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148
Traffic grooming in an optical WDM mesh network
 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
, 2002
"... In wavelengthdivision multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming lowspeed connections onto highcapacity lightpaths will improve the network throughput and reduce the network cost. In WDM/S ..."
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Cited by 159 (10 self)
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In wavelengthdivision multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming lowspeed connections onto highcapacity lightpaths will improve the network throughput and reduce the network cost. In WDM/SONET ring networks, it has been shown in the optical network literature that by carefully grooming the lowspeed connection and using wavelengthdivision multiplexer (OADM) to perform the optical bypass at intermediate nodes, electronic ADMs can be saved and network cost will be reduced. In this study, we investigate the trafficgrooming problem in a WDMbased optical mesh topology network. Our objective is to improve the network throughput. We study the node architecture for a WDM mesh network with trafficgrooming capability. A mathematical formulation of the trafficgrooming problem is presented in this study and several fast heuristics are also proposed and evaluated.
A Survey of Virtual Topology Design Algorithms for Wavelength Routed Optical Networks
 Optical Networks
, 2000
"... In the past few years, there has been growing interest in wide area "All Optical Networks" with wavelength division multiplexing (WDM), using wavelength routing. Due to the huge bandwidth inherent in optical fiber, and the use of WDM to match user and network bandwidths, the wavelength ..."
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Cited by 153 (12 self)
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In the past few years, there has been growing interest in wide area "All Optical Networks" with wavelength division multiplexing (WDM), using wavelength routing. Due to the huge bandwidth inherent in optical fiber, and the use of WDM to match user and network bandwidths, the wavelength routing architecture is an attractive candidate for future backbone transport networks. A virtual topology over a WDM WAN consists of clear channels between nodes called lightpaths, with traffic carried from source to destination without electronic switching "as far as possible", but some electronic switching may be performed. Virtual topology design aims at combining the best of optical switching and electronic routing abilities. Designing a virtual topology on a physical network consists of deciding the lightpaths to be set up in terms of their source and destination nodes and wavelength assignment. In this survey we first describe the context and motivations of the virtual topology design ...
Design of logical topologies: A linear formulation for wavelengthrouted optical networks with no wavelength changers
 IEEE/ACM Transactions on Networking
, 2001
"... Abstract—We consider the problem of constructing logical topologies over a wavelengthrouted optical network with no wavelength changers. We present a general linear formulation which considers routing traffic demands, and routing and assigning wavelengths to lightpaths, as a combined optimization ..."
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Cited by 71 (0 self)
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Abstract—We consider the problem of constructing logical topologies over a wavelengthrouted optical network with no wavelength changers. We present a general linear formulation which considers routing traffic demands, and routing and assigning wavelengths to lightpaths, as a combined optimization problem. The formulation also takes into account the maximum number of hops a lightpath is permitted to take, multiple logical links in the logical topology, multiple physical links in the physical topology, and symmetry/asymmetry restrictions in designing logical topologies. The objective is to minimize congestion. We show by examples how equality and inequality logical degree constraints have a bearing on congestion. We prove that, under certain conditions, having equality degree constraints with multiple edges allowed in the design of logical topologies does not affect congestion. This helps in reducing the dimensionality of the search space and hence speeds up the search for an optimal solution of the linear formulation. We solve the linear formulation for small examples and show the tradeoff between congestion, number of wavelengths available and the maximum number of hops a lightpath is allowed to take. For large networks, we solve the linear formulation by relaxing the integer constraints. We develop topology design algorithms for large networks based on rounding the solutions obtained by solving the relaxed problem. Since the whole problem is linearizable, the solution obtained by relaxation of the integer constraints yields a lower bound on congestion. This is useful in comparing the efficiency of our heuristic algorithms. Following Bienstock and Gunluk, 1995, we introduce a cutting plane which helps in obtaining better lower bounds on congestion and also enables us to reduce the previously obtained upper bounds on congestion. Index Terms—Alloptical networks, linear program, network planning, topology design.
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 59 (1 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.
Experience in measuring backbone traffic variability: Models, metrics, measurements and meaning
 in ACM SIGCOMM Internet Measurement Workshop
, 2002
"... Abstract—Understanding the variability of Internet traffic in backbone networks is essential to better plan and manage existing networks, as well as to design next generation networks. However, most traffic analyses that might be used to approach this problem are based on detailed packet or flow lev ..."
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Cited by 31 (6 self)
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Abstract—Understanding the variability of Internet traffic in backbone networks is essential to better plan and manage existing networks, as well as to design next generation networks. However, most traffic analyses that might be used to approach this problem are based on detailed packet or flow level measurements, which are usually not available throughout a large network. As a result there is a poor understanding of backbone traffic variability, and its impact on network operations (e.g. on capacity planning or traffic engineering). This paper introduces a metric for measuring backbone traffic variability that is grounded on simple but powerful traffic theory. What sets this metric apart, however, is that we present a method for making practical measurements of the metric using widely available SNMP traffic measurements. Furthermore, we use a novel method to overcome the major limitation of SNMP measurements – that they only provide link statistics. The method, based on a “gravity model”, derives an approximate traffic matrix
Offline configuration of a MPLS over WDM network under timevarying offered traffic
 IN TWENTYFIRST ANNUAL JOINT CONFERENCE OF THE IEEE COMPUTER AND COMMUNICATIONS SOCIETIES (IEEE
, 2002
"... ... wavelengthrouted WDM layer offersgreat flexibility to operatorsto allocate traffic demandsin their networks. In this paper we consider the problem of offline joint configuration at both packet and optical layers. We consider timevariant offered traffic, and assume that the operator has knowle ..."
