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The Changing Mix of Protection and Restoration Mechanisms in Core Optical Mesh Networks

The Changing Mix of Protection and Restoration Mechanisms in Core Optical Mesh Networks. Jonathan Weston-Dawkes Principal Network Architect Corvis Corporation. Or…Why Optical Networks are good for mesh restoration!. Thanks to Sachin Kulkarni for algorithm implementation.

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The Changing Mix of Protection and Restoration Mechanisms in Core Optical Mesh Networks

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  1. The Changing Mix of Protection and Restoration Mechanisms in Core Optical Mesh Networks Jonathan Weston-Dawkes Principal Network Architect Corvis Corporation

  2. Or…Why Optical Networks are good for mesh restoration! Thanks to Sachin Kulkarni for algorithm implementation

  3. What you should remember… • All-Optical Networks (with ULH and optical bypass) are known to make 1+1 protection architectures attractive • Traditional mesh restoration assumes spare bandwidth is allocated on short optical connections between adjacent OXC to maximize bandwidth efficiency • Results of this study show that optical bypass provides significant cost savings for the spare bandwidth in mesh restoration architectures with little loss in efficiency • Better yet, combining 1+1 with mesh restoration reduces cost even more • Carriers thus have great flexibility in how they provide service availability and bandwidth efficiency • ULH plays an important role in all of this

  4. Outline • Short History • Grooming Architecture • Objectives of Restoration Study • Methodology • Impact of optical reach on restoration design • Summary

  5. Recent History of Carrier Restoration Issues • Early-Mid ’90s • Emergence of SONET/SDH shared protection rings • DS3 mesh vs. rings • Efficiency of ring designs • Nodal cost of DS3 cross connect • Pre-amplifier networks dominated by regen cost • Mid-Late ’90s • SONET/SDH rings • Mesh equipment protection in early WDM networks • Exploration of optical ring and optical mesh solutions • 2000+ • Introduction of ULH, optical bypass, Tbps capacity WDM systems • Comparison of 1+1 with OC-192 shared mesh restoration

  6. x x x x x x x Layered Service Network / DWDM Transport Infrastructure • Concurrent support of LH, ELH and ULHtransmission, with OADMs and Transparent Optical Switches • We assume this optical network infrastructure is in place, and focus on the incremental equipment (transponders, OXC ports) needed to add traffic Service Grooming & Protection ULH LH ELH DWDM Transport Infrastructure with Optical Bypass Unified Network Platform Transparent Optical Switch Transparent OADM Grooming Edge OXC x

  7. First Intermediate Grooming OXC Last Intermediate Grooming OXC Intermediate Grooming Hubs Grooming OXC Grooming OXC OC-192 from OXC to Hub OC-192 from OXC to Hub Direct OC-192 Between OXC Route Choice Optical bypass with Optical Switch or OADM 1st 2nd Groom Groom 3rd Groom Groom Groom First-and-Last Grooming Architecture

  8. Intermediate Grooming Sites With first-and-last grooming, ULH has significant role for working paths as well as dedicated protection paths

  9. Objectives of Current Study • Determine how to use optical reach optimally in the design of core carrier networks • Sensitivity of design to optical reach value for mesh restoration • Comparison of 1+1 dedicated protection with shared mesh restoration • Identifying the value of mixing 1+1 with shared mesh • % of 1+1 as a function of optical reach

  10. OXC 10G port LH Tx/Rx LH Regen 1.00 1.00 1.33 ELH Tx/Rx ELH Regen 1.66 2.33 ULH Tx/Rx ULH Regen 2.00 3.00 Mesh Restoration Assumptions • Demands created by first-and-last grooming • 100% survivability for all single fiber span cuts • May affect more than one OXC link • Failure-independent path mesh of OC-192 demands • Single working path (with 1 or more OC-192 demands) may have multiple restoration paths • No reuse of working path bandwidth during restoration • Restoration switching provided by edge OXC • Optical Network provides bypass, not switching • Fixed cost assumptions (independent of reach) • OXC 10G port: 1 • WDM Tx/Rx transponder: 2 • Regenerator: 3 • Mixed cost assumptions (reach dependent)

  11. Heuristic Mesh Restoration Algorithm • Iterative greedy heuristic algorithm for generating a near optimal spare bandwidth allocation and restoration path assignment • Each iteration considers several demand orderings • For a given ordering, each demand is assigned • a working path based on least cost (or least cost with load balancing factor) • a protection path, avoiding the SRLGs and tandem nodes in working path, based on shortest path with metric derived from current spare bandwidth allocation • The result of an iteration is a set of spare bandwidth assumed for next iteration, together with a set of existing demand orderings kept and a number of new orderings generated for next iteration

  12. Comparison of Mesh Design Heuristic with Other Techniques Ref: Y. Liu, Ph’d Dissertation, University of Pittsburgh Heuristic Mesh Restoration Algorithm

  13. Design Methodology • Construct a chain of OXC topologies wrt inclusion, subject to constraint that demand working path SRLGs remain the same • G0 G1 G2 … s.t. srlg(Dw,Gi) = srlg(Dw,Gj) • G0 = Topology A = fiber topology • G1 = Topology B = A + short express links • G2 = Topology C = B + longer express links • For each topology, determine mesh restoration design using heuristic algorithm, then • 100% Mesh Scenario: Apply post-optimization procedure 1 to reduce network cost by swapping existing restoration path with new one • Hybrid Scenario: Apply post-optimization procedure 2 to reduce network cost either by swapping to new restoration path in mesh or moving demand to dedicated protection • Compare with 100% dedicated protection design

