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1 Optical Packet Switching Techniques Walter Picco MS Thesis Defense December 2001 Fabio Neri, Marco Ajmone Marsan Telecommunication Networks Group http://www.tlc-networks.polito.it/
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2 Overview Introduction and motivations Goals of the thesis State-of-the-art and enabling technologies SIMON: an optical network simulator Optical networks design Obtained results
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3 The need of optics Future network requirements: High bandwidth capacity Flexibility, robustness Power supply and equipment footprint reduction Optics offers a good evolution perspective
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4 Optical framework today Point to point communications Circuit switching with packet switching electronic control why ? Optical packet switching: –no optical memories –slow optical switches
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5 Optical packet switching Bandwidth is not a problem Network cost is in the commutation New protocols and architectures needed New tools to measure performance New design techniques more
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6 Overview Introduction and motivations Goals of the thesis State-of-the-art and enabling technologies SIMON: an optical network simulator Optical networks design Obtained results
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7 Goals New optical network simulator TopologySimulationPerformance
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8 Goals New analysis and design method for optical networks ResourcesAnalysisTopology
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9 Overview Introduction and motivations Goals of the thesis State-of-the-art and enabling technologies SIMON: an optical network simulator Optical networks design Obtained results
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10 Transmitting data Wavelength Division Multiplexing: the huge bandwidth of an optical fiber is divided in many channels (colors) Each channel occupies a different frequency slot
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11 Storing data Optical RAM is not available yet Fiber Delay Lines (FDLs) are used instead FDLs Forward usageFeedback usage FDL
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12 Processing data Electronics limits the speed in data forwarding Optical 3R regeneration (and wavelength conversion) is now possible Physical layer is not a matter of concern All-optical solutions are currently at the study 3R 1 2
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13 Switching data Tomorrow (a possibility): Micro Electro Mechanical Systems Today: Semiconductor Optical Amplifiers
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14 Overview Introduction and motivations Goals of the thesis State-of-the-art and enabling technologies SIMON: an optical network simulator Optical networks design Obtained results
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15 Fixed routing implementation Not good for WDM The starting simulator: CLASS Simulator of ATM networks Topology independent Adaptable tool } fiber channel
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16 CLASS modifications Dynamic routing strategy Each WDM channel must be listed in the network description file Maximum flexibility in the network description } fiber channel
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17 SIMON node architecture
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18 Time division Slotted network: t t t C 1 C 2 C 3 t 0 timeslot P 1 P 2 t 1
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19 Overview Introduction and motivations Goals of the thesis State-of-the-art and enabling technologies SIMON: an optical network simulator Optical networks design Obtained results
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20 Designing WDM networks Given: Network topology and the traffic matrix Find: Number of WDM channels on each link Optimizing: Network throughput Meeting a cost constraint: Network cost commutation Fixed number of ports for all the switches
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21 The optimization problem Mathematical statement: Find minimum (maximum) of a non-linear function in the discrete domain, meeting some constraints NP-complete problem Only heuristic solutions are possible
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22 Proposed approach 1)Find: –P tot : packet loss probability of the whole network –n i : number of WDM channels on link i 2)Elaborate a heuristic solution to find the minimum of P tot
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23 Link model Classical queueing theory: M/M/L/k queue server WDM channel buffer slot FDL k 1 2 L servers buffer more
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24 Node model Input fibers Output fibers
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25 FDLs can’t be modeled as a simple buffer –discrete storage time –noise addition at each recirculation All the FDLs of a node are shared among the different queues Model limitations channel FDL A B
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26 Network model The packet loss probability ( P f ) of a flow is: The packet loss probability ( P tot ) of the whole network results: First step completed
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27 Cost constraint: (channel ports + FDLs ports) = constant optimum balance optimum solution Searching the minimum Network connectivity (number of channel ports) Storage capacity (number of FDLs) Level
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28 Heuristic approach Starting topology: maximum connected Iteration steps: –the current topology is perturbed –if the perturbed topology has a lower P tot the topology is modified Highest possible level
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29 Heuristic approach Topology perturbation: –all the links are analyzed –the link that modified gives the lower P tot is memorized cancelled added
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30 Overview Introduction and motivations Goals of the thesis State-of-the-art and enabling technologies SIMON: an optical network simulator Optical networks design Obtained results
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31 General backbone: topology Node User 12 34 5 67 8 9 1011 12
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32 General backbone: throughput 024681012141618 0.85 0.9 0.95 1 Total network load [Gbps] Fraction of packets successfully transferred 1 2 3 4 M/M/L/k (4 MR) M/M/L/k ( MR)
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33 General backbone: delay 024681012141618 0 1 2 3 4 5 6 7 8 9 Packets net delay 1 2 3 4 M/M/L/k (4 MR) M/M/L/k ( MR) Total network load [Gbps]
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34 USA backbone: topology 28 27 26 25 24 23 22 21 20 19 1815 16 11 10 12 13 17 14 9 8 5 6 7 3 42 1
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35 USA backbone: throughput 0510152025303540 0.86 0.88 0.9 0.92 0.94 0.96 0.98 1 1 2 3 M/M/L/k (4 MR) M/M/L/k ( MR) Total network load [Gbps] Fraction of packets successfully transferred more
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36 Conclusions Two key elements: A new tool capable to simulate the next generation optical networks A new optimization target in the optical networks design giving good results more
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37 E S
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38 Optical Burst Switching Packets are assembled in the network edge, forming bursts Advantages: –More efficient exploitation of the bandwidth –Possibility to implement Service Differentiation Disadvantages: –More complicated network structure –More complicated forwarding process continue
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39 Link model Packet loss probability P on the link: – link capacity – link traffic load – offered load [Erlangs], continue
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40 Japan backbone: topology 1 23 4 5 6 7 8 9 10 11
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41 Japan backbone: throughput 051015202530 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1 1 2 3 M/M/L/k (4 MR) M/M/L/k ( MR) Total network load [Gbps] Fraction of packets successfully transferred continue
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42 Future work Simulator: –Support for different architectures –FDLs of variable length Heuristic approach: –More detailed model for FDLs continue
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43 End of presentation
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