BALANCED RESOURCE SHARE MECHANISM
IN OPTICAL NETWORKS
Hyeon Park, Byung-Ho Yae
ETRI, Daejeon, South Korea,
Dong-Hun Lee, Sang-Ha Kim
Chungnam National University, Daejeon, South Korea
Keywords: Resources Share, SRLG, Optical Networks.
Abstract: Existing protection mechanisms to rapidly recover the failures allocate the backup path just SRLG-
disjointed with working path. However, these mechanisms have the low resource utilization because the
resource is not shared among the backup paths. To complement it, Kini (Kini et al., 2002), Somdip (Somdip
et al., 2001) and so on, have proposed the mechanisms to share the resources of the backup paths. Although
these mechanisms can improve the efficiency of bandwidth usage, those did not consider the unbalanced
resource share of backup paths. The backup paths can be centralized on the specific link so that the idle
resource is not used. As a result, as those do not use the resource efficiently the whole resource utilization is
not good. So we propose the mechanism to enhance the resources utilization as settling down the
unbalanced resource share to recover simultaneous failures. We formulate the problem to minimize the
number of the used backup resource (exactly, wavelengths) as considering the maximum link load. We
compare the existing mechanisms with our mechanism by the spare resource capacity as the result of the
simulation.
1 INTRODUCTION
Because the granularity of the optical connection is
coarser than that of the existing network, a single
fiber cut can potentially influence a total of 1.6 Tb/s
of traffic in optical networks. So, the fiber cut results
in the significant loss of traffic and thus the
survivability in optical networks is important.
The mechanism proposed by Kini can save
bandwidth by ensuring the sharing of the backup
path among all working paths with the same source
and destination node. And Somdip’s mechanism can
improve the efficiency of bandwidth usage by
pooling backup path capacity. However, the
resource of these mechanisms can be centralized on
the specific link so that the idle resource is not used.
So we propose the mechanism to enhance the
resources utilization as settling down the unbalanced
resource share. We formulate the problem to
minimize the number of the used backup resource
(exactly, wavelengths) as considering the maximum
link load.
In our mechanism, two-level SRLG for the
backup path selection is used: the first level, Low-
SRLG is for SRLG-disjoint path with its working
path, that is, for the backup path sharing decision
and the second level, High-SRLG is for the same
effect such as the threshold hop limit using the sub-
domain information of the working path. Besides,
this High-SRLG can be the information to eliminate
the link accommodated the unbalanced sharing
backup paths. For the balanced resource sharing
through two-level SRLG the backup paths are
allocated the same as the sub-domain of the working
path as much as possible.
We give the problem definition and Integer Linear
Programming ILP formulations. The ILP
formulation has much more time consumption and is
difficult to solve with increasing problem size. So,
we provide the heuristic algorithm of the proposed
resource shared mechanism and the backup path
selection algorithm and present experimental results.
97
Park H., Yae B., Lee D. and Kim S. (2006).
BALANCED RESOURCE SHARE MECHANISM IN OPTICAL NETWORKS.
In Proceedings of the International Conference on Signal Processing and Multimedia Applications, pages 97-100
DOI: 10.5220/0001571800970100
Copyright
c
SciTePress
2 RELATED WORKS
2.1 Single Link Failure Recovery
Mechanism (SFRM)
In general, most of the protection and restoration
mechanism consider the failure of just the single
component such as a link or a node. It is a typical
approach to provide the survivability.
In Somdip’s mechanism, when a failure occurs in
the SRLG and the restoration protocol for the
corresponding lightpaths’ activation of the
restoration channels RCs on backup path starts to be
processed, the mechanism finds primarily available
RCs in the pool and uses them for the restoration.
2.2 Multiple Link Failures Recovery
Mechanism (MFRM)
In the real world, in general, several failures in an
optical network occur simultaneously. The
mechanisms for the multiple failures consider the
working/back-up paths with the same source and
destination node.
