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MPLS WC 2014 Segment Routing TI-LFA Fast ReRoute

MPLS World Congress 2014
Segment Routing TI-LFA FRR

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MPLS WC 2014 Segment Routing TI-LFA Fast ReRoute

  1. 1. Topology Independent LFA Orange use case & applicability Stéphane Litkowski, Orange Expert Bruno Decraene, Orange Expert MPLS 2014
  2. 2. 2 TI-LFA Orange Business Service MPLS 2014 One of the largest dedicated network for business • Worldwide : • 172 countries, 900+ cities • France : • more than 2 million business clients, SMBs and companies in France IP VPN Ethernet Internet Cloud Voice & Telepresence High value: availability, security, SLA
  3. 3. 3 TI-LFA MPLS 2014 Agenda  Requirements  Topology Independent LFA  Applicability on Orange topologies  Simulation results
  4. 4. 4 TI-LFA MPLS 2014 Agenda  Requirements  Topology Independent LFA  Applicability on Orange topologies  Simulation results
  5. 5. 5 TI-LFA MPLS 2014 Why using Fast Reroute ?  Applications are more and more sensitive (VoIP, CRM, Sync, transport)  Customers do not want to rewrite or customize their applications code to handle network failures   Fast convergence is below 1sec BUT: – hard to have the same performance on all nodes – hard to maintain convergence time while network is growing
  6. 6. 6 TI-LFA FRR issue Primary path Backup path MPLS 2014MPLS 2014MPLS 2014 South East 8ms 5ms
  7. 7. 7 TI-LFA Backup 8ms MPLS 2014 FRR issue MPLS 2014MPLS 2014 FRR 33ms Primary path 5ms FRR
  8. 8. 8 TI-LFA MPLS 2014 How to improve ?  Requirements – 100% coverage link and node protection – No transient congestion – Optimal routing – Simple solution to operate and understand – Scalable solution
  9. 9. 9 TI-LFA MPLS 2014  What is the more optimal and natural path upon a failure ?  Post-convergence path from the PLR  Benefits of using Postconvergence path : – Policy compliant and optimized – Well sized – Well known D S Potential backup Path Postconvergence PathHow to use Post-convergence path for FRR ? How to improve ?
  10. 10. 10 TI-LFA Agenda  Requirements  Topology Independent LFA  Applicability on Orange topologies  Simulation results
  11. 11. 11 TI-LFA MPLS 2014 Segment Routing  Segment Routing technology may use any path without any need of signalling  Allows to use « unlimited » number of paths  Let’s simply compute Post Convergence Path and enforce it to be loopfree using SR R1 R6 R5 R2 R3 R4 D S SR Segments IP
  12. 12. 12 TI-LFA  Topology Independent LFA : – Segment Routing Fast-Reroute solution – Providing 100% coverage (node/link/SRLG) – encoding any FRR path by using Segment Routing blocks : – any Service Provider policy (LFA policy framework) – including post-convergence path as new criteria MPLS 2014 Topology Independent LFA
  13. 13. 13 TI-LFA MPLS 2014 Topology Independent LFA  Cannot use a strict only Explicit Path due to depth of segment stack  We need to compress the stack  Done by reusing rLFA/dLFA building blocks (P & Q space) S R1 R2 R3 D R4 R5 R6 MPLS MPLS MPLS MPLS 2 MPLS AdjR5 AdjR6 AdjR3 MPLS AdjR6 AdjR3 MPLS AdjR3 MPLS Primary EPC FRR
  14. 14. 14 TI-LFA MPLS 2014 Topology Independent LFA  FRR path is computed as follows : – Compute postconvergence shortest path (new SPF) – Enforce loop-freeness by : – finding a P node on the path – finding a Q node on the path after P (P and Q may be equal) – Only P to Q path would be explicit and may be additionnaly compressed using nodal segments S R1 R2 R3 D R4 R5 R6 MPLS MPLS 2 MPLS NodeR5 MPLS NodeR5 MPLS MPLS PQ S R1 R2 R3 D R4 R5 R6 MPLS MPLS 2 MPLS NodeR5 MPLS MPLS MPLS P 50 Q AdjR6 NodeR5 AdjR6 AdjR6
