Network Optimization and its Applications in Optical Network Design

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??? ???? ?????? ??????Network Optimization and
its Applications in Optical Network Design

• Supervised by
• Prof. Dr. Abd ElKarim Omar Hassan
• Dr. Khaled Fouad Elsayed
• Faculty of Engineering, Cairo University
• Submitted By
• Zein ElAbedin Mohamed Wali

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Motivation

• Growth wide application of optical
  communication networks
• More users
• More bandwidth requirement (audio, video, .)
• New generation networks combining data / audio/
  video/ HD-TV, Video mail, etc)
• Optical network design is still an active
  research area
• Possibility of application to other OR problems

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Agenda

• Optical fiber networks
• Multiplexing techniques
• WRONs
• Lightpath
• Routing and Wavelength Assignment
• Approaches for RWA
• Proposed approach
• Future work

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Optical fiber networks

• Mainly based on 2 factors
• Optical fiber advantages
• Multiplexing techniques

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Optical fiber advantages

• Huge bandwidth (nearly 50 Tbps)
• Low signal attenuation  (as low as 0.2 dB/km)
• Low power requirement
• Small space requirement
• Low cost
• Flexibility

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Multiplexing techniques

• Space-division multiplexing (SDM)
• Frequency/Wavelength-division multiplexing
  (FDM/WDM)
• several independent logical channels each carried
  on different wavelength

Fiber
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LigthPath

• A lightpath is the basic mechanism of
  communication in WRON.
• lightpath (also referred to as ?-channel),
  bypasses electronic processing at intermediate
  nodes.
• Realized by finding
• physical path
• allocating a free wavelength on each link of that
  path

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Routing and Wavelength Assignment (RWA)

• Problem statement
• Given
• A network topology
• Set of connection requests to be established.
• Required
• To determine lightpath for each connection
• Physical route
• Assigned wavelength

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Routing and Wavelength Assignment (RWA) (Ctd)

• Constraints
• Wavelength continuity constraint
• A lightpath must use the same wavelength on all
  the links along its path from source to
  destination
• Distinct wavelength (capacity) constraint
• All lightpaths using the same link (fiber) must
  be allocated distinct wavelengths.

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Routing and Wavelength Assignment (RWA) (Ctd)

• Illustration (wavelength continuity)

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Routing and Wavelength Assignment (RWA) (Ctd)

• Illustration (distinct wavelength constraint)

D
E
C
B
A
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Routing and Wavelength Assignment (RWA) (Ctd)

• Example WRON

?1 ?2
Optical Cross-Connect
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Routing and Wavelength Assignment (RWA) (Ctd)

• Traffic Type
• Static / Incremental / Dynamic
• Objective
• Min-RWA / Max-RWA
• Fiber Multiplicity
• Single / Multiple
• Request Multiplicity
• Single / Multiple

• Traffic Type
• Static / Incremental / Dynamic
• Objective
• Min-RWA / Max-RWA
• Fiber Multiplicity
• Single / Multiple
• Request Multiplicity
• Single / Multiple

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Agenda

• Network Optimization
• Optical fiber networks
• Approaches for RWA
• Link-based
• Path-based
• Heuristic
• Proposed approach
• Future work

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Approaches for RWA

• Link-based (ILP)
• variables reflect link-flows
• Huge number of variables but considering the
  whole search space
• Explicit wavelength continuity constraint
• Path-based (ILP)
• ILP formulation variables reflect path-flows
• Lower number of variables with reduced search
  space
• Implicit wavelength continuity constraint
• Heuristics
• Greedy, Tabu search

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Agenda

• Network Optimization
• Optical fiber
• Approaches for RWA
• Proposed approach
• Related work
• Candidate path calculation
• Addressing Multiple fiber
• Min-RWA objective
• Network growing problem
• Practical examples
• Future work

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Proposed approach

• Path-based approach
• Related Work
• Ozdaglar et. al.(2003) Min-RWA, unique requests,
  single fiber.
• Lee et. al.(2004) Min-RWA, multiple requests,
  multi-fiber. multi-fiber incorporated into the
  ILP, Based on lagrangean heuristic.
• Saad et. al.(2004) Max-RWA, multiple requests,
  multi-fiber. multi-fiber incorporated into the
  ILP, Based on Maximum coverage heuristic.

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Proposed approach

• Based on the work of Ramaswami et. al. 1995
• Candidate path calculation for each SD pair
• Link-disjoint paths
• Link-distinct paths
• We adopted the link-disjoint paths criterion
• Avoid congested links (load balancing).
• No. of link-disjoint paths is less than
  link-distinct path
• Contributes to lower the number of Branch and
  Bound iterations.

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Addressing multi-fibers

• Network is modeled to an undirected multi-graph
  instead of a simple undirected graph

1
0
2
2
2
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ILP Model

• Given
• m traffic demand vector
• Calculate
• A, PxSD incidence matrix
• B, PxM incidence matrix
• Required
• C, PxW incidence matrix

P(sd1)
SD1
P(sd2)
SD2
Amatrix
B matrix
P(sdR)
SDR
Connection requests
Candidate paths
Links
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ILP Model (Ctd)

• Min-RWA objective
• Assign increasing weights to increasing index of
  used wavelengths

Objective Minimize Capacity
constraint Traffic demand Constraint Integrali
ty constraint
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Network Growing problem

• Current network topology and resources can not
  satisfy the demanded requests
• Required
• to obtain the minimum set of modifications to
  satisfy the connection requests.
• Our assumption the suggested modifications are
  only the addition of fibers to already existing
  links.

