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Case for Segment Protection or Local Repair

This presentation by M. Vinod Kumar discusses segment protection (SPS-TE) strategies essential for ensuring network reliability, especially in the context of frequent outages caused by factors such as misconfiguration and fiber cuts. With data highlighting that India faces an alarming rate of approximately 10,000 cuts annually, the talk covers models for N:1 protection schemes, rapid switching mechanisms, and the challenges faced by service providers. The emphasis is on dynamic provisioning of protection segments to enhance network utilization and minimize service disruptions, supported by practical examples and statistics.

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Case for Segment Protection or Local Repair

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  1. Case for Segment Protection or Local Repair M Vinod Kumar Tejas Networks IEEE Interim, Seoul, Sept 08

  2. Agenda • Statistics • Few Problem Statement • What else can be taken care of? • Other benefits • Working of SPS-TE

  3. Impact of Outage Times

  4. Reason for Service Outage • Misconfiguration: Easily corrected • Resource failure: Major cause of outage • Fiber cut: • 100 to 1000 times frequent than node failure • Metro – 13 cuts every 1000 mile per year • Long Haul – 4 cuts every 1000 mile per year • Node failure: • Software • Hardware

  5. Fiber cut in USA, 1993 Cumulative Source: FCC

  6. Diagnosis of 1993 fiber cuts in US 60% Dig-ups Source: D. Crawford, 1993

  7. Now consider India • 10000 cuts per year! Annual Addition

  8. Real Failure Numbers • With over 4,00,000 (4 lakh) rings, Indian Service Providers report multiple fiber cuts per day. • Provider-A report 15 planned cuts and 5 unplanned cuts per days • Provider-B report 8 cuts per day on an average • Service Providers know that certain links are more prone than others • Up-coming area • Rain/Flood/Rodent prone area

  9. What About Other Countries? • All developing countries face similar problems that developed countries faced 10 years ago.

  10. x To Router (Dual Home) x x Regional Aggregation x x x Metro Aggregation x x Access N:1 Requirement Aggregation nodes subtends multiple and diversely routed aggregation rings Aggregation node subtends multiple access ring Access ring is getting smaller

  11. Requirements from Indian Service Provider Translated to Qay Requirements • Segment Protection models must include N:1 and should include 1:N and M:N including priority/pre-emption . • In case of 1:N model, higher priority tunnels/I-SID can pre-empt lower priority tunnels/I-SID, if required • In case of N:1 model, multiple segments can have priorities P1, P2, P3, P4 depending on the degree of protection switching needed. Typical carrier wants very fast switching (sub-50ms) of the traffic along pre-provisioned segment/path for degrees ranging between 3-10 • N:1 protection is like static routes for specific DA/VID combination with priorities P1, P2, P3 and P4 etc. In the event of the failure of P1 segment, traffic (DA/VID and associated I-SIDs) switches to P2 segment, provided it is ENABLED (Administrative Control) and healthy (Status = UP), otherwise move the traffic to P3.

  12. Working of Segment Protection… IEEE Interim, Seoul, Sept 08

  13. Present Scheme: Link Protection BEB#2 BEB#1 BCB BCB1 BCB2 TESI#1 BEB#4 TESI#2 BEB#3 • Single link failure between BCB1 and BCB2 can result in multiple TE protection switchover • In practice, many ESPs may be sharing a set of link (s) or/and node (s) BCB3

  14. Proposed: Segment Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 TESI#1 TESI#2 BEB#3 Have end-to-end protection along with local protection BCB3

  15. Present Scheme: Group Failure BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 BEB#3 BCB3

  16. Proposed: Segment Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 TESI#1 TESI#2 BEB#3 Have end-to-end protection along with local protection BCB3

  17. Present Scheme: One Link-disjoint Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 BEB#3 BCB3

  18. Proposed: Segment Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 BEB#3 Inefficient to do global switching when there is cut Have end-to-end protection along with local protection BCB3

  19. Present Scheme: Local Node Failure ESP#1 ESP#2

  20. Proposed: Segment Protection ESP#1 ESP#2 Bypass a node or multiple nodes/links by properly configuring the MD and MEPs

  21. Segment Protection in P-to-MP case p-to-mp TESI The tree branch can be protected independently

  22. Segment Protection Can Scale to Multiple Domains MD#A MD#B • MD#C ESP#1 ESP#2 • PBB-TE (Qay) TESI as segments for Domain level protection

  23. Summary: Requirements • Segment Protection Switching (SPS) shall offer n:1 • SPS should support m:n protection • Segment faults should be repairable through priority module • Priority module should take outage time impact into consideration • Segments shall be provisioned and dynamic after all provisioned segment fails • SPS should increase network utilization • Segment protection should prevent re-tracking of service • SPS should report if fault is on left or right side of the segment • SPS must tell if fault is in a service, collection of service, all the services, work segment or protect segment • Include explicit link failure along the Primary Segment • Include forwarding failure on a transit node along the Primary Segment. • Overlapping of Multiple segments should be allowed • Nesting of Segments should be allowed • SPS is more generic than IEEE 802.1Qay PBB-TE

  24. Clarification on N:1 • Use pre-provisioned protection segments for rapid 50ms protection upto 3:1 • Use dynamic protection after 3:1 fails • Combination of pre- and dynamic provisioned protection segments

  25. Thanks

  26. Extra…

  27. Working of SPS-TE • Link to SPS-TE

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