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Multi-layered Optical Network
Security
Hwajung Lee
Department of Information Technology
Radford University
Contents
Background
Research Goal and Three Main Results
 Survivable Optical Layer Design
 Survivable IP Layer Design
 Reconfiguration preserving Survivability
Concluding Remarks
All Optical Networks
All
Optical
Networks
Regeneration
/Adaptation
O-E-O
SONET
Terminal
IP Router
All
Optical
Networks
All
Optical
Networks
AON Security Characteristics
 Extremely high data rate
 Short and infrequent attacks or failures can
result in loss of large amounts of data.
• 1.6 Terabits per second is equivalent to 320 million
Pages/sec of information
If eavesdropping attack lasts only 1 second, 320 million
page of classified information could be compromised.
• 1.6 Terabits per second is 25 million simultaneous
telephone conversation.
If a link failure lasts only 1 second, 25 million
simultaneous telephone conversation could be disrupted.
Any Security Solutions?
Confidentiality
Integrity
 Cryptography (PKI, Digital Signature…)
Availability
 We have a security hole to fill in.
:by guaranteeing the network survivability.
Network Model: lP over WDM Network
More layers in an
overlay models
Cons
 More Redundant
functions
 Large header data
Thus, getting simpler.
IP
ATM
IP
SONET/ SONET/
SDH
SDH
IP
ATM
WDM Optical Network
IP
Terminology
 WDM : Wavelength Division Multiplexing
 Lightpath : Transfer Path from Source to Sink
in Optical Network
 Fault Propagation : Failure from a layer
propagates into other network layers.
 Logical Topology : IP layer
 Physical Topology : WDM layer
 Logical topology (Upper Layer) is called
survivable if it remains connected under an
impact of fault propagation in the presence of
a single optical link (Lower Layer) failure.
What is WDM?
Mux
Demux
Fault
Propagation
Embedding
End User
End User
R
End User End User
A
C
End User
End User
R
End User
R
B
Not Survivable
R
R
C
Cons of WDM Protection
1. Requires to reserve extra resources.
2. Can be failed.
A
Logical
Topology
B
Example of a Survivable Logical Topology
End User
End User
R
End User End User
C
End User
R
End User
R
A
End User
B
R
R
C
End User
End User
R
End User End User
End User
R
C
End User
End User
R
A
B
R
Logical
Topology
R
Survivable
A
B
Survivable Logical Topology
 Sometimes, there is no way to have a Survivable
Logical Topology Embedding on a Physical Topology.
Optical Layer
= Physical Topo.
Electronic Layer
= Logical Topology
c
e2
b
…
…
a
e1
2-Edge Connected
d
a
c
d
b
Main
Research
Result
Goal
1
Support Survivability in IP over WDM network
against a single link failure in an WDM network.
1st Problem : Design of Survivable IP over WDM Ring Networks
Logical
topology
Physical
topology
Lemma
Four Nodes
Gleft
a
c
a
c
ei
ej
Gright
b
d
b
d
... a a
...
a
ei
b
c ......
bb ......
...
... dd
c ej
d
Lemma (Cont.)
Three Nodes
Gleft
a
c
a
c
ei
ej
Gright
b
b
a
ei
... a
c ...
c
b b
...
...
ej
Lemma (Cont.)
 Suppose G is 2-edge-connected and G0 is a ring.
For any edge cut of size two {(a, b), (c, d)} in G,
nodes f(a), f(c), f(b), f(d), in this order, may not be
lay out in G0 in the clockwise or counterclockwise
direction.
Embedding Algorithm
aaa
Glleft
ee
dd
cc
ii
Grleft
l
c
h
g
bbb
Gleft
k
jj
Gleft
Grightff
b
Gright
a
ddd
f
g
h
i
cc
ee
l
hh
j
aaae
c
bbb
d
ff
gg
k
Theorem
 Given a 2-edge-connected IP topology G and
a ring network G0 as the WDM optical
network topology, there exists a mapping of G
into G0 such that G is tolerant to the failure of
any single link in G0.
Main Result 2
2nd Problem : Design of Survivable Virtual Topology in IP over WDM
Yes
Logical
topology
Does
Survivable Embedding
Exist?
