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12
A genetic algorithm for the weight setting problem in OSPF routing
 Journal of Combinatorial Optimization
, 2002
"... Abstract. With the growth of the Internet, Internet Service Providers (ISPs) try to meet the increasing traffic demand with new technology and improved utilization of existing resources. Routing of data packets can affect network utilization. Packets are sent along network paths from source to desti ..."
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Cited by 77 (22 self)
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Abstract. With the growth of the Internet, Internet Service Providers (ISPs) try to meet the increasing traffic demand with new technology and improved utilization of existing resources. Routing of data packets can affect network utilization. Packets are sent along network paths from source to destination following a protocol. Open Shortest Path First (OSPF) is the most commonly used intradomain Internet routing protocol (IRP). Traffic flow is routed along shortest paths, splitting flow at nodes with several outgoing links on a shortest path to the destination IP address. Link weights are assigned by the network operator. A path length is the sum of the weights of the links in the path. The OSPF weight setting (OSPFWS) problem seeks a set of weights that optimizes network performance. We study the problem of optimizing OSPF weights, given a set of projected demands, with the objective of minimizing network congestion. The weight assignment problem is NPhard. We present a genetic algorithm (GA) to solve the OSPFWS problem. We compare our results with the best known and commonly used heuristics for OSPF weight setting, as well as with a lower bound of the optimal multicommodity flow routing, which is a linear programming relaxation of the OSPFWS problem. Computational experiments are made on the AT&T Worldnet backbone with projected demands, and on twelve instances of synthetic networks. 1.
Experimental analysis of dynamic all pairs shortest path algorithms
 In Proceedings of the fifteenth annual ACMSIAM symposium on Discrete algorithms
, 2004
"... We present the results of an extensive computational study on dynamic algorithms for all pairs shortest path problems. We describe our implementations of the recent dynamic algorithms of King and of Demetrescu and Italiano, and compare them to the dynamic algorithm of Ramalingam and Reps and to stat ..."
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Cited by 36 (5 self)
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We present the results of an extensive computational study on dynamic algorithms for all pairs shortest path problems. We describe our implementations of the recent dynamic algorithms of King and of Demetrescu and Italiano, and compare them to the dynamic algorithm of Ramalingam and Reps and to static algorithms on random, realworld and hard instances. Our experimental data suggest that some of the dynamic algorithms and their algorithmic techniques can be really of practical value in many situations. 1
Survivable IP network design with OSPF routing
 Networks
, 2006
"... Abstract. Internet protocol (IP) traffic follows rules established by routing protocols. Shortest path based protocols, such as Open Shortest Path First (OSPF), direct traffic based on arc weights assigned by the network operator. Each router computes shortest paths and creates destination tables us ..."
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Cited by 9 (7 self)
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Abstract. Internet protocol (IP) traffic follows rules established by routing protocols. Shortest path based protocols, such as Open Shortest Path First (OSPF), direct traffic based on arc weights assigned by the network operator. Each router computes shortest paths and creates destination tables used for routing flow on the shortest paths. If a router has multiple outgoing links on shortest paths to a given destination, it splits traffic evenly over these links. It is also the role of the routing protocol to specify how the network should react to changes in the network topology, such as arc or router failures. In such situations, IP traffic is rerouted through the shortest paths not traversing the affected part of the network. This paper addresses the issue of assigning OSPF weights and multiplicities to each arc, aiming to design efficient OSPFrouted networks with minimum total weighted multiplicity (multiplicity multiplied by the arc length) needed to route the required demand and handle any single arc or router failure. The multiplicities are limited to a discrete set of values and we assume that the topology is given. We propose an evolutionary algorithm for this problem, and present results applying it to several realworld problem instances. 1.
Shortest Path Trees Computation in Dynamic Graphs
, 2005
"... Let G =(V,E,w) be a simple digraph, in which all edge weights are nonnegative real numbers. Let G ′ be obtained from G by the application of a set of edge weight updates to G. Lets∈V, and let Ts and T ′ s be a Shortest Path Tree (SPT) rooted at s in G and G ′ , respectively. The Dynamic Shortest Pa ..."
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Cited by 3 (0 self)
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Let G =(V,E,w) be a simple digraph, in which all edge weights are nonnegative real numbers. Let G ′ be obtained from G by the application of a set of edge weight updates to G. Lets∈V, and let Ts and T ′ s be a Shortest Path Tree (SPT) rooted at s in G and G ′ , respectively. The Dynamic Shortest Path (DSP) problem is to compute T ′ s from Ts. For the DSP problem, we correct and extend a few existing SPT algorithms to handle multiple edge weight updates. We prove that these extended algorithms are correct. The complexity of these algorithms is also analyzed. To evaluate the proposed algorithms, we compare them with the wellknown static Dijkstra algorithm. Extensive experiments are conducted with both reallife and artificial data sets. The reallife data are road system graphs obtained from the Connecticut road system and are relatively sparse. The artificial data are randomly generated graphs and are relatively dense. The experimental results suggest the most appropriate algorithms to be used under different circumstances.
