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,

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… ?

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

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

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

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

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

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 Expected Future Cost Total Cost Difference0.10%23.65%42.01%60.56%

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

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

OFC 2004, Los Angeles, CA Thank You.

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 = Sharing of spare capacities