Doucette proposed the design formulation and
procedure for the planning any span-restorable
network for a known set of SRLGs. And it showed
how total capacity depends on the relative number or
frequency of co-incident SRLGs and quantified how
the type of SRLG will impact design costs. That is,
it emphasizes which SRLG is the most deleterious to
network efficiency. However, because SRLG is
configured at the start of the network initialization
the co-incident SRLGs depends on the network plan
including the placement of SRLGs.
3 PURPOSE OF THE PROPOSED
MECHANISM
Fig. 1 describes why the network needs to
accommodate the balanced sharing backup paths.
All backup paths are allocated to disjoint their
working paths. Fig. 1 (a) represents the backup paths
are not shared on the same wavelength between
node 5 and 6. Therefore, the resources are wasted. In
case of Fig.1 (b), although b1 and b2 share the
wavelength it still wastes the resources due to b3. If
1 fiber accommodates 2 wavelengths, Fig. 1 (b)
needs two fibers. However, if the backup paths are
decentralized to the wavelength in use, the above
resource constraint is fulfilled and the Fig. 1 (c)
satisfies this condition.
As a result, our purpose is to minimize the number
of the wavelength used for the backup path in the
network.
W1 W3
W2
W4
b3b1 b2
1
Node 2-Node3
W1:
λ
1
W3 :
λ
2
32
4
7
5
8
6
Node 5-Node6
b1:
λ
1
b2 :
λ
2
b3 :
λ
4
W4 :
λ
4
b4
No d e 7- Node 8
b4:
λ
1
W2 :
λ
2
W1 W3
W2
W4
b3b1 b2
1
Node 2-Node3
W1:
λ
1
W3 :
λ
2
32
4
7
5
8
6
Node 5-Node6
b1:
λ
1
b2 :
λ
2
b3 :
λ
4
W4 :
λ
4
b4
No d e 7- Node 8
b4:
λ
1
W2 :
λ
2
(a) Unshared backup paths
W1 W3
W2
W4
b3b1,b2
1
32
4
7
5
8
6
b4
No de 2- No de 3
W1:
λ
1
W3 :
λ
2
No de 5- Node 6
b1,b2:
λ
1
b3 :
λ
4
W4 :
λ
4
No de 7- Node 8
b4:
λ
1
W2 :
λ
2
W1 W3
W2
W4
b3b1,b2
1
32
4
7
5
8
6
b4
No de 2- No de 3
W1:
λ
1
W3 :
λ
2
No de 5- Node 6
b1,b2:
λ
1
b3 :
λ
4
W4 :
λ
4
No de 7- Node 8
b4:
λ
1
W2 :
λ
2
(b) Shared backup paths without considering
maximum link load
W1 W3
W2
W4
b1,b2
1
32
4
7
5
8
6
b3,b4
Node 2-Node3
W1:
λ
1
W3 :
λ
2
Nod e 5-No de 6
b1,b2:
λ
1
W4 :
λ
4
Nod e 7-No de 8
b3,b4:
λ
1
W2 :
λ
2
W1 W3
W2
W4
b1,b2
1
32
4
7
5
8
6
b3,b4
Node 2-Node3
W1:
λ
1
W3 :
λ
2
Nod e 5-No de 6
b1,b2:
λ
1
W4 :
λ
4
Nod e 7-No de 8
b3,b4:
λ
1
W2 :
λ
2
(c)
Proposed Shared backup paths with considering
maximum link load
Figure 1: The resource (wavelengths) sharing in the
network.
4 PROBLEM DEFINITION AND
BACKUP PATH ALGORITHM
4.1 ILP Formulations
The proposed mechanism includes two level SRLG,
Low-SRLG and High-SRLG. Low-SRLG means a
group of links that are subject to a common risk,
such as a conduit cut. High-SRLG is defined to
select the backup path closed to its working path due
to the hop counts or the link length. In addition to
the link length, High-SRLG is defined to avoid the
unbalanced link load due to the concentrated sharing
in a link. Thus, this High-SRLG is defined into the
geographical region as a domain concentrated with
the network nodes.
