Post on 28-Dec-2015
Survivable Logical Topology Design in WDM Optical Ring
Networks
Hwajung Lee, Hongsik Choi,
Suresh Subramaniam, and Hyeong-Ah Choi*
The George Washington University
Supported in part by
DARPA under grant #N66001-00-18949
(Co-funded by NSA)
DISA under NSA-LUCITE Contract
NSF under grant ANI-9973098
Outline
Introduction – Network SurvivabilityMotivationProblem Formulation Problem ComplexityHeuristic AlgorithmNumerical ResultsConcluding Remarks
Network Survivability
To guarantee for users to use the network service without any interruption.
Each layers have their own fault recovery functions.
Fault propagation
ATM
ATM
IP
IP
IP IP
WDM Optical Network
Physical Fiber Plant
SONET/SDH
SONET/SDH
Introduction
Logical topology (Upper Layer) is called survivable if it remains connected in the presence of a single optical link failure.
Faulty Model : Single optical link failure.
Survivable Logical TopologyMotivations
Survivable Logical Topology
Survivable
Electronic layer is connected even when a single optical link fails
Map each connection requestto an optical lightpath.
1
3
52
4
0
1
2
34
5
0
1
2
34
5
0
Motivations
Upper Layer= Logical Topology
Optical Layer= Physical Topo.
Not Survivable
Desirable!
Sometimes, there is no way to have a Survivable
Logical Topology Embedding
on a Physical Topology.
Survivable Logical Topology
e1
e2
…
…a
c
b
d …
…
…
…
d
b
c
a
Motivations
Electronic Layer= Logical Topology
Optical Layer= Physical Topo.
2-Edge Connected
Survivable Logical Topology Design Problem(SLTDP)
Given a physical topology, and a logical topology = a set of connection requests.
Objectives Find a route of lightpath for each connection
request, such that the logical topology remains connected after a single link failure if possible.
Otherwise, determine and embed the minimum number of additional lightpaths to make the logical topology survivable.
Problem Formulation
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
Survivable LT design possible when min.degree >= No survivable LT design for min. degree <= ( -1)
2n 3 n
2
Problem Complexity
k
a 2
b 1
f
e h
b 2
i
a 1
d 1
c 1
g
c 2
l
jd 2
C 1
C 2
C 3C 4
a 1
f
b 2
a 2
e
b 1
k
3-edge Connected Graph: not Survivable
Problem Complexity
b1
b3
b2
b4
c1
c3
c2
c4
d1
d3
d2
d4
e1
e3
e2
e4
a1
a3
a2
a4
C1
C2
C3
C4
a1
a4
a2
a3
e2
e1
e4
e3
c4
c2
c3
c1
b4
b3b2
b1
d3
d1
d4
d2
4-edge Connected Graph: not Survivable
Problem Complexity
n-10
n/4+1
n/3-1
n/4
n/2n/2-1 2n/3
n/2+j
L R
Number of Nodes = b Number of Nodes = b
j n-j-1...
... ...
.... . .
...
...
...
si +i (L); si - I + n -1(R)
t: highest index in L smallest_component4 cases: t -1; t ; t -2; t= -1
n 6
n 6
n 4
n 3
n 4
n 3
n 3
Shortest Path Routing: Survivable if (minimum d ) 2n
3
Problem Complexity
: Vodd
: Veven
Kn/2-1 Graphn-1Kn/2-1 Graph 0
0 n-1
... .........
...
Shortest Path Routing: not Survivable if (minimum d -1 )
n 2
Problem Complexity
Heuristic Algorithm Heuristic Algorithm
based on Shortest Path Routing
Assign logical links to lightpaths.Cut each optical link
and Calculate the # of Components.Find an optical link (x,y) with the maximum #
of components.Add an additional lightpath without using (x,y).Repeat the above procedure
until the logical topology being survivable.
Numerical Results# of Simulations = 1000
n = 100
0
5
10
15
20
25
0.02
80.
040.
060.
08 0.1
0.2
link probability p
aver
age
# o
f ad
dit
ion
al l
igh
tpat
hs
2 edge-connected
arbitrary
22.953
7.037
1.8611.938
0.0080.0023.357
Numerical Results
Numerical Results# of Simulations = 1000
n = 200
0123456789
10
0.02
80.
040.
060.
08 0.1
0.2
link probability p
aver
age
# o
f ad
dtio
nal
lig
htp
ath
s
2 edge-connected
arbitrary
8.889
0.4940.549 0.023
0.027
4.632
Numerical Results
Numerical Results# of Simulations = 1000
n = 300
-1
1
3
5
7
9
11
0.02
80.
050.
070.
090.
110.
130.
15
link probability p
aver
age
# o
f ad
dti
on
al l
igh
tpat
hs
2 edge-connected
arbitrary
10.293
0.533
5.585
0.814
0.0270.027
Numerical Results
Concluding RemarksSurvivable LT design in WDM ring networkDetermine if survivable design possible from G
Degree constraint : -1, Edge-connectivity constraint
Heuristic algorithm: almost optimal Further Research
Tighter bounds WDM mesh topology Reconfiguration of Survivable Logical Topology
2n 3
n 2
Concluding Remarks