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Mesh Restorable Networks with Multiple Quality of Protection Classes

Mesh Restorable Networks with Multiple Quality of Protection Classes. Wayne D. Grover, Matthieu Clouqueur grover@trlabs.ca, clouqueur@trlabs.ca TR Labs and University of Alberta Edmonton, AB, Canada ICOCN 2002, November 11-14, Singapore. Motivation and Background.

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Mesh Restorable Networks with Multiple Quality of Protection Classes

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  1. Mesh Restorable Networks with Multiple Quality of Protection Classes Wayne D. Grover, Matthieu Clouqueur grover@trlabs.ca, clouqueur@trlabs.ca TRLabs and University of Alberta Edmonton, AB, Canada ICOCN 2002, November 11-14, Singapore

  2. Motivation and Background • “one grade of protection for all” doesn’t necessarily fit the customer needs or service provider wishes. • Prior work on survivable network design almost exclusively considered 100% restorable single class of service. • Now consider multiple “Quality of Protection” options. • Most important properties and insights: • Mesh restorable networks with no spare capacity • A premium service class with better than 1+1 availability • Overall design capability to support highly differentiated service classes in an economic mesh-based network.

  3. Define Some terms ... QoP - is like QoS but refers to different “Quality of Protection” service classes. R1- a class of service path that is assured of single spanfailure restorability -the average level of single failure restorability of a network as a whole R2 - a class of service path that is assured of restorability to any dual span failure - the average level of dual failure restorability of a network spare capacity - the shared but idle standby capacity of a mesh network that is used to protect services from different failure scenarios

  4. gold Assured single-failure restorable (R1 service) silver Best-efforts restorability bronze Unprotected service (economy) Preemptible unprotected service “multi-QoP” service paradigm : Define the following “multi-QoP” service paradigm : Gold and silver may both preempt economy service capacity but silver only does so after all of gold’s requirements are met.

  5. Structure of the Mathematical Model ... Minimize {total cost of capacity installed} subject to: - (a) all gold, silver, bronze and economy service demands are routed and assigned working capacity. - (b) on any span failure working capacity assigned to gold service paths is 100% restorable - (c) on every other span the sum of the spare capacity plus and economy capacity is sufficient to support the largest restoration flows needed for (b) - (optionally) working and spare capacities assigned to each span fit under a limited set of available modular capacities.

  6. gold 55 % silver bronze Now consider the following “multi-QoP” service mix: 15 % (economy) 30%

  7. Test Networks ... ..on every O-D pair in the following test networks …. Each node pair has 20 lightpath demands : 11 gold (55%), 3 silver-bronze (15%), 6 economy (30%)

  8. Main Findings ... There is no spare capacity needed. (!) • Restoration requirements for the 55% gold service class are fully met by preemption of economy class services. • Silver class services enjoy ~ 40-50% best efforts restorability. • Any given economy service path can expect to be disrupted in 12 to 14 % of all failures.

  9. Significance ... • Such network designs are “fully survivable” in the usual sense (for 55% of the customers) but there is no unused standby capacity. • --> All capacity is earning revenue at some level or other. • Such flexible, highly efficient “multi-QoP” capabilities may turn out to be the most commercially significant advantage (the “killer app”) for mesh-based transport networking.

  10. Wider Study of multi-QoP Design... Considers four multi-service demand scenarios for testing : All designs based on span restoration mechanism with hop limit of five Designs are “ jointly optimized” : (-> routing of gold and economy paths are synergistic decisions.) Mathematical model minimizes total capacity cost

  11. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Conventional “all gold” design “working” “spare”

  12. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 55, 15,30 mix true spare capacity “gold” “silver” “economy”

  13. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 15,30,55 mix true spare capacity “gold” “silver” “economy”

  14. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 30,55,15 mix true spare capacity “gold” “silver” “economy”

  15. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 55,30,15 mix true spare capacity

  16. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Restorability of “gold” class (always 100%)

  17. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) (~98%) (~45%) Best efforts restorability of silver class (~15%) (~10%)

  18. Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Proportions of gold and silver restorability derived from economy

  19. Important points... • Gold class always 100% restorable • No spare capacity perse, except with maximum imbalance of gold and economy • Best efforts restorability changes greatly depending in economy percentage • Virtually all gold & silver restoration is obtained by economy preemption • So how bad is life for the economy class services ? • Separate analyses of results shows the average economy service path faces ~ 1-in-10 to 1-in-20 chance of disruption given any other single span failure.