  15. 15. 15 TI-LFA MPLS 2014 Topology Independent LFA  Computation complexity is manageable : – P-Space comes from old Primary SPT – Q-Space needs one rSPT per nexthop – New primary SPT per local failure (link or node)  Expected depth of FRR stack : – Only 2 segments at max for link protection in symetric networks – There is always a P adjacent to a Q – A bit more for some node protection cases but we can add a second level of compression (by running new fSPFs)
  16. 16. 16 TI-LFA MPLS 2014 Agenda  Requirements  Topology Independent LFA  Applicability on Orange topologies  Simulation results
  17. 17. 17 TI-LFA Analysis on topologies : case #1 TI-LFA for path optimality Paris Paris Paris Paris STR STR Dijon Lyon Lyon Paris Lyon Poitiers Primary Backup MPLS 2014 Paris Out of transit node
  18. 18. 18 TI-LFA MPLS 2014 Analysis on topologies : case #1 TI-LFA for path optimality Paris Paris Paris Paris STR STR Dijon Lyon Lyon Paris Lyon Poitiers LFA MRT FRR path RSVP-TE link protection (1:n) Paris Out of transit node
  19. 19. 19 TI-LFA Analysis on topologies : case #1 TI-LFA for path optimality Paris 1 Paris 2 Paris 3 Paris 5 STR STR Dijon Lyon Lyon Paris 4 Lyon Poitiers EPC FRR Nodal EPC stack composed of one segment Protection stack Node_Paris4 MPLS 2014 Paris Out of transit node
  20. 20. 20 TI-LFA Analysis on topologies : case #2 TI-LFA vs LFA/rLFA MPLS 2014 PE1 P1 PE2 P2 P5 P4 P3 PE3 40 15 10k10k 20 20 20 30 39 Primary Backup 10k LFA : • PE2 is defacto node protection (not guaranteed) rLFA : • cannot guarantee node protection
  21. 21. 21 TI-LFA MPLS 2014 Analysis on topologies : case #2 TI-LFA vs LFA/rLFA SR segment EPC provides node protection with 1 segment Protection stack Node_P3 Backup PQ PE1 P1 PE2 P2 P5 P4 P3 PE3 40 15 10k10k 20 20 20 30 39 10k
  22. 22. 22 TI-LFA MPLS 2014 Analysis on topologies : case #3 TI-LFA using multiple segments PE1 R1 PE2 R2 R3 R4 R5 R6 R7 PE3 1 7 3 3 3 1 1 1 11 2 100 100 Primary Backup SR Segments Nodal to PE3 Protection stack compressed Node_R3 Node_PE3 P QProtection stack (PQ) Adj_R3 Adj_R4 Adj_R6 Adj_R7 Adj_PE3 Top Bottom Top Bottom Nodal to R3 Nodal to PE3
  23. 23. 23 TI-LFA MPLS 2014 Analysis on topologies : case #4 Maximum observed stack depth PE1 PE2 R1 R2 R3 R4 R5 R6 100 100 2 1 2 3 3 1 3 1 3 1000 P Q Protection stack (PQ) Node_R3 Adj_R4 Adj_R5 Adj_R6 Adj_PE2 Protection stack compressed Node_R5 Node_R6 Node_R3 Adj_PE2 Primary Backup SR Segments Top Bottom Top Bottom
  24. 24. 24 TI-LFA MPLS 2014 Agenda  Requirements  Topology Independent LFA  Applicability on Orange topologies  Simulation results
  25. 25. 25 TI-LFA MPLS 2014 Simulations results on 11 Orange Networks Depth of protection stack 11 topologies have been analyzed including multiple network types and size
  26. 26. 26 TI-LFA Simulations results on 11 Orange Networks Per node analysis (node protection case) MPLS 2014 92% of nodes from ALL topologies have 99% of its repair_lists with a size <=2
  27. 27. 27 TI-LFA Simulations results on 11 Orange Networks MPLS 2014 80% of nodes have 12 or less distinct repair_lists
  28. 28. 28 TI-LFA Simulations results on 11 Orange Networks Path compression : computation complexity MPLS 2014
  29. 29. 29 TI-LFA  100% FRR link/node protection is a requirement  Current FRR technics may cause some side effects : – Transient network congestion – Additionnal management for selection of the backup path  Topology Independent LFA : – Scalable : no additional state in the network – Simple to compute – Provides 100% link/node protection – Prevents any side effect by using a well sized and optimal path – Simple to understand : well known path MPLS 2014 Conclusion
  30. 30. Thank you !

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