Done
Physical
topology
No
Add Additional links
on
the Logical Topology
Problem Complexity
 Survivable LT design possible
 Completely connected (i.e., (n-1)-edge connected)
 NO survivable LT design when logical topology G is
 2-edge connected
 3-edge connected
 4-edged connected
 Degree Constraints
2n
 Survivable LT design possible when min. degree >= 3
n
 No survivable LT design for min. degree <= ( 2 -1)
 Experimental Results – Near Optimal
Complete Graph
: Survivable
1
1
5
2
2
5
3
4
3
4
3-edge Connected Graph
: not Survivable
C2
C1
k
a1
a2
e
a1
h
b1
k
b2
f
i
c1
b1
f
c2
g
j
d1
d2
e
b2
a2
l
C4 C3
4-edge Connected Graph
: not Survivable
b1
b3
b2
e4
b4
c1
C1
a1
b1
b3
b2
b4
e3
c3
C2
a3
c4
a4
C3
C4
a1
e1
c2
a2
e2
a3
d1
d2
d3
d4
a4
c1
d3
c2
d4
d1
e1
e2
e3
e4
d2
c3
a2
c4
Shortest Path Routing
: Survivable if (minimum d  2n )
3
si  6 +i (L); si  6 - I + n -1(R)
t: highest index in L  smallest_component
n
n
n
n
n
4 cases: t  4 -1; t  3 ; 4  t  3 -2; t= 3 -1
n
n
n/3-1
n/2-1
n/2
j
L
2n/3
n-j-1
n/4+1
n/4
R
n/2+j
0
n-1
Shortest Path Routing
n
: not Survivable if (minimum d  2 -1 )
...
: Vodd
: Veven
0
Kn/2-1 Graph 0
n-1
n-1 Kn/2-1 Graph
Heuristic Algorithm
based on Shortest Path Routing
optical link (x,y)
# of components
sets of components
={C1, C2, …}
Embed logical links
to lightpaths.
Cut each optical link
and Calculate
the # of Components.
Max # = 1
Yes
Done
No
Find an optical link (x,y)
with the maximum # of
components.
No
Add an additional lightpath
connecting a node
from Ci to a node from Cj
without using (x,y).
Numerical Results
# of Simulations = 1000
25
22.953
20
15
2 edge-connected
arbitrary
10
5
7.037
3.357
1.861
1.938
0.002
0.008
link probability p
0.
2
0
0.
02
8
0.
04
0.
06
0.
08
0.
1
average # of additional lightpaths
n = 100
Numerical Results
# of Simulations = 1000
8.889
2 edge-connected
4.632
arbitrary
link probability p
0.
2
0.
1
0.494
0.549 0.023
0.027
0.
04
0.
06
0.
08
8
10
9
8
7
6
5
4
3
2
1
0
0.
02
average # of addtional
lightpaths
n = 200
Numerical Results
# of Simulations = 1000
n = 300
10.293
9
7
5.585
2 edge-connected
5
3
1
arbitrary
0.533
0.814
0.027
0.027
-1
0.
02
8
0.
05
0.
07
0.
09
0.
11
0.
13
0.
15
average # of addtional lightpaths
11
link probability p
Main Result 3
3rd Problem : Reconfiguration of Virtual Topologies
Preserving Survivability
Survivable Embedding has been done.
Logical
topology
Physical
topology
New Survivable Embedding
New
Logical
topology
Reconfiguration of Survivable
Logical Topologies
Survivable Logical Topology = G1
Survivable Logical Topology = G2
What if # of Wavelength < 3 or # of Ports < 3
0
1
0
1
3
2
3
2
# of Ports = 3
Physical Topology = Gp
0
3
# of Wavelength = 3
1
2
Delete G1\G2
Add G2\G1
to form G1  G2
Problem Complexity
Sometimes, we need to…
 Modify the current embedding of some
lightpaths in G1  G2 .
 Temporarily delete and reestablish some
lightpaths in G1  G2 due to the wavelenth
constraint.
 Temporarily add some lightpaths not in G1 
G2 and delete to guarantee the survivability
during the reconfiguration.
Simple Reconfiguration Approach
If the current lightpath setup uses W-1 wavelength
in each optical link and upto p-2 ports at each node,
 add a lightpath btw
each pair of
adjacent nodes,
 delete all lightpaths
in G1 except the
above, and
 establish all
lightpaths in G2
based on its
survivable
embedding.
W = 4, p = 6
1
6
2
5
3
4
Limitation
of Simple Reconfiguration Approach
n-k+2
n-k+1
n-k
1
2
3
4
...
n
...
...
W = n- k + 1
MinCostReconfiguration
Cost = # of add * UnitCostadd + # of delete * UnitCostdelete
 Given Input : M1, M2, Gp
 Output : Wadd,
Wadd = Wreconfig – max{WM1, WM2}
 Constraints
the number of port p, the number of wavelength W
 Objectives
(1) To minimize Wreconfig while reconfiguration cost is
preserved minimum.
(2) During the entire period of reconfiguration,
(1) The logical topology remains survivable
(2) The port p and wavelength W constraints are satisfied.
MinCostReconfiguration
Survivable Embedding, M2,
Of G2 to GP
Wreconfig=max{WM1,WM2}
Compare M2 with the current
survivable embedding M1
and Generate ADD set and
DELETE set
Add lightpaths in ADD
as long as
not violate W constraint
Delete lightpaths in DELETE
as long as not violate
survivability constraint
ADD = ø and
DELETE = ø
Done
No
Yes
Yes
Any Addition
and Deletion
No
Wreconfig = Wreconfig + 1
Numerical Results
# of Simulations per each case = 500
n=8
DiffFactor
ofreconfig
different
conn. Req.)
