Factors Affecting the Efficiency of Demand-wise Shared Protection
Brian Forst, Wayne D. Grover
Contact: [email protected], [email protected]
Electrical and Computer EngineeringUniversity of Alberta2nd Floor, 9107 – 116 StreetEdmonton, Alberta, Canada T6G 2V4
Network Systems GroupTRLabs7th Floor, 9107 – 116 StreetEdmonton, Alberta, Canada T6G 2V4
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
OverviewOverview
• Background– 1+1 APS– DSP
• Methodology & Network Families• Design Results• Practical Methods to Increase Efficiency• Conclusion
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
OverviewOverview
• Background– 1+1 APS– DSP
• Methodology & Network Families• Design Results• Practical Methods to Increase Efficiency• Conclusion
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
1+1 Automatic Protection Switching (APS)1+1 Automatic Protection Switching (APS)
• Oldest and simplest protection architecture• Minimum 100% redundancy• Fastest protection
A BXWorking path
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
Why Demand-wise Shared Protection (DSP)?Why Demand-wise Shared Protection (DSP)?
• Renewed interest in 1:N DP APS as a network protection architecture
• Promising aspects include:– Fast failure-response times– Full pre-failure cross-connection of backup paths– No fault localization required– Conceptually simple to understand– Technically possible to operate in current networks– Possibility of low redundancy/high efficiency protection
• Motivation for this study:– In recent studies DSP is not exhibiting the low redundancy we
expected it could achieve
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
DSPDSP
A B
Working paths
1ab
ab
ds
k
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
DSPDSP
A B
X
1ab
ab
ds
k
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
DSPDSP
A BX
1ab
ab
ds
k
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
OverviewOverview
• Background– 1+1 APS– DSP
• Methodology & Network Families• Design Results• Practical Methods to Increase Efficiency• Conclusion
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
MethodologyMethodology
• Obtain DSP and APS design results– Hop-based costs– Distance-based costs
• Analyze route-cost statistics
• New ILP model and method to calculate route-cost statistics
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
Network TopologiesNetwork Topologies
• Two families of networks:
• Degree 3
• Degree 4
America Europe Germany
15 Node 20 Node 25 Node
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
OverviewOverview
• Background– 1+1 APS– DSP
• Methodology & Network Families• Design Results• Practical Methods to Increase Efficiency• Conclusion
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
Design ResultsDesign Results
• Hop-based costs– Degree 3 Networks: 1%, 1% and 7% savings relative to APS– Degree 4 Networks: 11% - 12% savings relative to APS
• Distance-based costs– Degree 3 Networks: 0.3%, 2.5% and 5.5% savings relative to APS– Degree 4 Networks: 8% - 9% savings relative to APS
• Here, hop-based costing gives greater reductions
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
OverviewOverview
• Background– 1+1 APS– DSP
• Methodology & Network Families• Design Results• Practical Methods to Increase Efficiency• Conclusion
15
October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
What to do?What to do?
• Small savings over 1+1 APS found– Nowhere near SBPP values.
• Six areas of concern have been identified
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
1: Average Network Nodal Degree1: Average Network Nodal Degree
• Degree 4 networks have higher savings than degree 3– Greater amounts of disjoint routes
0%
10%
20%
30%
40%
50%
60%
70%
2 3 4 5 6Number of Disjoint Routes
Pro
port
ion
of D
isjo
int R
oute
s Degree 3 GroupDegree 4 Group
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
2: Demand Splitting Restrictions (Magnitude)2: Demand Splitting Restrictions (Magnitude)
• Integer amounts of demand– Cannot be further sub-divided
BAdAB = 2
BAdAB = 1
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
3: Demand Splitting Restrictions (Divisibility)3: Demand Splitting Restrictions (Divisibility)
APS DSP
dAB = 3 BA
w1 = 3
s = 3
Cost = 6
BA
w1 = 2
s = 2
w2 = 1
Cost = 5
dAB = 4 BA
w1 = 4
s = 4
Cost = 8
BA
w1 = 2
s = 2
w2 = 2
Cost = 6
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
4: Diminishing Returns of Greater Splitting4: Diminishing Returns of Greater Splitting
1ab
ab
ds
k
ab abs d2k
3k 2ab
ab
ds
50% reduction in spare capacity
4k 3ab
ab
ds
17% further reduction in spare capacity
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
5: Degree 2 Nodes and Chains5: Degree 2 Nodes and Chains
• Europe: 32% (9 of 28)• Germany: 41% (7 of 17)
• America: 15% (2 of 14)
A
1.5% Savings
6% SavingsGermany
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
5: Degree 2 Nodes and Chains5: Degree 2 Nodes and Chains
Europe Germany
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• Remember this equation?1
abab
ds
k
• We are fighting against it
• Two important ratios
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• First ratio: Rn/R1
• Approximately 600 O-D pairs in each family
Degree 3 Families Degree 4 Families
100% R2/R1 = 1.55100% R2/R1 = 1.95
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• First ratio: Rn/R1
• Approximately 600 O-D pairs in each family
Degree 3 Families Degree 4 Families
100% R2/R1 = 1.55100% R2/R1 = 1.95
100% R3/R1 = 2.31 50% R3/R1 = 3.55
40% R4/R1 = 3.23 1% R4/R1 = 3.55
6% R5/R1 = 4.85 0% R5/R1 = N/A
<1% R6/R1 = 9.10 0% R6/R1 = N/A
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• Second ratio: Rn/(R1 + R2)
• R3 Case:
R1 : 2 work R2 : 2 spareCost = 2R1 + 2R2
R3 = 1 work
R1 = 1 work R2 = 1 spare
If R3 = R1 + R2
= R1 + R2 + (R1 + R2)
= 2R1 + 2R2
Cost
A BdAB = 2
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
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Freq of R3/(R1 + R2) RatioFreq of R4/(R1 + R2) Ratio
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• Second ratio: Rn/(R1 + R2)
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Freq of R6/(R1 + R2) Ratio
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Freq of R6/(R1 + R2) Ratio
Degree 3 Degree 4
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• 6 disjoint routes
BA
25 Node
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
6: Rapid Cost Increase of Higher Order Routes6: Rapid Cost Increase of Higher Order Routes
• Only 2 used in optimal solution!
AB
25 Node
First two routes: 400 kmThird route: 410 km
R3/(R1+R2) > 1
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
ConclusionConclusion
• New ILP model
• Identified important factors– Higher order route costs– Degree 2 nodes– Unit capacity (single-channel) demands
• Guideline for the application of DSP– 3-way splits
• These are new insights that give us an understanding of what limits the attainable efficiency of DSP
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October 9, 2007Factors Affecting the Efficiency of Demand-wise Shared Protection
DRCN 2007
Questions?Questions?