Davide Cherubini - PhD Thesis - UniCA Eprints

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7.2 The highly meshed networkA unit link metrics value has been assigned to all arcs (default configurationsuggested by the major router vendors). Note that in that case, the shortestpaths are those with the minimum number of hops.The obtained results have been also compared with those of the IS-IS metricsoptimization performed using a metaheuristics algorithm (in particular a TabuSearch algorithm implemented by the research group of University of Cagliari[60]), which considers the failure scenarios in the search process.The LP model have been applied starting from the conditions above describedand, as shown in Table 7.2, the objective function value has been evaluatedand compared in both “normal condition” (solution of the GRP) and in “failurecondition” (adding the survivability constraint).The last column of Table 7.2 shows the number of explicit LSPs determined bythe model.Phase Normal Condition Failure Condition # LSPIS-IS Default Routing u max = 34% u max = 70% 0IS-IS optimization u max = 29% u max = 47% 0MPLS optimization u max = 23% u max = 35% 55Joint IS-IS/MPLS opt. u max = 23% u max = 35% 48Table 7.2: Comparing results for the synthetic networkResults discussionThe obtained results show that the application of the model starting either fromthe “default” configuration or the “IS-IS optimal configuration”, produces thesame maximum link utilization. Only the number of LSPs needed changes andthis may depend on the fact that (likely) the IS-IS optimization already identifiessome best paths.It is important to note that, in case of failure, the maximum link occupation hasbeen halved with respect to the “default” configuration.67
7.3 The IBCN European network7.3 The IBCN European networkThe second benchmark network is part of the Zuse Institute Berlin’s (ZIB) SNDlib[22], that is a library of test instances for Survivable fixed telecommunicationNetwork Design.The problem was originally defined as a capacity planning problem and hasbeen provided by the INTEC Broadband Communication Networks researchgroup (IBCN) which is a research institute founded by the Flemish Government,focusing on information & communication technology (ICT) in general, and applicationsof broadband technology in particular [12].During the tests, the links capacity has been fixed and the demands valueshave been scaled in order to obtain a slight congestion in case of failure when the“default” configuration is used.The topology contains n = 37 nodes widely spread in the European territoryand m = 114 directed arcs, The characteristics described are summarized in Table7.3, while the network topology is shown in Figure 7.2.The traffic matrix is given as part of the instance with n·(n−1) = 1332 commodities(flows), thus the resulting problem has 5551 variables and 5813 constraints.Nodes 37Arcs 114Flows 1332Variables 5551Constraints 5813Table 7.3: Characteristics of the IBCN European networkRouting OptimizationAs preliminary step, the optimal solution of the GRP has been found using theLP model, with all constraints but the survivability one, and results have beencompared with those obtained by the “default” configuration as well as by theIS-IS metrics optimization process.68
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AcknowledgementsThis dissertation w
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AbstractThis dissertation investiga
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CONTENTS7.4 The Real ISP’s Italia
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LIST OF FIGURES7.3 Default metrics
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1.2 Objectives of the dissertation2
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Chapter 2Basic knowledgeThis chapte
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2.1 Understanding IS-IS• A = sour
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2.2 Understanding MPLS Technology2.
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2.2 Understanding MPLS TechnologyTh
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2.4 Restoration SchemesHowever, fai
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3.1 Optimization of IS-IS/OSPF rout
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Page 65 and 66: 6.4 LP modelsEquation 6.32 is the o
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Page 73 and 74: 6.4 LP models∑f∈Fx f,lij⎛⎝i
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Page 97 and 98: REFERENCES[14] Jones Lustig Format
Page 99 and 100: REFERENCES[40] A. V. Fiacco and G.
Page 101: REFERENCES[61] A. Nucci, B. Schroed
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Davide Cherubini - PhD Thesis - UniCA Eprints

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