Factors Affecting the Efficiency of Demand-wise Shared Protection Brian Forst, Wayne D. Grover Contact: Electrical and Computer Engineering University of Alberta 2nd Floor, 9107 – 116 Street Edmonton, Alberta, Canada T6G 2V4 Network Systems Group TRLabs 7th Floor, 9107 – 116 Street Edmonton, Alberta, Canada T6G 2V4

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Automatic Protection Switching (APS) Oldest and simplest protection architecture Minimum 100% redundancy Fastest protection A B X Working path

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Why Demand-wise Shared Protection (DSP)? Renewed interest in 1:N DP APS as a network protection architecture Promising aspects include: –Fast failure-response times –Full pre-failure cross-connection of backup paths –No fault localization required –Conceptually simple to understand –Technically possible to operate in current networks –Possibility of low redundancy/high efficiency protection Motivation for this study: –In recent studies DSP is not exhibiting the low redundancy we expected it could achieve

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN DSP A B Working paths

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN DSP A B X

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN DSP A B X

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Methodology Obtain DSP and APS design results –Hop-based costs –Distance-based costs Analyze route-cost statistics New ILP model and method to calculate route-cost statistics

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Network Topologies Two families of networks: Degree 3 Degree 4 AmericaEuropeGermany 15 Node20 Node25 Node

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Design Results Hop-based costs –Degree 3 Networks: 1%, 1% and 7% savings relative to APS –Degree 4 Networks: 11% - 12% savings relative to APS Distance-based costs –Degree 3 Networks: 0.3%, 2.5% and 5.5% savings relative to APS –Degree 4 Networks: 8% - 9% savings relative to APS Here, hop-based costing gives greater reductions

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN What to do? Small savings over 1+1 APS found –Nowhere near SBPP values. Six areas of concern have been identified

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Average Network Nodal Degree Degree 4 networks have higher savings than degree 3 –Greater amounts of disjoint routes

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Demand Splitting Restrictions (Magnitude) Integer amounts of demand –Cannot be further sub-divided BA d AB = 2 BA d AB = 1

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Demand Splitting Restrictions (Divisibility) APSDSP d AB = 3 BA w 1 = 3 s = 3 Cost = 6 BA w 1 = 2 s = 2 w 2 = 1 Cost = 5 d AB = 4 BA w 1 = 4 s = 4 Cost = 8 BA w 1 = 2 s = 2 w 2 = 2 Cost = 6

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Diminishing Returns of Greater Splitting 50% reduction in spare capacity 17% further reduction in spare capacity

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Degree 2 Nodes and Chains Europe: 32% (9 of 28) Germany: 41% (7 of 17) America: 15% (2 of 14) A 1.5% Savings6% Savings Germany

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Degree 2 Nodes and Chains EuropeGermany

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes Remember this equation? We are fighting against it Two important ratios

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes First ratio: R n /R 1 Approximately 600 O-D pairs in each family Degree 3 FamiliesDegree 4 Families 100%R 2 /R 1 = %R 2 /R 1 = 1.95

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes First ratio: R n /R 1 Approximately 600 O-D pairs in each family Degree 3 FamiliesDegree 4 Families 100%R 2 /R 1 = %R 2 /R 1 = %R 3 /R 1 = %R 3 /R 1 = %R 4 /R 1 = %R 4 /R 1 = %R 5 /R 1 = %R 5 /R 1 = N/A <1%R 6 /R 1 = %R 6 /R 1 = N/A

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes Second ratio: R n /(R 1 + R 2 ) R 3 Case: R 1 : 2 workR 2 : 2 spare Cost = 2R 1 + 2R 2 R 3 = 1 work R 1 = 1 workR 2 = 1 spare If R 3 = R 1 + R 2 = R 1 + R 2 + (R 1 + R 2 ) = 2R 1 + 2R 2 Cost AB d AB = 2

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes Second ratio: R n /(R 1 + R 2 ) Degree 3Degree 4

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes 6 disjoint routes B A 25 Node

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN : Rapid Cost Increase of Higher Order Routes Only 2 used in optimal solution! A B 25 Node First two routes: 400 km Third route: 410 km R 3 /(R 1 +R 2 ) > 1

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Conclusion New ILP model Identified important factors –Higher order route costs –Degree 2 nodes –Unit capacity (single-channel) demands Guideline for the application of DSP –3-way splits These are new insights that give us an understanding of what limits the attainable efficiency of DSP

October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN Questions?