1. OFC 2004, Los Angeles, CA Restorable Mesh Network Design under Demand Uncertainty: Toward “Future Proofed” Transport Investments Dion Leung, Wayne Grover Network Systems, TRLabs University of Alberta, Edmonton {dion.leung, grover}@trlabs.ca

2. OFC 2004, Los Angeles, CA Actual Demand Increasing Uncertainty in Demand Forecast Physical Topology Optimize… Deregulation? New data applications? Economic variability? Customer churn? Demand Forecast Network Survivability: span restoration path protection Minimum Cost Design The min-cost design is no longer optimal… ?

3. OFC 2004, Los Angeles, CA Analyzing Uncertainty Using Post-Verification Techniques Minimum Cost Design Analyze… What-if Scenario 1 What-if Scenario 2 What-if Scenario 3 Sensitivity Report: Scenario 1 Scenario 2 Scenario 3

4. OFC 2004, Los Angeles, CA Re-define Capacity Planning as Two-stage Decision Problem Conventional Design singleUse a single best-guess forecast for capacity planning A single-period planning problem Snapshot design optimal to a single moment in time “Future-Proof” Design multipleUse multiple demand scenarios (e.g. the what-if scenarios) to model demand uncertainty recourseConsider “corrective” or recourse action to cope with actual outcome present futureOptimize both the present investment and the expected future outcomes Present InvestmentFuture Investment + Recourse

5. OFC 2004, Los Angeles, CA Conventional Span-Restorable Capacity Design Minimize Network Cost Routability Constraint >> All demands must be routed Survivability Constraint >> All demands must be restorable

6. OFC 2004, Los Angeles, CA Expected Future Cost “Future-Proof” “Future-Proof” Survivable Network Design Minimize Initial Design Cost Routability Constraint >> All demands must be routed Survivability Constraint >> All demands must be restorable Allow Recourse: Add Extra Capacity if Needed

7. OFC 2004, Los Angeles, CA 11 nodes, 26 spans A Case Study on COST239 Network k = 1 k = 20 P(k=1) P(k=20) 20 Demand Scenarios Represent Alternate Futures Prob(k) For Span A Present Cost, C span A Future Cost, R span A = C span A *X For Span B Present Cost, C span B Recourse Cost, R span B *X

8. OFC 2004, Los Angeles, CA Comparing Conventional and Future-Proof Designs Conv.FP-SRConv.FP-SRConv.FP-SRConv.FP-SR Recourse Cost Factor 1 * C j 2 * C j 3 * C j 5 * C j Initial Cost 202185203340202185644085202185703815202185789300 Expected Future Cost 4074804057138146781322571221759121951203710693781 Total Cost 609665609053101686377634214239448257662239291883081 Difference0.10%23.65%42.01%60.56%

9. OFC 2004, Los Angeles, CA Highest Recourse Tradeoff between Present and Long Term Costs Low Recourse

10. OFC 2004, Los Angeles, CA Summary and Future Work demand uncertaintyPropose a new approach to design mesh restorable networks under demand uncertainty (the model can also be easily adapted to other survivability schemes, such as p-cycles and path protection) recourse two-stageDefine the notion of recourse and show the advantages of considering the design as a two-stage decision problem (possible to extend this problem to a multi-stage problem) future network planning toolsSuggest a new design strategy of planning against uncertainty for future network planning tools Present InvestmentFuture Investment + Recourse

11. OFC 2004, Los Angeles, CA Thank You. dion.leung@trlabs.ca

12. OFC 2004, Los Angeles, CA Illustration of Span (or Link) Restoration Scheme Localized restoration between the end nodes of the failed span Multiple restoration paths are used for a span failure span X, w 1 = 3 span Y, w 2 = 5 1 2 1 2 3 2 Sharing of spare capacities