1. Factors Affecting the Efficiency of Demand-wise Shared Protection Brian Forst, Wayne D. Grover Contact: bforst@trlabs.ca, grover@trlabs.ca 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

2. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 2 Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

3. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 3 Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

4. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 4 1+1 Automatic Protection Switching (APS) Oldest and simplest protection architecture Minimum 100% redundancy Fastest protection A B X Working path

5. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 5 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

6. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 6 DSP A B Working paths

7. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 7 DSP A B X

8. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 8 DSP A B X

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

10. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 10 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

11. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 11 Network Topologies Two families of networks: Degree 3 Degree 4 AmericaEuropeGermany 15 Node20 Node25 Node

12. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 12 Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

13. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 13 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

14. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 14 Overview Background –1+1 APS –DSP Methodology & Network Families Design Results Practical Methods to Increase Efficiency Conclusion

15. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 15 What to do? Small savings over 1+1 APS found –Nowhere near SBPP values. Six areas of concern have been identified

16. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 16 1: Average Network Nodal Degree Degree 4 networks have higher savings than degree 3 –Greater amounts of disjoint routes

17. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 17 2: Demand Splitting Restrictions (Magnitude) Integer amounts of demand –Cannot be further sub-divided BA d AB = 2 BA d AB = 1

18. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 18 3: 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

19. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 19 4: Diminishing Returns of Greater Splitting 50% reduction in spare capacity 17% further reduction in spare capacity

20. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 20 5: 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

21. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 21 5: Degree 2 Nodes and Chains EuropeGermany

22. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 22 6: Rapid Cost Increase of Higher Order Routes Remember this equation? We are fighting against it Two important ratios

23. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 23 6: 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 = 1.55100%R 2 /R 1 = 1.95

24. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 24 6: 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 = 1.55100%R 2 /R 1 = 1.95 100%R 3 /R 1 = 2.31 50%R 3 /R 1 = 3.55 40%R 4 /R 1 = 3.23 1%R 4 /R 1 = 3.55 6%R 5 /R 1 = 4.85 0%R 5 /R 1 = N/A <1%R 6 /R 1 = 9.10 0%R 6 /R 1 = N/A

25. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 25 6: 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

26. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 26 6: Rapid Cost Increase of Higher Order Routes Second ratio: R n /(R 1 + R 2 ) Degree 3Degree 4

27. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 27 6: Rapid Cost Increase of Higher Order Routes 6 disjoint routes B A 25 Node

28. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 28 6: 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

29. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 29 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

30. October 9, 2007 Factors Affecting the Efficiency of Demand-wise Shared Protection DRCN 2007 30 Questions?