An Efficient Strategy for Wavelength Conversion in WDM p-Cycle Networks Dominic A. Schupke, Matthias C. Scheffel Wayne D. Grover Fourth International Workshop on the Design of Reliable Communication Networks (DRCN 2003) Munich University of Technology Institute of Communication Networks TRLabs & University of Alberta 21 October 2003

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN p-Cycle Concept Description Network protection strategy –Spans –(Transit nodes, paths) p-Cycles –Preconfigured closed paths –Reserved capacity –In mesh network B E C A D p-Cycle Node Span

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN p-Cycle Concept Span Protection Mechanism –On-cycle span Span is used by p-cycle B E C A D p-Cycle Protection path Node Span  1 protection path

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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 B E C A D  2 protection paths  1 protection path p-Cycle Protection path Node Span

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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 B E C A D p-Cycle Working path Wavelength links Full conversion netVWP Approach

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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 B E C A D p-Cycle Working path Wavelength links No conversion netWP Approach

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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 p-Cycles in WDM Networks B E C A D Partial conversion

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN p-Cycles in WDM Networks A E D C B Working paths without conversion Working WP p-Cycles without conversion p-Cycle WP Converters for p-cycle access Partial Wavelength Conversion at Nodes wWP_pWP_accessIfRequired & wWP_pWP_accessFull Approach If Required Full

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN A E D C B p-Cycles in WDM Networks p-Cycles with full conversion p-Cycle VWP Working paths without conversion Working WP Partial Wavelength Conversion at Nodes (+ straddling span converters) wWP_pVWP Approach

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN COST239 Network Pan-European optical core network 11 nodes, 26 spans Average nodal degree = counterdirectional fiber pair per span 32 wavelengths per fiber Given demands –Dense matrix –1 to 11 lightpaths per node (average = 3.2) –Symmetry modification Case Study Scenario Copenhagen London Amsterdam Berlin Paris Brussels Luxembourg Prague Vienna Zurich Milan

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN Results Total Cost Comparison fullyEquipped = converters for any available wavelength partiallyEquipped = converters for used wavelengths only

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN Results Capacity-Efficiency Evaluation Capacity-efficiency = protection capacity working capacity

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN Results Wavelength Converter Allocation

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN 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

Technische Universität München Institute of Communication Networks Prof. Dr.-Ing J. Eberspächer Matthias C. Scheffel DRCN Comparison of p-Cycle Configurations netVWP wWP_ pWP_ accessIf Required wWP_ pWP_ access Full wWP_ pVWP netWP Protection efficiency highesthighvery highhighvery low Convertersmostvery fewfewmoreno Tunable lasers required noyes n/a Termination of protection paths yessomeyes no Wavelength flexibility highestlowhighhighern/a