We formulate the problem to minimize the used
resource. We consider the SRLG information (two-
level SRLG) to select the backup paths. We give the
ILP formulation to provide optimal solution as
follows: The objective function equation (1)
SIGMAP 2006 - INTERNATIONAL CONFERENCE ON SIGNAL PROCESSING AND MULTIMEDIA
APPLICATIONS
98
minimizes the sum of the number of wavelengths
(w) used for backup paths (B) on the link i, j
between source s and destination d.
∑∑∑
:
sd
ijw
sd ij w
Objective
MIN B
(1)
For the objective function the constraints are as
follows:
(2) The number of backup paths is the same as the
number of working paths in the network. (It
means that there are the source and terminal
node over its paths in the network whether the
distance of the paths is long or short.)
(3) The total link capacity (the number of
wavelengths) in link i,j is greater than the total
number of wavelengths used for backup paths in
link i,j.
(4) The backup path is conserved at each link along
the path (In case of the working path, this
constraint is not necessary).
(5) The spare capacity in the link i,j is that one
subtracted the working path capacity (the
number of wavelengths used for the working
paths) from the total capacity in the link i,j.
Subjects to:
β
⋅= = =
=≠≠ =
∑∑ ∑∑
,,
,, ,
,,(,),
(,),
sd w sd
ijw uvw b b b
sd ij w W uv w
pp p p
B P P P iji sit js
uv u s u t v s v t
(2)
≤∀=
∑∑
max max
., (,),
sd sd
ijw ij ijw
sd w ijw
BLC ijL IntB
(3)
ββ
⋅− =
∑∑
(, ) ( ,)
0, , , ,
sd w sd w
ijw jiw b b
jij w i ji w
BB sdisit
(4)
sd
ββ
ββ
⋅− = =
⋅− = =
≤=
∑∑
∑∑
∑∑ ∑∑
(, ) ( ,)
(, ) ( ,)
1, , , ,
1, , , ,
,,(,)
sd w sd w
ijw jiw b b
jijw ijiw
sd w sd w
j
iw jiw b b
jijw ijiw
sd sd
ijw ij ij ij ijw
sd w w
BBsdisit
BB sdisit
BS SC P ij
(5)
In addition to single failure, the constraint for dual
failures is considered as shown in Fig. 2. The link cd
on the backup path p1 is simultaneously failed when
the link ij on the backup path B1 of the working path
w1, B2, and B3 is failed. For the previous objective
function, the constraint of the dual failures is as
follow:
Γ≤
∑∑
i ,(,),(,)
sd ab
ijw ijw ij
sd w
BSijab
(6)
(6) There is enough spare capacity to recover the
dual failures (two links or two paths at once. (If
the required capacity (at the left side) is greater than
the spare capacity, it is infeasible. For example, if 3
backup paths share the wavelength w, to recover the
failure of the link (i,j) 3 wavelengths are needed in
link (a,b)).
≤≤
constant
: The total number of wavelengths oneach link and 1 .
: The total link capacityunits(totalwavelengths)on thelink ( , ).
: The working path with wavelength w on the link( , ).
,:T
:
ij
sd
uvw
pp
Notation
wwW
Ci
u
s
s
j
pv
t
β
he starting or terminal nodeof the working path p.
variable
: 1, if the backup path for a working path( , )uses
wavelength in link(i,j), 0, otherwise.
: The inverse of the number of the backup paths
w
sd
ijw
Bsd
w
λβ
≤≤
Γ
3)
1
sharing
the wavelength w, (1 )
(If 3 backup paths share wavelength ,then is 1/
: Spare capacity(the number of wavelengths)on thelink ( , ).
:The number of backup paths sah
w
ij
ab
ijw
wW
Sij
ring the wavelength w link (i,j)
The number of wavelength needed to recover the backup paths
in link (a,b)
, : The starting or terminal nodeof the backup path b.
bb
st
P1
B1
i
j
c
d
a
b
B2
B3
P1
B1
i
j
c
d
a
b
B2
B3
Figure 2: Simultaneous link failures in the network.
