Wavelength Band Switching
in Multi-granular All-Optical
Networks
Xiaojun Cao
In collaboration with
Yizhi Xiong, Vishal Anand and Chunming Qiao
LANDER, CSE Department
SUNY at Buffalo
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Outline
Concept of wavelength band switching
(WBS)
’ Integer linear programming (ILP) model
for WBS.
’ Heuristic algorithms for WBS
’ Simulation results
’ Conclusion
’
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Wavelength Band Switching
’
’
’
’
A new WDM switching hierarchy
To reduce port count and its associated complexity in
Optical cross-connect nodes (OXC)
Use WBS in conjunction with a multi-granular OXC,
MG-OXC
Wavelength band: a group of several wavelengths
A
C
B
A
λ
λ10
λ2
λ3
D
Band of 4 wavelengths
C
B
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Multi-granular optical crossconnect (MG-OXC)
Wd r o p
.
.
.
.
Fd r o p
.
.
.
.
WXC
.
.
.
.
BTW WTB
Bdrop
.
.
Wa d d
.
.
.
.
WXC
Layer
Ba d d
.
.
BXC
.
.
.
.
FTB BTF
FXC
.
.
BXC
Layer
Fa d d
.
.
FXC
Layer
Architecture of an MG-OXC
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Classification of WBS
WBS Schemes
Fixed # B
Fixed # W
Variable # B
Variable # W
Fixed # W
Variable # W
(6)
Fixed
λ set
Arbitrary
λ set
Consecutive
(1)
(4)
Consecutive
(2)
λ set
Random
λ set Random λ set
(5)
Consecutive
(7)
λ set
Random
λ set
(8)
λ set
(3)
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Waveband assignment
strategies
(1) grouping the lightpaths with the same sourcedestination pair only;
(2) grouping the lightpaths from the same source
only;
(3) grouping the lightpaths with same destination
only;
(4) grouping the lightpaths with common
intermediate links (from any source to any
destination).
’ Strategy (4) is the most general
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ILP model for WBS
Based on waveband assignment strategy
(4).
’ Objective: minimize the total number of
MG-OXC ports in the network.
’ ??For more detail, we referred to our
original paper.
’
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Heuristic Algorithms
Waveband Oblivious (but optimal) RWA
(WBO-RWA)
’ Balanced Path with Heavy-Traffic first
waveband assignment (BPHT)
’
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WBO-RWA
’
’
’
Use ILP formulations for traditional RWA
that minimize the total number of used
wavelength-hop (WH).
Then group the assigned wavelengths into
bands and calculate the number of required
ports.
The grouping is done as an afterthought,
completely oblivious to the existence of
wavebands
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BPHT
1.
2.
Load Balanced Routing
Wavelength Assignments
A.) First, consider all traffic with path length or hops (hp>=2)
’ Define a set Qsd for every node pair (s,d), which includes
all its subpaths. Calculate weight for each set
’ Starting with Largest weight set,
1.
2.
3.
4.
Wsd = ∑hp *Tp
assign wavelengths to traffic s->d,
p∈Qsd
assign wavelengths to traffic from s
assign wavelengths to traffic to d
Recursively assign wavelengths, until all sub-paths are
assigned
B.) Finally, consider the one-hop traffic.
3.
Waveband Switching
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BPHT example
S0
4
S1
S2
2
3
S3
1
S4
6
d = S5
5
W sd =
∑h
p∈Q sd
p
S5
× t p = 5 × 1 + 4 × 1 + 3 × 1 + 2 × 1 + 4 × 1 + 3 × 1 = 21
b0
S0
b1
S1
λ4
λ3
S2
λ5
λ2
S3
λ1
λ0
S4
S5
b2
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Network Topology
6
5
1
4
3
2
11
12
1
5
2
3
9
8
4
13
14
7
10
6
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Performance Evaluation
’
Performance Metrics
– Total port number ratio T(a):
Total ( FXCn + BXCn + WXCn )u sin g WBS a lg orithm ' a '
Total (OXCn ) of ordinary − OXC
– Max port number ratio M(a):
Max( FXCn + BXCn + WXCn )u sin g WBS a lg orithm ' a '
Max(OXCn ) of ordinary − OXC
– Used wavelength channels ratio W(a):
λ − hop used by WBS a lg orithm ' a'
λ − hop used by optimal RWA without WBS
– ??Improvement in number of ports is: 1-T(a)
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Simulation Results I
’
Results for the six-node network
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Simulation Results II
’
Results of the NSF network—Random traffic
W*B=120 (number of wavelengths per fiber)
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Simulation Results III
’
Results of the NSF network—Uniform traffic
– B=30, W=4
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Conclusion
’
’
’
’
’
We explore the advantage of WBS, and intelligent
WBS heuristics.
Developed ILP formulations and heuristics to
consider the efficient design of MG-OXC optical
networks.
Intelligent WBS heuristics (such as BPHT) can
save considerably on port count.Bad heuristics
such as WBO-RWA may need even more ports
than ordinary-OXC network.
Waveband granularity (i.e. band size) has a large
effect on the performance.
There is a trade-off between wavelength-hop used
and the total port count in MG-OXC network.
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