routing and wavelength assignment in wavelength-convertible waveband-switched networks
DESCRIPTION
Routing and Wavelength Assignment in Wavelength-Convertible Waveband-Switched Networks. Routing and Wavelength Assignment in Wavelength-Convertible Waveband-Switched Networks. Fang-Sheng Lin* Ching-Fang Hsu Te-Lung Liu. Outline. Introduction Related Work Reconfigurable MG-OXC architecture - PowerPoint PPT PresentationTRANSCRIPT
Routing and Wavelength Assignment in Wavelength-
Convertible Waveband-Switched Networks
Routing and Wavelength Assignment in Wavelength-
Convertible Waveband-Switched Networks
Fang-Sheng Lin*
Ching-Fang Hsu
Te-Lung Liu
2
Outline• Introduction• Related Work
– Reconfigurable MG-OXC architecture– Waveband Assignment with Path-Graph
(WAPG) algorithm• The Proposed Scheme
– Problem Definition– Least-Configuration with Bounded Conversion
(LCBC) algorithm• Performance Evaluation• Conclusions
3
Introduction (1/5)
• Owning to the development of DWDM systems, the number of wavelengths gets larger and larger.
• Traditional OXCs which switch traffic only at wavelength granularity will need a great deal of wavelength ports.– higher complexity – difficulty associated with controlling and
management of such large OXCs
4
Introduction (2/5)
• The main idea of Waveband Switching (WBS) is to aggregate a set of wavelengths into a band and switch the band using a single port whenever possible.
5
Introduction (3/5)
• The wavelength continuity constraint on lightpath establishment existing in wavelength routed networks also apply to WBS networks.
• One possible way to relax the wavelength continuity constraint is to use wavelength converters at the switching node.
6
Introduction (4/5)
• It is more practical and cost-effective to share a set of limited range wavelength converters at each node.
7
Introduction (5/5)
• Focused on sub-path grouping strategy, we proposed a new heuristic algorithm to solve the dynamic RWA problem of wavelength-convertible WBS networks efficiently.
8
Related Work (1/4)- Reconfigurable MG-OXC
• The Multi-granular Optical Cross-Connect (MG-OXC) architecture with wavelength conversion bank [1]
FXC
BXC
WXC
…
…
…
…
…
……
…
…
…
…
…
… …
X
βY
αX
BTF
BTW WTB
FTB
WXCLayer
FXCLayer
BXCLayer
Y
Wavelength Conversion Bank
9
Related Work (2/4)- Reconfigurable MG-OXC
• There is a unique issue related to using wavelength converters:– In WBS networks, an instantiation of
wavelength conversion requires all wavelengths in a waveband to be de-multiplexed and results in extra ports consumption.
• Hence, inefficient banding and employment of wavelength converters may cause more blocking of future requests due to the limitation of the OXC ports.
10
Related Work (3/4)- WAPG algorithm
• The authors in [1] proposed a heuristic algorithm called Waveband Assignment with Path-Graph (WAPG) to address the effect on the blocking performance and efficient usage of wavelength converters in WBS networks.
11
Related Work (4/4)- WAPG algorithm
• WAPG– Find out a wavelength-continuous path
similar First-Fit algorithm first.– If no wavelength-continuous path can
be found, find a non-wavelength-continuous path using minimum number of converters.
• However, it may cause undesired port usage.
12
The Proposed Scheme (1/5)- Problem definition
• The network topology– G=(V, E)
• Each fiber link has W wavelengths, which are partitioned into B uniform wavebands.
• According to the index continuity, a fixed number K of wavelengths are chosen to be grouped into a band
13
The Proposed Scheme (2/5)- Problem definition
• For the wavelength-convertible WBS networks, the major objectives of dynamic RWA problem include– to minimize the configuration (switching) cost,
i.e., the total number of ports used,– to utilize wavelength conversion in a most
efficient manner, and– to achieve a magnificent network performance
at the same time.
14
The Proposed Scheme (3/5)- Least-Configuration with Bounded Conversion
• We proposed a new heuristic algorithm, called Least-Configuration with Bounded Conversion (LCBC), based on– the fixed routing algorithm,– the layered graph approach, and– a well-designed cost function
15
The Proposed Scheme (4/5)- Least-Configuration with Bounded Conversion
s d
0v 1v 2v 3v
Layer 0
Layer 1
Layer 2
Layer W-1
….
10
Wv 11
Wv 13
Wv12
Wv
00v
01v
03v
02v
10v
11v
13v
12v
20v
21v
23v
22v
An illustration of layered graph modeling
's 'd
transmission edge
conversion edge
16
• The proposed cost function
The Proposed Scheme (5/5)- Least-Configuration with Bounded Conversion
W
DWD vv 1,,,, ',',
0, no wavelength conversion performed
1, wavelength conversion occurredψ=
The extra port consumption at node v while λ is the input channel and λ' is the output channel [9]
Wavelength
conversion degree
Link capacity
The weight factor
17
Performance Evaluation (1/4)
• USAnet – 46 nodes and 76 links.
• Every node is assumed to be a MG-OXC. • Adopting the share-per-node architecture
– 25 wavelengths converters per node
18
Performance Evaluation (2/4)
• Traffic pattern– A Poisson process with mean γ– Exponentially distributed connection
duration time whose mean is 1 time unit – All existing connections can not be
rearranged.
19
Performance Evaluation (3/4)
β vs. blocking probability (W=80, K=10)
93.8%
3.8%
20
Performance Evaluation (4/4)
Blocking probability vs. arrival rate(W=80, K=10, β=0.75)
51.1%
26%
97.8%
21
Conclusions (1/2)• In this paper, we proposed a heuristic algorithm,
named LCBC, to solve the problem of dynamic RWA in wavelength-convertible WBS networks.
• Adopting fixed routing as the routing selection algorithm, we transform the wavelength selection problem into an equivalent shortest-path problem in an auxiliary graph.
• Moreover, we proposed a cost function to calculate an appropriate weight to each edge, such that limited resource, including BTW/WTB ports and wavelength converters, could be utilized more efficiently.
22
Conclusions (2/2)
• To investigate the efficiency, we developed the simulation to observe the performance of LCBC and that of WAPG with various β, and conversion degree.
• LCBC can achieve much significant blocking performance gain.
23