Fast paths in largescale dynamic road networks
, 2007
"... Efficiently computing fast paths in largescale dynamic road networks (where dynamic traffic information is known over a part of the network) is a practical problem faced by several traffic information service providers who wish to offer a realistic fast path computation to GPS terminal enabled vehi ..."
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Cited by 3 (0 self)
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Efficiently computing fast paths in largescale dynamic road networks (where dynamic traffic information is known over a part of the network) is a practical problem faced by several traffic information service providers who wish to offer a realistic fast path computation to GPS terminal enabled vehicles. The heuristic solution method we propose is based on a highway hierarchybased shortest path algorithm for static largescale networks; we maintain a static highway hierarchy and perform each query on the dynamically evaluated network, using a simple algorithm to propagate available dynamic traffic information over a larger part of the road network. We provide computational results that show the efficacy of our approach. 1
AN OPTIMIZER IN THE TELECOMMUNICATIONS INDUSTRY
"... Abstract. This article relates some combinatorial optimization problems encountered by an optimizer in an industrial research laboratory at AT&T, a large telecommunications company. The article will appear in the Fall 2007 issue of SIAM SIAG/Optimization ViewsandNews which will try to cover some a ..."
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Cited by 2 (2 self)
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Abstract. This article relates some combinatorial optimization problems encountered by an optimizer in an industrial research laboratory at AT&T, a large telecommunications company. The article will appear in the Fall 2007 issue of SIAM SIAG/Optimization ViewsandNews which will try to cover some aspects of the industrial applications of optimization and of the life of optimizers at AT&T, IBM, and Exxon. 1.
Shortest paths on dynamic graphs
, 2008
"... Among the variants of the well known shortest path problem, those that refer to a dynamically changing graphs are theoretically interesting, as well as computationally challenging. Applicationwise, there is an industrial need for computing pointtopoint shortest paths on largescale road networks w ..."
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Cited by 2 (2 self)
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Among the variants of the well known shortest path problem, those that refer to a dynamically changing graphs are theoretically interesting, as well as computationally challenging. Applicationwise, there is an industrial need for computing pointtopoint shortest paths on largescale road networks whose arcs are weighted with a travelling time which depends on traffic conditions. We survey recent techniques for dynamic graph weights as well as dynamic graph topology. 1
Bidirectional A ∗ Search on TimeDependent Road Networks
, 2010
"... The computation of pointtopoint shortest paths on timedependent road networks has a large practical interest, but very few works propose efficient algorithms for this problem. We propose a novel approach which tackles one of the main complications of route planning in timedependent graphs, which ..."
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Cited by 2 (1 self)
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The computation of pointtopoint shortest paths on timedependent road networks has a large practical interest, but very few works propose efficient algorithms for this problem. We propose a novel approach which tackles one of the main complications of route planning in timedependent graphs, which is the difficulty of using bidirectional search: since the exact arrival time at the destination is unknown, we start a backward search from the destination node using lower bounds on arc costs in order to restrict the set of nodes that have to be explored by the forward search. Our algorithm is based on A ∗ with landmarks (ALT); extensive computational results show that it is very effective in practice if we are willing to accept a small approximation factor, resulting in a speedup of more than one order of magnitude with respect to Dijkstra’s algorithm while finding only slightly suboptimal solutions. The main idea presented here can also be generalized to other types of search algorithms.
Batch Dynamic SingleSource ShortestPath Algorithms: An Experimental Study
, 2009
"... A dynamic shortestpath algorithm is called a batch algorithm if it is able to handle graph changes that consist of multiple edge updates at a time. In this paper we focus on fullydynamic batch algorithms for singlesource shortest paths in directed graphs with positive edge weights. We give an exte ..."
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Cited by 1 (0 self)
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A dynamic shortestpath algorithm is called a batch algorithm if it is able to handle graph changes that consist of multiple edge updates at a time. In this paper we focus on fullydynamic batch algorithms for singlesource shortest paths in directed graphs with positive edge weights. We give an extensive experimental study of the existing algorithms for the singleedge and the batch case, including a broad set of test instances. We further present tuned variants of the already existing SWSFFPalgorithm being up to 15 times faster than SWSFFP. A surprising outcome of the paper is the astonishing level of data dependency of the algorithms.
Heuristic Improvements in Multicommodity Flow Algorithm
"... Abstract. We propose heuristic improvements in the procedure to obtain a (1+ω)approximation of the multicommodity flow which satisfies all demands when the cost bound is given as an input parameter. Through a series of improvements we are able to significantly reduce the number of shortest path com ..."
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Abstract. We propose heuristic improvements in the procedure to obtain a (1+ω)approximation of the multicommodity flow which satisfies all demands when the cost bound is given as an input parameter. Through a series of improvements we are able to significantly reduce the number of shortest path computations. We also present a new version of the algorithm given in [1] which is amenable to our optimizations. Finally we compare our results against those given in [2] and demonstrate significant improvement in the results. We also propose methods to reduce the running time of the algorithm. 1