Davide Cherubini - PhD Thesis - UniCA Eprints

7.4 The Real ISP’s Italian Backbone NetworkNodes 18Arcs 54Flows 306Variables 1279Constraints 1402Table 7.6: Characteristics of the Tinet Italian backboneRouting OptimizationThe objective function value comparison shown in Table 7.7 highlights the congestionlevel reduction granted by the optimization processes.In particular, the MPLS optimization allows dropping the maximum utilizationby 10.6%, with respect to the ISP’s IS-IS configuration, using only 105 LSPs.Histograms report the occupation of the links in three different scenarios:• ISP’s IS-IS metrics (Figure 7.10)• IS-IS optimized metrics (with Tabu Search) (Figure 7.11)• MPLS optimization (Figure 7.12)Phase u max % Gain (Def) % Gain (Tis) # LSPDefault u max = 72% – – 0Tiscali u max = 66% 8.3% – 0IS-IS opt. u max = 61% 15.2% 7.6% 0MPLS opt. u max = 59% 18.1% 10.6% 105Table 7.7: Routing optimization for the Tinet network76