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Cited by 28 (3 self)
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... wavelengthrouted WDM layer offersgreat flexibility to operatorsto allocate traffic demandsin their networks. In this paper we consider the problem of offline joint configuration at both packet and optical layers. We consider timevariant offered traffic, and assume that the operator has knowledge of the traffic dynamicsasa set of traffic matricesat different instants. A novel Mixed Integer Linear Programming (MILP) formulation isproposed, which takesin input this set of traffic matrices, and provide an optimal static configuration capable of accomodating the timevarying traffic. We provide a resolution strategy based on heuristics, and give numerical results for some sample cases. The proposed method iscompared with a simple alternative approach for obtaining a single static solution, to show that our method utilizes much less resources. The solution under the proposed formulation is also compared with the set of solutions obtained by running distinct optimization problems at different instants, showing that the increase of resource is minimal. Hence our approach can provide a static configuration with about the same resources of a fully adaptable dynamical configuration.
Efficient Routing and Wavelength Assignment for Reconfigurable WDM Networks with Wavelength Converters
, 2003
"... We consider the problem of wavelength assignment in a reconfigurable bidirectional ring network with wavelength converters. We show that for Nnode P port bidirectional rings, a minimum number of wavelengths are required to support all possible virtual topologies in a rearrangeably nonblocking ..."
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Cited by 28 (3 self)
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We consider the problem of wavelength assignment in a reconfigurable bidirectional ring network with wavelength converters. We show that for Nnode P port bidirectional rings, a minimum number of wavelengths are required to support all possible virtual topologies in a rearrangeably nonblocking fashion, and provide an algorithm that meets this bound for connected topologies using no more than wavelength converters. This improves over the tight lower bound of required for such rings given in [1] if no wavelength conversion is available. We also provide another algorithm that uses more wavelengths yet requires significantly fewer converters. Both algorithms are then extended to the case of unconnected topologies using at most one additional wavelength. Finally, we develop a method that allows the wavelength converters to be arbitrarily located at any node in the ring. This gives significant flexibility in the design of the networks. For example, all can be collocated at a single hub node, or distributed evenly among the N nodes with converters at each node.
Experience in Measuring Internet Backbone Traffic Variability: Models, Metrics, Measurements and Meaning
 in Proceedings of the International Teletraffic Congress (ITC18
, 2003
"... This paper introduces a metric for measuring backbone traffic variability that is grounded on simple but powerful traffic theory. What sets this metric apart, however, is that we present a method for practical implementation of the metric using widely available SNMP traffic measurements. In addition ..."
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Cited by 26 (10 self)
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This paper introduces a metric for measuring backbone traffic variability that is grounded on simple but powerful traffic theory. What sets this metric apart, however, is that we present a method for practical implementation of the metric using widely available SNMP traffic measurements. In addition to simulations, we use a large set of SNMP data from an operational IP network on the order of 1000 nodes to test our methods. We also delve into the degree and sources of variability in real backbone traffic, providing insight into the true nature of traffic variability
Characterization of graphs and digraphs with small process number
, 2009
"... We introduce the process number of a digraph as a tool to study rerouting issues in wdm networks. This parameter is closely related to the vertex separation (or pathwidth). We consider the recognition and the characterization of (di)graphs with small process number. In particular, we give a linear t ..."
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Cited by 21 (16 self)
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We introduce the process number of a digraph as a tool to study rerouting issues in wdm networks. This parameter is closely related to the vertex separation (or pathwidth). We consider the recognition and the characterization of (di)graphs with small process number. In particular, we give a linear time algorithm to recognize (and process) graphs with process number at most 2, along with a characterization in terms of forbidden minors, and a structural description. As for digraphs with process number 2, we exhibit a characterization that allows to recognize (and process) them in polynomial time.
WDM Network Optimization by ILP Based on Source Formulation
 IN PROCEEDINGS OF IEEE INFOCOM
, 2002
"... Efficient planning and optimization of wavelength division multiplexing networks is an important issue today. Integer Linear Programming (ILP) is the most used exact method to perform this task. In this paper we propose a new ILP formulation that allows to solve optimization with less computational ..."
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Cited by 17 (0 self)
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Efficient planning and optimization of wavelength division multiplexing networks is an important issue today. Integer Linear Programming (ILP) is the most used exact method to perform this task. In this paper we propose a new ILP formulation that allows to solve optimization with less computational effort compared to other ILP approaches. This formulation applies to multifiber mesh networks with or without wavelength conversion, when either the total fiber number or the total fiber length is the cost function to be minimized. After presenting the formulation we discuss the results we obtained by exploiting it in the optimization of two casestudy networks.