. Thus Wilfong and Winkler dened a set S of nodes in a network to be sucient if, placing converters at the nodes in S, every set of paths can be routed with a number of wavelengths equal to its congestion bound. They showed that nding a sucient set of minimum size is NPcomplete, even in planar graphs. In this paper, we provide a polynomialtime algorithm to nd a sucient set for an arbitrary directed network whose size is within a factor of 2 of minimum. We also observe that improving on the factor of 2 would lead to a corresponding improvement for the vertex cover problem. For the case of planar graphs, we provide a polynomialtime approximation scheme. The algorithms are based on connections between the minimum sucient set problem and the undirected feedback vertex set problem. In particular, as a component of the algorithm on planar graphs, we develop the rst polynomialtime approximation scheme for the undirected feedback vertex set problem in planar graphs, a result that we feel to be of interest in its own right. 1
Benefit of Multicasting in AllOptical Networks
, 1998
"... Alloptical WDM networks are fast becoming the natural choice for future backbone. In this paper, we establish the efficiency of multicasting over unicasting in alloptical WDM networks, assess the usefulness of wavelength conversion for multicasting, and explore the issues related to the splitting ..."
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Cited by 44 (3 self)
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Alloptical WDM networks are fast becoming the natural choice for future backbone. In this paper, we establish the efficiency of multicasting over unicasting in alloptical WDM networks, assess the usefulness of wavelength conversion for multicasting, and explore the issues related to the splitting (or copying) capability of the nodes. The comparison between multicasting and unicasting is based on the number of wavelengths as well as the amount of bandwidth required for a given set of multicasting sessions. For each multicasting session, a sourcespecific multicasting forest (or trees) is constructed first, taking into account the sparse splitting capability of the nodes in the network. Then, each multicasting tree is partitioned into segments according to the sparse wavelength conversion capability of the nodes on the tree such that each segment needs to be assigned the same wavelength. Simulation results obtained for a practical network such as NSFNET and randomly generated networks ...
On optimal converter placement in wavelengthrouted networks
 INFOCOM
, 1997
"... Abstract—Wavelength converters increase the trafficcarrying capacity of circuitswitched optical networks by relaxing the wavelength continuity constraints. In this paper, we consider the problem of optimally placing a given number of wavelength converters on a path to minimize the callblocking pr ..."
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Cited by 42 (0 self)
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Abstract—Wavelength converters increase the trafficcarrying capacity of circuitswitched optical networks by relaxing the wavelength continuity constraints. In this paper, we consider the problem of optimally placing a given number of wavelength converters on a path to minimize the callblocking probability. Using a simple performance model, we first prove that uniform spacing of converters is optimal for the endtoend performance when link loads are uniform and independent. We then show that significant gains are achievable with optimal placement compared to random placement. For nonuniform link loads, we provide a dynamic programming algorithm for the optimal placement and compare the performance with random and uniform placement. Optimal solutions for bus and ring topologies are also presented. Finally, we discuss the effect of the traffic model on the placement decision. Index Terms—Call blocking performance, optimal converter placement, sparse wavelength conversion, wavelengthrouting. I.
Routing and wavelength assignment in optical networks
 IEEE/ACM Transactions on Networking
, 2003
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Computing Approximate Blocking Probabilities in Wavelength Routed AllOptical Networks with LimitedRange Wavelength Conversion
, 2000
"... In this paper, we propose a method to calculate the average blocking probability in alloptical networks using limitedrange wavelength conversion. Previous works have shown that there is a remarkable improvement in blocking probability while using limitedrange wavelength conversion, but these anal ..."
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Cited by 38 (0 self)
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In this paper, we propose a method to calculate the average blocking probability in alloptical networks using limitedrange wavelength conversion. Previous works have shown that there is a remarkable improvement in blocking probability while using limitedrange wavelength conversion, but these analytical models were either for a path or for a meshtorus network. Using a graphtheoretical approach, we extend Birman's model for no wavelength conversion and derive an analytical expression to compute the blocking probabilities in networks for fixed routing. The proposed model is applicable to any network topology. We consider the case where an incoming wavelength can be converted to adjacent outgoing wavelengths on either side of the input wavelength, in addition to the input wavelength itself, where is the degree of conversion. When =0and =(( 1) 2), where is the capacity of a link, the proposed model reduces to the model previously given for no wavelength conversion and the model previously given for full wavelength conversion respectively. Using this model we demonstrate that the performance improvement obtained by full wavelength conversion over no wavelength conversion can almost be achieved by using limitedrange wavelength conversion with the degree of conversion, , being only 1 or 2. In a few example networks we considered, for blocking probabilities up to a few percent, the carried traffic with limited conversion degree =2was almost equal to the carried traffic for full wavelength conversion.