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An Efficient Strategy for Wavelength Conversionin WDM p-Cycle Networks
Dominic A. Schupke, Matthias C. Scheffel{schupke,scheffel}@lkn.ei.tum.de
Wayne D. Grover{[email protected] }
Fourth International Workshop on the
Design of Reliable Communication Networks
(DRCN 2003)
Munich University of Technology
Institute of Communication Networks
TRLabs &
University of Alberta
21 October 2003
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Motivation
• WDM transport networks are becoming more “optical”
– Functions realized in optical domain (e.g. switching)– Routing and wavelength assignment (RWA) problem– High wavelength converter cost
Partial wavelength conversion
• Need for reliability against network failures
– Low capacity redundancy– Fast protection
p-Cycle concept
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Outline
• p-Cycle Concept
• p-Cycles in WDM Networks
– Full wavelength conversion
– No wavelength conversion
– Partial wavelength conversion
• Implementation
• Case Study Scenario
• Results
• Conclusions / Outlook
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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p-Cycle Concept
Description
• Network protection strategy
– Spans
– (Transit nodes, paths)
• p-Cycles
– Preconfigured closed paths
– Reserved capacity
– In mesh network
B E
C
A
Dp-Cycle
Node
Span
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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p-Cycle Concept
Span Protection Mechanism
– On-cycle span
• Span is used by p-cycle
B E
C
A
Dp-Cycle
Protection path
Node
Span
1 protection path
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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p-Cycle Concept
Span Protection Mechanism
– On-cycle span
• Span is used by p-cycle
– Straddling span
• Span’s end nodes lie on p-cycle
• Span is not used by p-cycle
B E
C
A
D
2 protection paths
1 protection path
p-Cycle
Protection path
Node
Span
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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p-Cycles in WDM Networks
Full Wavelength Conversion at Nodes
• Different wavelengths along a path
• Termination of paths at each node
Virtual Wavelength Path VWP
p-Cycle can protect working links
at any wavelength
+ Capacity-efficient protection
– High converter cost
B E
C
A
D
p-Cycle
Working path
Wavelength links
Full conversion
netVWP Approach
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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p-Cycles in WDM Networks
No Wavelength Conversion at Nodes
• Same wavelength along a path
• No termination along paths
Wavelength Path WP
p-Cycle can protect working links
at same wavelength only
+ No converter cost– More capacity redundancy
B E
C
A
D
p-Cycle
Working path
Wavelength links
No conversion
netWP Approach
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Partial Wavelength Conversion at Nodes
• Converter Pool with tunable lasers
• Wavelength conversion for some paths
• Termination of some paths
• Idea:
Make p-cycles accessible
for working links at different wavelengths
by providing a small number of converters
p-Cycles in WDM Networks
B E
C
A
D
Partial conversion
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
10
p-Cycles in WDM Networks
A
E
D
C
B
Working paths without conversion
Working WP
p-Cycles without conversion
p-Cycle WP
Converters for p-cycle access
Partial Wavelength Conversion at Nodes
wWP_pWP_accessIfRequired &wWP_pWP_accessFull Approach
• If Required
• Full
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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A
E
D
C
B
p-Cycles in WDM Networks
p-Cycles with full conversion
p-Cycle VWP
Working paths without conversion
Working WP
Partial Wavelength Conversion at Nodes
(+ straddling span converters)
wWP_pVWP Approach
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Implementation
Mathematical Programming
Integer linear program (ILP)
• Objective function:
Minimize ( ∑ working path lengths +
∑ p-cycle lengths +
number of converters • converter cost )
• Constraints:
(1) Provide WP working paths to satisfy the demands
(2) Allocate p-cycles to provide protection for any single span failure
(3) Insert converters according to architecture
(4) Use one wavelength at most once per fiber
Joint optimization of working and protection capacity plus total converter cost
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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COST239 Network
• Pan-European
optical core network• 11 nodes, 26 spans• Average nodal degree = 4.7• 1 counterdirectional fiber pair
per span• 32 wavelengths per fiber• Given demands
– Dense matrix– 1 to 11 lightpaths per node
(average = 3.2) – Symmetry modification
Case Study Scenario
Copenhagen
LondonAmsterdam Berlin
Paris
BrusselsLuxembourg
Prague
Vienna
Zurich
Milan
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Results
Total Cost Comparison
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
0 100 200 300 400 500 600
Converter cost (in link-km)
To
tal
cost
(in
lin
k-km
)
netWP
wWP_pVWP
wWP_pWP_accessFull
wWP_pWP_accessIfRequired
netVWP_fullyEquipped
netVWP_partiallyEquipped
fullyEquipped = converters for any available wavelength
partiallyEquipped = converters for used wavelengths only
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Results
Capacity-Efficiency Evaluation
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 100 200 300 400 500 600
Converter cost (in link-km)
Cap
acit
y-ef
fici
ency
netWP
wWP_pVWP
wWP_pWP_accessFull
wWP_pWP_accessIfRequired
netVWP
Capacity-efficiency =protection capacity
working capacity
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Results
Wavelength Converter Allocation
0200400600800
10001200140016001800
0 100 200 300 400 500 600
Converter cost (in link-km)
Nu
mb
er o
f co
nve
rter
s
netWPwWP_pVWPwWP_pWP_accessFullwWP_pWP_accessIfRequirednetVWP_fullyEquippednetVWP_partiallyEquipped
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Conclusions / Outlook
• Conclusions:
p-Cycle configurations
in WDM networks with partial wavelength conversion
can reduce the total network cost
– Capacity-efficient protection• Small amount of redundant capacity• More flexibility towards changing demand patterns
– Small number of converters
• Outlook:
Performance evaluation of online routing and protection
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Technische Universität München Institute of Communication NetworksProf. Dr.-Ing J. Eberspächer
Matthias C. ScheffelDRCN 2003
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Comparison of p-Cycle Configurations
netVWP
wWP_
pWP_
accessIf
Required
wWP_
pWP_
access
Full
wWP_
pVWPnetWP
Protection efficiency
highest high very high high very low
Converters most very few few more no
Tunable lasers required
no yes yes yes n/a
Termination of protection paths
yes some yes yes no
Wavelength flexibility
highest low high higher n/a