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

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 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.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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 span failure 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

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 4 “multi-QoP” service paradigm : gold Assured single-failure restorable (R1 service) Define the following “multi-QoP” service paradigm : silver Best-efforts restorability bronze Unprotected service (economy) Preemptible unprotected service Gold and silver may both preempt economy service capacity but silver only does so after all of gold’s requirements are met.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 6 Now consider the following “multi-QoP” service mix: (economy) gold 55 % 15 % 30% silver bronze

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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%)

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 11 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Conventional “all gold” design “working” “spare”

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 12 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 55, 15,30 mix “gold” “silver” “economy” true spare capacity

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 13 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 15,30,55 mix “gold” “silver” “economy” true spare capacity

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 14 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 30,55,15 mix “gold” “silver” “economy” true spare capacity

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 15 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) 55,30,15 mix true spare capacity

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 16 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Restorability of “gold” class (always 100%)

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 17 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Best efforts restorability of silver class (~45%) (~98%) (~10%) (~15%)

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 18 Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Proportions of gold and silver restorability derived from economy

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 20 But there can be another Service Class as well.. Platinum gold silver bronze (economy) Prior QoP paradigm Assured dual-failure restorable (“R2”) service

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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. We call this strategy First failure protection, second failure restoration or “1FP-2FR” for short. ~ 200 to 500 ms < 2 seconds

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 22 Prior Finding of High Dual-failure Restorability in Networks Designed for Single Failure Protection / Restoration % R 1 (Single failure restorability) R 2 (Dual failure restorability) Between 50 % and 99 % R2(i j) on individual scenarios 70 % to 90 % network average R2 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)

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 23 Implications... Any first failure that affects your service path: R1 = 1 (by design) Any second failure that affects your service path: R2 = 1 as well ! (by priority access to a non-zero partial R2 recovery) AND... Imagine that you have a “platinum service” path through a network operating with 1FP-2FR.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 24 Such a class of Priority service in a mesh-restorable network get better than 1+1 APS availability APS “1FP 2FR” mesh (for a priority path) Normal First failure -> protection Second failure -> outage R2(ij) =0 Normal First failure -> protection Second failure -> restoration ! (adaptive) no outage yet R2(ij) >0 “Takes a licking and keeps on ticking” :-)

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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.

Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 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 [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 , pp (view paper)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 (view paper)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)