4.2 Algorithm for Backup Paths
The working path and the backup path are basically
selected based on Low-SRLG mechanism like
Somdip’s mechanism. In addition to Low-SRLG, the
High-SRLG (Fig. 3) is added in the proposed
mechanism. The backup paths is selected the same
as the sub-domain of the working path as much as
possible.
Figure 3: Backup path selection algorithm : Low-SRLG
and High-SR LG based.
cur_connection : current connections
WP_list : the link list of the selected working paths
accept_region = find_region() //find the whole sub-domains
on the working path //find the rest sub-domains
not_accept_link_list =
find_not_accept_region (accept_region)
// disable the links on the rest of the working paths
set_link_disable(not_accept_link_list)
result = find_Low_backup()//applies the Low-SRLG
algorithm
if result == fail
then set_link_enable(not_accept_link_list) //discharges the
sub-domains
find_Low_backup()
end if
set_link_enable(){
for bk_link // for all backup links
if (backup Path == share)//check the backup path with the
others
then increase band-width of backup links
else not increase band-width of backup links
increase simultaneous two failures count
end for }
BALANCED RESOURCE SHARE MECHANISM IN OPTICAL NETWORKS
99
5 SIMULATION RESULTS
We assumed that the working path of the proposed
mechanism is selected by the shortest. The test
network model is consisted of 7 sub-domains, 39
nodes and 69 links. The nodes from the node
number 1 to 18 are used as a source node and the
nodes from the node number 19 to 39 are used as a
destination node.
For the comparison, we simulated the algorithm for
the Somdip’s mechanism represent by Low-SRLG
algorithm, without considering unbalanced link load.
And High-SRLG algorithm means the proposed
mechanism with considering unbalanced link load
by High-SRLG identification. We setup 50
connections, 1connection a unit time. And it is
repeated 50 through 100 times. We suppose the
shortest working and backup paths. We considered
the following cases.
Static path selection: predefined working paths and
backup paths for the simultaneous two failures : Fig. 4
: The resource usage of working/backup paths
by Low-SRLG algorithm/by High-SRLG algorithm
Dynamic (Random) path selection: dynamically select
working paths and backup paths for the simultaneous two
failures : Fig. 5
: The resource usage of working/backup paths
by Low-SRLG algorithm/by High-SRLG algorithm
As shown Fig. 4, the High-SRLG algorithm
compared with the Low-SRLG can distribute more
resource in case of the dynamic connection. That is,
the number of non shared backup paths in case of
High-SRLG is 216 and Low-SRLG is 184. In Fig. 5,
the high-SRLG algorithm also can distribute more
resource in case of static connection
.
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# of Label
a1
a3
a5
a7
b2
b4
b6
c1
c3
c5
c7
d1
d3
d5
d7
d9
e1
e3
e5
f2
f4
f6
f8
g2
g4
g6
g8
h1
h3
h5
h7
Link ID
Hi g hSRL G
LowSRLG
Figure 4: The resource usage of working paths/backup
paths: Low-SRLG/High-SRLG algorithm under Random
Connections.
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a1
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f4
f6
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g2
g4
g6
g8
h1
h3
h5
h7
Link ID
HighSRLG
LowSRLG
Figure 5: The resource usage of working paths/backup
paths: Low-SRLG/High-SRLG algorithm under Static
Connections.
6 CONCLUSIONS
In this paper, we proposed the shared resource path
provisioning mechanism to guarantee the
survivability. We presented the capacity design
method and the optimization model to improve the
link utilization and simulated to measure the
resource utilization of the proposed mechanism.
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Y. Ye et al., 2001. A Simple Dynamic Integrated
Provisioning/Protection Scheme in IP over WDM
Networks, IEEE Commun. Mag., Nov. 2001, pp. 174-
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J. Doucette et al., 2002, Capacity design studies of span-
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APPLICATIONS
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