  14. OXC Topologies A, B, and C in Chain Topology A uses the links in the fiber topology Add express links to Topology A to build Topology B Add more express links to Topology B to build Topology C

  15. Traditional Mesh Restoration ULH appears to have almost no role in mesh restoration links Mixed Costs were assumed

  16. Topology B Mesh Restoration ULH has role in mesh restoration if Topology B or C design is economical Mixed Costs were assumed

  17. Results of Optimized Designs

  18. Mesh Restoration Bandwidth Cost 180 160 140 Dedicated 120 100 Topology A 80 Topology B 60 Relative Cost Topology C 40 20 Reference Cost of 100 assigned to mesh restoration design with no bypass (Topology A) with 500km optical reach 0 500 1000 1500 2000 2500 3000 Optical Reach At 1500km optical reach, mesh restoration with no bypass and 100% dedicated protection have same cost At 3000km optical reach, mesh restoration with bypass and 100% dedicated protection have similar cost 100% Mesh Restoration Link Cost Comparison Fixed Costs were assumed

  19. At 1500km optical reach, hybrid mesh restoration on Topology A with 22% dedicated protection is now much less expensive than 100% dedicated protection alone Hybrid Mesh Restoration/Dedicated Protection Bandwidth Cost 100 90 Dedicated 80 Topology A 70 Topology B 60 Relative Cost Topology C 50 40 500 1000 1500 2000 2500 3000 Optical Reach At 3000km optical reach, hybrid mesh restoration with Topology C bypass and 13% dedicated protection is least expensive solution Optimized Hybrid Restoration Link Costs Fixed Costs were assumed

  20. Hybrid Designs with 1500km Optical Reach Post-Optimization Hybrid restoration 100% mesh restoration 2.80 100% 1+1 Dedicated Protection 2.60 2.40 2.20 Starting with an express topology enables more cost-effective mesh restoration, reducing need to move demands to dedicated protection 2.00 Topology A Spare Bandwidth 1.80 Moving many demands to dedicated protection significantly improves traditional mesh economics 1.60 Topology B Topology C 1.40 1.20 1.00 40 50 60 70 Fixed Costs were assumed Relative Cost Costs normalized so that 100 = cost of mesh restoration design with no optical bypass (Topology A)

  21. Hybrid Designs with 3000km Optical Reach Post-Optimization Hybrid restoration 100% mesh restoration 2.80 100% 1+1 Dedicated Protection 2.60 2.40 2.20 With express OXC topology, 3000km reach allows for flexibility in amount of dedicated protection used in cost-effective network 2.00 Spare Bandwidth 1.80 1.60 Topology A Topology C 1.40 Topology B 1.20 1.00 40 50 60 70 Fixed Costs were assumed Relative Cost Costs normalized so that 100 = cost of mesh restoration design with no optical bypass (Topology A)

  22. Hybrid Protection Cost ImprovementsFixed Cost Comparison 180 160 500km reach 140 120 100 Normalized Protection Cost 1500km reach 80 60 40 3000km reach Minimum Cost Design with 13% Dedicated Protection 20 0 0 10 20 30 40 50 60 70 80 90 100 Mesh restoration with no bypass Mesh restoration with optical bypass 100% dedicated 1+1 protection Mesh restoration with no bypass - optimal demands migrated to 1+1 Mesh restoration with optical bypass - optimal demands migrated to 1+1 % of Dedicated Protection Demands

  23. Hybrid Protection Cost ImprovementsMixed Cost Comparison OXC 10G port LH Tx/Rx LH Regen 1.00 1.00 1.33 ELH Tx/Rx ELH Regen 1.66 2.33 ULH Tx/Rx ULH Regen 2.00 3.00 180 160 140 LH (500km) 120 100 ELH (1500km) Normalized Protection Cost ULH (3000km) 80 60 Combined LH/ELH/ULH 40 Cost of Optimized ULH-only Network is Insensitive to Choice of Protection/Restoration Mechanisms 20 0 0 10 20 30 40 50 60 70 80 90 100 % of Dedicated Protection Demands

  24. Interesting Results From Other Studies

  25. Post-Optimization Hybrid protection 100% mesh restoration 2.80 Original 1+1 Design 1+1 Design for Optimized Grooming 2.60 2.40 2.20 2.00 Spare-to-Working Ch-km Ratio 1.80 1.60 Topology C Topology B 1+1 Grooming 1.40 Topology B Topology A 1.20 1.00 40 50 60 68 32 Relative Protection Cost Costs normalized so that 100 = cost of mesh protection design with no optical bypass (Topology A) Optimizing for ULH and 1+1

  26. Topology optimized for optical reach achieves both flexibility and low cost 51% DP 23% DP WS 51% WS 72% WS IP 10G Port = 2 WDM TxRx = 1 Regen = 2 No Express Links Many Express Links DRCN 2003 Optimal Link FRR vs. Hybrid (FRR and Ded. Prot. w/ and w/o Wavelength Switching)with ULH

  27. Summary • All-Optical Networks (with ULH and optical bypass) are known to make 1+1 protection architectures attractive • Much better than traditional mesh restoration • Bandwidth inefficient but cost-competitive with all single-technology restoration architectures • Results of this study show that optical bypass provides significant cost savings for the spare bandwidth in mesh restoration architectures with little loss in efficiency • Better yet, combining 1+1 with mesh restoration reduces cost even more, with attractive benefits for future MPLS/GMPLS networks • With ULH, carriers thus have great flexibility in how they provide service availability and bandwidth efficiency • Grooming should be optimized for the technology and protection mechanisms used in the network

  28. THE END

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