An Efficient Strategy for Wavelength Conversion in WDM p -Cycle Networks

1. Fourth International Workshop on the Design of Reliable Communication Networks (DRCN 2003) An Efficient Strategy for Wavelength Conversionin WDM p-Cycle Networks 21 October 2003 Dominic A. Schupke, Matthias C. Scheffel {schupke,scheffel}@lkn.ei.tum.de Wayne D. Grover {grover@trlabs.ca} Munich University of Technology Institute of Communication Networks TRLabs & University of Alberta

2. Motivation • WDM transport networks are becoming more “optical” • Functions realized in optical domain (e.g. switching) • Routing and wavelength assignment (RWA) problem • High wavelength converter cost  Partial wavelength conversion • Need for reliability against network failures • Low capacity redundancy • Fast protection p-Cycle concept

3. Outline • p-Cycle Concept • p-Cycles in WDM Networks • Full wavelength conversion • No wavelength conversion • Partial wavelength conversion • Implementation • Case Study Scenario • Results • Conclusions / Outlook

4. p-Cycle Concept Description • Network protection strategy • Spans • (Transit nodes, paths) • p-Cycles • Preconfigured closed paths • Reserved capacity • In mesh network B E Node Span C p-Cycle D A

5. p-Cycle Concept Span Protection Mechanism • On-cycle span • Span is used by p-cycle 1 protection path B E Node Span C p-Cycle D Protection path A

6. p-Cycle Concept Span Protection Mechanism • On-cycle span • Span is used by p-cycle • Straddling span • Span’s end nodes lie on p-cycle • Span is not used by p-cycle 1 protection path 2 protection paths B E Node Span C p-Cycle D Protection path A

7. p-Cycles in WDM Networks Full Wavelength Conversion at Nodes • Different wavelengths along a path • Termination of paths at each node  Virtual Wavelength Path VWP • p-Cycle can protect working links at any wavelength +Capacity-efficient protection – High converter cost netVWP Approach B E C D A Full conversion p-Cycle Working path Wavelength links

8. p-Cycles in WDM Networks No Wavelength Conversion at Nodes • Same wavelength along a path • No termination along paths  Wavelength Path WP p-Cycle can protect working links at same wavelength only +No converter cost – More capacity redundancy netWP Approach B E C D A No conversion p-Cycle Working path Wavelength links

9. p-Cycles in WDM Networks Partial Wavelength Conversion at Nodes • Converter Pool with tunable lasers • Wavelength conversion for some paths • Termination of some paths • Idea: Make p-cycles accessible for working links at different wavelengths by providing a small number of converters B E C D A Partial conversion

10. p-Cycles in WDM Networks Partial Wavelength Conversion at Nodes wWP_pWP_accessIfRequired & wWP_pWP_accessFull Approach p-Cycles without conversion p-Cycle WP • Converters for p-cycle access • If Required B • Full E C Working paths without conversion Working WP D A

11. p-Cycles in WDM Networks Partial Wavelength Conversion at Nodes wWP_pVWP Approach p-Cycles with full conversion p-Cycle VWP (+ straddling span converters) B E Working paths without conversion Working WP C D A

12. Implementation Mathematical Programming Integer linear program (ILP) • Objective function: Minimize ( ∑ working path lengths + ∑p-cycle lengths + number of converters • converter cost ) • Constraints: (1) Provide WP working paths to satisfy the demands (2) Allocate p-cycles to provide protection for any single span failure (3) Insert converters according to architecture (4) Use one wavelength at most once per fiber Joint optimization of working and protection capacity plus total converter cost

13. Case Study Scenario COST239 Network • Pan-European optical core network • 11 nodes, 26 spans • Average nodal degree = 4.7 • 1 counterdirectional fiber pair per span • 32 wavelengths per fiber • Given demands • Dense matrix • 1 to 11 lightpaths per node (average = 3.2) • Symmetry modification Copenhagen London Berlin Amsterdam Luxembourg Brussels Prague Zurich Paris Vienna Milan

14. Results Total Cost Comparison fullyEquipped = converters for any available wavelength partiallyEquipped = converters for used wavelengths only

15. protection capacity working capacity Capacity-efficiency = Results Capacity-Efficiency Evaluation

16. Results Wavelength Converter Allocation

17. Conclusions / Outlook • Conclusions: p-Cycle configurations in WDM networks with partial wavelength conversion can reduce the total network cost • Capacity-efficient protection • Small amount of redundant capacity • More flexibility towards changing demand patterns • Small number of converters • Outlook: Performance evaluation of online routing and protection

18. Comparison of p-Cycle Configurations