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Network Growing problem (Ctd)
Start
A
LP solve library
Calculate Candidate Paths
Solve the model
Yes
No
Feasible?
Calculate A, B matrices and Build the LP model
Build new model with Max . of wavelengths
No solution
Solve the model
Report solution
A
Calculate modifications
Network growing
End
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Agenda

• Network Optimization
• Optical fiber
• Approaches for RWA
• Proposed approach
• Practical examples
• Performance metrics
• Performance evaluation
• Network models
• Results
• Future work

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Performance metrics

• Objective value (Min. no. of wavelengths, W)
• Elapsed time (T in mSec)
• Total no. of iterations
• Branch Bound iterations (BB)

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Performance Evaluation

• Model test results
• Variable no. of SD pairs
• Variable no. of requests (increasing multiplicity
  for the same SD pairs)
• Variable no. of candidate paths (search space)
• Comparison with Greedy EDP

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Network models

• Cost239 Network (11 nodes, 23246 links)

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Network models (Ctd)

• NSFNET Network (14 nodes, 21242 links)

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Results

• Increasing SD pairs
• NSFNET network, increasing SD pairs

Increasing no. of iterations with increasing SD
pairs
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Results (Ctd)

• Increasing requests for the same 10 SD pairs
  (through multiplicity)
• NSFNET network, increasing requests

Increasing no. of iterations is less grave with
multiplicity
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Results (Ctd)

• Increasing candidate paths
• Cost239 network, 80 requests, varying candidate
  paths

Minimizing the no. of candidate paths can lead to
false optimum
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Results (Ctd)

• Comparison
• Comparison between proposed and Greedy-EDP
  approaches

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Agenda

• Network Optimization
• Optical fiber networks
• Approaches for RWA
• Proposed approach
• Future work

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Future work

• Network optimization
• Place and route problem in VLSI
• Assignment problems (scheduling, crew assignment,
  job assignment )
• Optical fiber network problems
• Multicasting
• Dynamic traffic
• Wavelength conversion

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Thank You!
Even if the researcher does not find what was
initially expected, the pursuit of a personally
important topic is still rewarding and generally
produces continuing researches.
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References

• B. Mukherjee, "Optical communication networks",
  McGraw-Hill Publishers, 1997.
• I.Chlamtac, A.Ganz, and G.Karmi, Lightpath
  Communications An Approach to High Bandwidth
  Optical WANs IEEE Transactions on
  Communications, vol.40, no.7, July1992.
• H. Zang, J. P. Jue, and B. Mukherjee, A Review
  of Routing and Wavelength Assignment Approaches
  for Wavelength-Routed Optical WDM Networks,
  SPIE/Baltzer Optical Networks Magazine (ONM),
  vol. 1, no. 1, January 2000.
• J. S. Choi, N. Golmie, F. Lapeyrere, F. Mouveaux,
  and D. Su, A Functional Classification of
  Routing and Wavelength Assignment Schemes in DWDM
  Networks Static Case, Journal of Optical
  Communication and Networks, January 2000.

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References

• D. Banerjee, and B. Mukherjee, A Practical
  Approach for Routing and Wavelength Assignment in
  Large Wavelength-Routed Optical Networks," IEEE
  Journal on Selected Areas in Communications, Vol.
  14 No. 5, 1996.
• R.M. Krishnaswamy, and K.N. Sivarajan,
  Algorithms for Routing and Wavelength Assignment
  Based on Solutions of the LP-Relaxation, IEEE
  Communications Letters, vol. 5, no. 10, October
  2001.
• A. E. Ozdaglar, and D. P. Bertsekas, Routing and
  Wavelength Assignment in Optical Networks,
  IEEE/ACM Transactions on Networking, vol. 11, no.
  2, April 2003.
• M. Saad, and Z-Q. Luo, "On the Routing and
  Wavelength Assignment in Multifiber WDM
  Networks", IEEE Journal on Selected Areas in
  Communications (special series on optical
  communications and networking), vol. 22, no. 9,
  November 2004.

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References

• R. Ramaswami and K. Sivarajan, Routing and
  Wavelength Assignment in All-Optical Networks,
  IEEE/ACM Trans. Networking, vol. 3, October 1995.
• P. Manohar, D. Manjunath, and R. K. Shevgaonkar,
  Routing and Wavelength Assignment in Optical
  Networks from Edge Disjoint Path Algorithms,
  IEEE communication letters, Vol. 6, No. 5, May
  2002.
• C. Dzongang, P. Galinier, and S. Pierre, "A Tabu
  Search Heuristic for the Routing and Wavelength
  Assignment Problem in Optical Networks", IEEE
  Communications letters, Vol. 9, No. 5, May 2005.
• R.K. Ahuja, T.L. Magnanti and J.B. Orlin,
  "Handbooks in Operations Research and Management
  Science", Network Flows chapter, Elsvier science
  publisher B.V., 1989.
• X. Jia, D. Du, X. Hu, H. Huang, and D. Li,
  Placement of Wavelength Converters for Minimal
  Wavelength Usage in WDM Networks, IEEE
  INFOCOM'02, New York, June 2002.