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Loop-Free Alternates and Not-Via Addresses: A Proper Combination for IP Fast Reroute?

Loop-Free Alternates and Not-Via Addresses: A Proper Combination for IP Fast Reroute?. Rüdiger Martin, Michael Menth , Matthias Hartmann University of Wuerzburg Germany. Amund Kvalbein, Tarik Cicic Simula Research Laboratories Norway. IETF 70, Vancouver, Canada RTGAREA Meeting. Overview.

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Loop-Free Alternates and Not-Via Addresses: A Proper Combination for IP Fast Reroute?

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  1. Loop-Free Alternates and Not-Via Addresses:A Proper Combination for IP Fast Reroute? Rüdiger Martin, Michael Menth, Matthias Hartmann University of Wuerzburg Germany Amund Kvalbein, Tarik Cicic Simula Research Laboratories Norway IETF 70, Vancouver, Canada RTGAREA Meeting

  2. Overview • Qualitative comparison: loop-free alternates (LFAs) vs. not-via addresses • LFAs • Taxonomy • Appropriate usage for different protection levels • Combined usage of LFAs and not-vias • Availability of LFAs for different protection purposes • Paths prolongation • Decapsulation load from tunneled not-via traffic • Conclusion

  3. LFAs and Not-Vias: Qualitative Comparison

  4. Combined Use of LFAs and Not-Vias • Not-vias • Coverage of 100% single failures • More elegant and powerful • LFAs • Readily available in today‘s routers • No tunneling • MTU issues • Performance issues on old hardware • Operators just don‘t like it • Idea to achieve 100% failure coverage • Use LFAs where possible • Use not-vias where needed

  5. Classification of Neighbors wrt a Destination Neighbor nodes of router can be classified into Nodes protecting link and node failures ECAs Downstream LFAs Non-downstream LFAs Nodes protecting only link failures ECAs Downstream LFAs Non-downstream LFAs Nodes leading to loops when traffic is sent to (7) LFC DSC ECA 7 All neighbors 6 NPC 3 General LFAs 5 2 NPC Downstream LFAs NPC 1 4 Equal-cost alternate

  6. All neighbors General LFAs LFC Downstream LFAs DSC Equal-cost alternate ECA LFAs and Not-Vias: Combination Options • Protection levels (i) Protection against all single link failures(1), (4), (2), (5), (3), (6), and not-via 7 6 NPC 3 5 2 NPC NPC 1 4

  7. LFAs and Not-Vias: Combination Options Protection levels (i) Protection against all single link failures(1), (4), (2), (5), (3), (6), and not-via (ii) Protection against all single link and all single node failures(1), (2), (3), and not-via; (4), (5), and not-via for last link All neighbors General LFAs LFC Downstream LFAs DSC Equal-cost alternate ECA 7 6 NPC 3 5 2 NPC NPC 1 4

  8. LFAs and Not-Vias: Combination Options Protection levels (i) Protection against all single link failures(1), (4), (2), (5), (3), (6), and not-via (ii) Protection against all single link and all single node failures(1), (2), (3), and not-via; (4), (5), and not-via for last link (iii) Protection against all single link and all single node failures with loop avoidance in the presence of multi-failures(1), (2), and not-via; (4), (5), and not-via for last link All neighbors General LFAs LFC Downstream LFAs DSC Equal-cost alternate ECA 7 6 NPC 3 5 2 NPC NPC 1 4

  9. 1 13 5 3 2 4 15 6 17 10 9 7 11 18 0 8 14 12 16 Applicability of LFAs and Not-Vias GEANT: resilience requriement (i): only link protection • 0-80% not-vias required • All ECAs link- & node- protecting • No other dwnstrm LFAs

  10. 1 13 5 3 2 4 15 6 17 10 9 7 11 18 0 8 14 12 16 Applicability of LFAs and Not-Vias GEANT: resilience requriement (ii): link and node protection • 20-100% not-vias required

  11. 1 13 5 3 2 4 15 6 17 10 9 7 11 18 0 8 14 12 16 Applicability of LFAs and Not-Vias GEANT: resilience requriement (iii): link, node protection, loop avoidance for multi-flrs • 20-100% not-vias required

  12. 1 13 5 3 2 4 15 6 17 10 9 7 11 18 0 8 14 12 16 Path Prolongation GEANT (protection of link & node flrs, loop avdnce for mltflrs) (protection of only link failures)

  13. Decapsulated Traffic from Not-Via Tunnels GEANT

  14. Conclusion • Classification of LFAs • Combined usage of LFA and not-via to achieve 100% failure coverage • Applicability of LFA types depends on desired protection level • Availability of applicable LFA types to protect a dest depends on • Topology and position of node in the network • Desired protection level • Backup path length • Longer with IPFRR than with IP reconvergence • Small difference between combined usage and not-vias only • Decapsulated traffic with combined usage and not-vias • Less in many cases • Maximum about the same • Same link utilization for both mechanisms (not shown) • LFAs attractive as a short-term solution

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