  20. Assured dual-failure restorable (“R2”) service gold silver Prior QoP paradigm bronze (economy) But there can be another Service Class as well.. Platinum

  21. Key Concept leading to “Platinum” Service Class... • In a mesh-restorable network it is possible to have • - a pre-planned “protection” response to any single failure • and • - an adaptive (state-dependent) “restoration” response to any dual or subsequent failure. ~ 200 to 500 ms < 2 seconds • We call this strategy • First failure protection, second failure restoration • or • “1FP-2FR” for short.

  22. 100 % Between 50 % and 99 % R2(i j) on individual scenarios 70 % to 90 % network average R2 R1 (Single failure restorability) R2 (Dual failure restorability) Prior Finding of High Dual-failure Restorability in Networks Designed for Single Failure Protection / Restoration ... In a mesh-restorable network design for R1=1 begets high R2 as a side-effect. --- > R2 is never 0% (unless at a degree-2 node)

  23. Implications ... Imagine that you have a “platinum service” path through a network operating with 1FP-2FR. Any first failure that affects your service path: R1 = 1 (by design) AND ... Any second failure that affects your service path: R2 = 1 as well ! (by priority access to a non-zero partial R2 recovery)

  24. Normal Normal First failure -> protection First failure -> protection Second failure-> restoration ! (adaptive) no outage yet R2(ij) >0 Second failure -> outage R2(ij) =0 “Takes a licking and keeps on ticking” :-) Such a class of Priority service in a mesh-restorable network get better than 1+1 APS availability ... 1+1 APS “1FP 2FR” mesh (for a priority path)

  25. Summary, Notes, and Further Work Key points: (1) Mesh-restorable networks are extremely well-suited to support multi-QoP operation and business strategies. Restoration requirements for gold can be fully met through economy preemption and / or small amounts of shared spare capacity. Over a range of service mixes no spare capacity is needed. (2) Because R1=1 implies R2 >0 for virtually all cases in a mesh restorable design, it is possible to support a “platinum” (R2=1) service class under 1F-2R operation. Such service gets better than 1+1 availability. Provisos: - economy routing complexity increased (is not shortest-path) - degree 2 nodes not applicable Further Work Direction: - Integrate design with platinum services with other QoP stack under min total cost. - Bi-criterion studies enhancing best-efforts to target levels. - Convert optimal solution models to incremental operational heuristics.

  26. To delve further … Papers available on request: [1] W.D. Grover, M.Clouqueur, “Span-Restorable Mesh Networks with Multiple Quality of Protection (QoP) Service Classes,” in review with Optical Networks Magazine, September 2002. [2] M. Clouqueur, W. D. Grover, "Mesh-restorable Networks with Complete Dual-failure Restorability and with Selectively Enhanced Dual-failure Restorability Properties," Proc. SPIE Optical Networking and Communications Conference (OptiComm 2002), Boston, July 29-Aug. 2, 2002, paper 4874-1, pp.1-12. (view paper) [3] M. Clouqueur, W. D. Grover, “Computational and Design Studies on the Unavailability of Mesh-restorable Networks,” in Proc. DRCN 2000, Munich, Germany, April 2000, pp. 181-186. (view paper) See also related presentation at Tech Forum 2002 : “Mesh Restorable Networks with Enhanced Dual-Failure Restorability Properties” (M.Clouqueur, Wed. Oct 23, FP13, Morning Session)

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