~1~Vishal AnandVishal AnandWavelength Band Switching in Multi-granular Optical WDM NetworksVishalVishalAnandAnandCollaborators X. Collaborators X. CaoCao, Dr. Y. , Dr. Y. XiongXiongand Dr. C. and Dr. C. QiaoQiaoLANDER, CSE Department, SUNY at BuffaloLANDER, CSE Department, SUNY at Buffalo~2~Vishal AnandVishal AnandOutlineλ The Problem with present WDM networksλ Concept of wavelength band switching: 3 layer waveband switching OXC architectureλ Wavelength Band Switching: Schemes and Grouping Strategiesλ Wavelength Band Switching Vs Wavelength Routed Networks: How similar, How differentλ Performance of Wavelength Band Switching: Techniques for Static and Dynamic Traffic: ILP, Algorithms and simulation resultsλ A Single-layer waveband switching OXC architectureλ Wavelength Vs Waveband Conversionλ New techniques for failure recovery in WBS networksλ Conclusions~3~Vishal AnandVishal AnandPresent WDM networks : The Problemλ Internet traffic demand on the riseλ Only way to keep up: WDMλ Causes deployment of more fibers and more wavelengths per fiber (DWDM)λ In-turn implies increased size of Optical Cross-connects (OXC), with large port countsλ Hence, managing/controlling (NMS, EMS) this large amount of traffic, associated resources: critical, difficult, complicated!~4~Vishal AnandVishal AnandPresent WDM networks : The Problem(cont'd) λ This translates to increased cost: both Capital (CAPEX) and Operating (OPEX)λ Despite the technological advances:λ in WDM, Photonic-XC systems, switching fabricλ The deployment and potential use is limitedλ Unproven reliability and costs of huge switches (e.g. 1000x1000 ports) λ Large footprint (size), power requirements and (un) scalability concerns~5~Vishal AnandVishal AnandThe typical Optical Cross-Connect (OXC)λ Switching at an optical node—too many wavelength-ports~6~Vishal AnandVishal AnandWavelength Band Switchingλ Wavelength band: a group of several wavelengthsλ WBS: A new switching hierarchy with multiple granularityλ WBS Networks: Use WBS in conjunction with a multi-granular OXC, MG-OXCABCDλ0Switch band of 4 wavelengths using 1 portTotal Ports = 1 + 1x2 + 1x2 + 1 = 6+add/drop+mux/demux only!λ3b0λ1λ2Typical-OXCMG-OXCSwitch each wavelength individuallyTotal ports = 4 + 4x2 + 4x2 + 4 = 24+add/drop+mux/demux b0ABCDb0b0~7~Vishal AnandVishal AnandA Three-layer MG-OXCλ Any fiber (bands) can be demultiplexed into bands (wavelengths) using FTB/BTWλ Any band (wavelength) can be multiplexed into fibers (bands) using BTF/WTBλ Fibers/bands/wavelengths are switched at the FXC/BXC/WXC-layersλ Port typesλ Cross-connect – bypass trafficλ Add/drop – add/drop trafficλ Mux/Demux – muxed/demuxedtraffic~8~Vishal AnandVishal AnandExample:WBS using a 3-layer MG-OXCλ 2 individual lightpaths: λ0on fiber F1bypassing the node and λ1to be added locallyλ After demux. F1, λ0is extracted and grouped with λ1after going thro muxer(s)λ Finally λ0and λ1are mux. (combined) in a band and go out on fiber F2 “together”λ0λ1~9~Vishal AnandVishal AnandClassification of WBS Schemesλ Use the pre-determined wavelength set scheme as it is the simplestλ Each fiber has a fixed # of bands (B), each band has a fixed number of wavelengths (W), which are consecutive (pre-determined)λ Or : each fiber has a fixed # B, each band has a fixed # of wavelengths and these wavelengths are chosen randomly (not necessarily consecutively) / adaptively — may be more flexible, BUT too complex to realize in practice~10~Vishal AnandVishal AnandWaveband Grouping strategies(1) end-to-end: grouping the lightpaths with the same source-destination pair only; (2) one-end:grouping the lightpaths from the same source only OR grouping the lightpaths with same destination only; (3) sub-path: grouping the lightpaths with common intermediate links (i.e. sub-paths); From any source to any destinationλ Strategy (3) is the most general, BUT also complex~11~Vishal AnandVishal AnandWBS Vs classical Wavelength Routed Networks (WRN)λ Different objectives and techniquesλ WRN: typically minimize wavelengths or wavelength-hops(WH)λ WBS networks: minimize the number of portsλ Minimizing wavelengths does not minimize the num. of portsλ Used an algorithm which optimizes (using Linear Prog.) the used wavelengths by Routing & Wavelength Assignment (RWA), and then does best effort grouping, backfiredλ Caused an increase rather than a decrease in port countλ An ideal WBS algo. may need to trade a slight increase in wavelengths for a much reduced port countλ The WBS optimization problem has more constraints and harder to solve~12~Vishal AnandVishal AnandWBS Vs WRN (cont'd)λ Techniques developed for WRN, traffic grooming cannot be applied directly to address WBS-problemsλ In WRN, traffic grooming is used to reduce (de) mux, electronics, wavelengths and hence costλ WRN: any set of lower bit rate sub-wavelength traffic can be multiplexed onto a wavelengthλ Only constraint is total bit rate ≤ max. bit rate of wavelengthλ E.g. any 12 SONET STS-1 (51.84 Mbps) signals can be multiplexed onto a OC-12 wavelength, as: 12 x STS-1 = 622.08 Mbps = OC-12 (2.5Gbps)λ WBS: at least one more constraintλ Only the traffic carried by afixed set(typically consecutive) can be grouped into a band~13~Vishal AnandVishal AnandPerformance of WBS networks: Static case experimental Resultsλ The problem: λ Given:λ Network topology, number of wavelengths per fiber (F), bands per fiber (B) and granularity (W), network capacity is not fixedλ A set of static traffic demands (i.e. lightpaths) – all given upfrontλ How to satisfy all the traffic using minimum number of ports, when no wavelength conversion is available?λ Approach:1. Optimization using Integer linear Programming (ILP) model, for details Refer [opticomm’02, Infocom’03]λ Not feasible (uses too much time and memory) for large problem sizes2.Heuristic based approach for large problemsλ Based on waveband assignment strategy (3), sub-path grouping~14~Vishal AnandVishal AnandILP formulation for WBS — central ideasλ Objective:λ Minimize the total number of portsλ Minimize the maximum size of a node (i.e. port count)λ Variablesλ Node (i.e. ports therein) is the central point of interestλ Define the property or characteristics of a node instead of a linkcost equalhaveportsall12])[max()(1][⇒===→++→++∑∑∑∑∑∑γβαγβαγβαnnnnnnnnnnnnnFXCBXCWXCMINORFXCBXCWXCMIN~15~Vishal