Mesh Restorable Networks with Mesh Restorable Networks with Multiple Quality of Protection Multiple Quality of Protection Classes Classes Wayne D. Grover, Matthieu Wayne D. Grover, Matthieu Clouqueur Clouqueur [email protected], [email protected][email protected], [email protected]TR TR Labs Labs and University of Alberta and University of Alberta Edmonton, AB, Canada Edmonton, AB, Canada ICOCN 2002, ICOCN 2002, November 11-14, Singapore November 11-14, Singapore
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Mesh Restorable Networks with Multiple Quality of Protection Classes Wayne D. Grover, Matthieu Clouqueur [email protected], [email protected] TRLabs and.
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Mesh Restorable Networks with Multiple Mesh Restorable Networks with Multiple Quality of Protection ClassesQuality of Protection Classes
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 ...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: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 ...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%)
(a) (b) (c)
Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 8
Main Findings ...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 ...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...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 fiveDesigns are “ jointly optimized” : (-> routing of gold and economy paths are synergistic decisions.) Mathematical model minimizes total capacity cost
economy 30%
gold 55%
silver- bronze 15%
30%
15%
55% 55%
30%
15% 30%
55%
15%
Scenario A: Mostly gold & economy
Scenario B: Most ly economy
Scenario C: Mostly best-efforts
Scenario D: Mostly gold & best-efforts
Wayne D. Grover and Matthieu Clouqueur ICOCN ‘02 Singapore 11
Sample Results (Study of multi-QoP Design...Sample Results (Study of multi-QoP Design...
Gold R1 Silv R1 Econ P(pre) Prop. Preem p. Gold Prop. Preem p. Silv
(Results for network 25n50s1)
Proportions of gold and silver restorability derived from economy
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Important points...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 But there can be anotheranother Service Class as well.. 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...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
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Prior Finding of High Dual-failure Restorability in Networks Prior Finding of High Dual-failure Restorability in Networks Designed for Single Failure Protection / Restoration ...Designed for Single Failure Protection / Restoration ...
100 %
R1
(Single failure restorability)R2
(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)
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Implications ...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 Such a class of Priority service in a mesh-restorable network get better thanbetter than 1+1 APS availability ... 1+1 APS availability ...
1+1 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 WorkSummary, 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 …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)