W=add =(#W
– max{W
M1, WM2}
(total # of possible conn. Req.)
10%
20%
30%
40%
50%
60%
70%
80%
90%
<W ADD >
<W M1>
<W M2>
Max Min Avg
Max Min Avg
Max Min Avg
1
0 0.008
8
4 5.784
8
3 5.464
2
0 0.068
8
3 5.770
7
3 5.388
2
0 0.100
8
3 5.692
8
3 5.380
2
0 0.122
8
4 5.806
8
3 5.282
2
0 0.076
8
4 5.800
8
3 5.368
2
0 0.062
8
3 5.796
8
3 5.180
2
0 0.092
8
3 5.772
7
3 5.086
2
0 0.064
8
3 5.772
8
3 4.850
1
0 0.066
8
4 5.750
7
3 4.736
Average
8 3.4 5.771 7.7
3 5.193
# o f Diff Co nn Req. Expected # o f Diff Co nn
(fro m Simulatio n) Req.(Calculated)
1.091
2.375
3.762
5.420
6.710
8.212
9.433
10.869
12.099
1.400
2.800
4.200
5.600
7.000
8.400
9.800
11.200
12.600
Numerical Results
# of Simulations per each case = 500
n = 16
10%
20%
30%
40%
50%
60%
70%
80%
90%
<W ADD >
Max Min Avg
3
0 0.034
1
0 0.008
2
0 0.012
4
0 0.064
5
0 0.076
3
0 0.046
2
0 0.020
1
0 0.008
1
0 0.008
Average
<W M1>
<W M2>
Max Min Avg
Max Min Avg
21 10 14.588 19
8 13.360
20 11 14.668 20
7 13.026
21
9 14.698 20
7 14.330
22 10 14.726 19
9 14.586
20 10 14.528 19
9 14.536
21 10 14.610 20
9 14.426
21 10 14.624 19
6 14.182
22 10 14.594 19
7 13.158
21 10 14.506 20
9 13.332
21 10.0 14.616 19.4 7.9 13.882
# o f Diff Co nn Req. Expected # o f Diff Co nn
(fro m Simulatio n) Req.(Calculated)
5.971
12.155
17.790
24.118
29.923
35.977
42.221
47.889
54.062
6.000
12.000
18.000
24.000
30.000
36.000
42.000
48.000
54.000
Numerical Results
# of Simulations per each case = 500
n = 32
10%
20%
30%
40%
50%
60%
70%
80%
90%
<W ADD >
Max Min Avg
3
0 0.104
3
0 0.114
4
0 0.140
2
0 0.074
3
0 0.094
4
0 0.086
3
0 0.084
3
0 0.046
7
0 0.056
Average
<W M1>
Max Min Avg
Max
52 34 42.742 52
52 33 42.988 54
54 35 43.100 52
52 34 43.020 52
53 34 42.896 56
52 34 42.714 52
52 35 42.710 56
53 34 42.834 53
54 34 42.824 53
53 34.1 42.870 53.3
<W M2>
Min Avg
34 42.802
32 42.716
35 42.916
34 42.802
34 42.896
36 42.634
34 42.468
34 42.614
33 42.822
34 42.741
# o f Diff Co nn Req. Expected # o f Diff Co nn
(fro m Simulatio n) Req.(Calculated)
24.904
49.400
74.557
98.931
124.731
148.447
173.743
198.260
223.142
24.800
49.600
74.400
99.200
124.000
148.800
173.600
198.400
223.200
Numerical Results
DiffFactor = 2(|E(G1)-E(G2)|+|E(G2)-E(G1)|)/n(n-1)
500 Simulations for Each Case
0.160
Avg (n=8)
Avg (n=16)
# of Additional Wavelengths
0.140
0.140
Avg (n=32)
0.122
0.120
0.114
0.100
0.104
0.100
0.094
0.080
0.092
0.086 0.084
0.074 0.076
0.068
0.064
0.060
0.062
0.064 0.066
0.056
0.046
0.046
0.040
0.034
0.020
0.020
0.008 0.008
0.012
0.008 0.008
0.000
10%
20%
30%
40%
50%
60%
Difference Factor
70%
80%
90%
Concluding Remarks
 Sometimes, there is no way to have a Survivable
Logical Topology Embedding
on a Physical Topology.
 However, the results say that we can always find
a way to have a survivable embedding by
carefully designing a WDM topology or an IP
topology.
 Moreover, by using a small number of additional
lightpath, we can always preserve survivability
while the reconfiguration is being proceeded.
Thank you