Design Method of Logical Topologies in WDM Network
with Quality of Protection
Junichi Katou
Dept. of Informatics and Mathematical Science,
Graduate School of Engineering Science,
Osaka University
[email protected]
11/02/2001
Workshop on Optical Networking
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Background
• Protection : backup paths are prepared for each primary
lightpath for recovery from a failure
• Many researchers have proposed several logical topology
design algorithms with protection.
– example objective：minimize # of wavelength、minimize the blocking rate
• few research mention the quality of protection
QoP (Quality of Protection)
one realization of QoS suitable to the WDM network
QoS for failure tolerance
Dr. O. Gerstel propose probability-based QoP
SLSP (Short Leap Shared Protection)
Dr. Pin-Han. Ho propose a protection method
he propose new QoP based on the length of protection paths
11/02/2001
Workshop on Optical Networking
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SLSP : Short Leap Shared Protection
SLSP Sample Model
configure the length of
protection paths by
selecting the end nodes for
each protection path to
satisfy the required QoP
Original SLSP
require QoP to determine the maximum length of
protection paths for each primary lightpath
Our Proposal
set QoP as a QoS to determine the maximum recovery
time for each primary lightpath
propose logical topology with SLSP design algorithm
which can deal with our proposed QoP
11/02/2001
Workshop on Optical Networking
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Recovery time modeling
Dnode Dnode Dnode
Dconf
Protection Path Px : ｈ hops
m-1 m m+1
n-1
n
n+1
propagation delay of the segment covered by Px : Dp
Recovery time of segment (m, n) =
Dp Maximum failure detection time
+
Dnode×ｈ
path configuration time
+
Dconf
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Workshop on Optical Networking
path switching time
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Proposed QoS considering recovery time
Each path connection between node pairs require QoP
For all segment(m,n) of primary path
QoPn
Recovery time of segment (m, n)
Dmin+ (n-1)×Dscale
Dp + Dnode×ｈ + Dconf
Dmin：minimum waiting time to recover from a failure
Dscale : step-width of the recovery time
be determined properly for each network environment
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Workshop on Optical Networking
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First Fit wavelength assignment method
available Wavelength
not available Wavelength
assign
not available
λ0
paths to the
assignable wavelength with
the smallest index of λ
assign
available
λ1
available
λ2
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Workshop on Optical Networking
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Max Share wavelength assignment method
newly-used W
shared W
cost
２
assign paths to maximize
the number of shared
wavelength cannel by
protection paths
λ0
assign
０
λ1
Cost : the number of
newly-used wavelength
cannel by protection paths
１
λ2
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Workshop on Optical Networking
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proposed Logical Topology Design Algorithms
Propose 2 Algorithms
Protection Method
both algorithms use SLSP
Routing of primary and protection path
both algorithms use shortest path between
each each node pair for primary lightpath
both algorithms use shortestpath between
selected end nodes for protection path
Wavelength Assignment Method
Algorithm 1 use First Fit
Algorithm 2 use Max Share
11/02/2001
Workshop on Optical Networking
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Evaluation Model
Network model ： NSFNET(14nodes, 21links)
Traffic matrix ： 0.1-20.0Gbps real traffic trace value
Wavelength capacity ： 10Gbps / wavelength
QoP ： set 1 to ∞ for each node pair
Performance metric ： # of necessary wavelengths
Dmin
minimum waiting time for the recovery
Dscale step-width of the QoP
Dnode path configuration time at each node
Dconf path switching time
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Workshop on Optical Networking
10ms
2ms
1ms
0ms
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Evaluation1 : QoP vs # of necessary wavelengths assigned by First Fit
QoP requirement for each node pairs is set identically
the number of necessary
wavelengths is
decreasing according
to the decreasing of the
QoP level
fixed at low QoP
dropping at QoP4 and
not showing simple
decrease at high QoP
# of necessary Wavelength
60
50
40
30
20
10
0
2
4
6
High QoP
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Workshop on Optical Networking
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10 12 14 16 18
QoP: Quality of Protection
20
Low QoP
10
Evaluation1 : the reason for the dropping of the # of necessary wavelengths
There are some node pairs not to satisfy the required QoP
45
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35
# of blocking
REASON
lack of route for
protection path which is
enough short to satisfy
the required QoP
we call this blocking
In this case, only
primary path is set up
30
25
20
15
10
5
0
2
4
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10
12
14
16
QoP: Quality of Protection
18
11
20
Evaluation2 : comparison of two wavelength assignment method
randomly set QoP requirement for each node pairs
given traffic ： traffic matrix multiplied by α
1000
proposed
algorithm 2
needs less # of
wavelengths
algorithm
2 tries to
share wavelength by
more protection paths
than algorithm 1
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# of Wavelength
900
800
First Fit
700
600
500
400
300
Max Share
200
100
0
10
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30
40
50
Traffic scale α
60
70
12
80
Conclusions and future works
 Conclusions
– propose QoP considering the recovery time form failure
– propose two logical topology design algorithms with QoP
– show the relationship between QoP and the number of
necessary wavelengths
– algorithm 2 show effective utilization of wavelengths
 Future works
– evaluations under non-blocking condition
– to gain the performance by changing the routing of paths
– to design logical topology applying the behavior of upper layer
protocol (e.g. IP)
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Workshop on Optical Networking
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