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Optical Packet Switching Techniques

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/. Overview. Introduction and motivations Goals of the thesis

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Optical Packet Switching Techniques

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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/

  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

  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

  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

  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

  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

  7. Goals • New optical network simulator Topology Simulation Performance

  8. Goals • New analysis and design method for optical networks Resources Analysis Topology

  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

  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

  11. Storing data • Optical RAM is not available yet • Fiber Delay Lines (FDLs) are used instead FDLs FDL Forward usage Feedback usage

  12. 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 Processing data l1 l2 3R

  13. Switching data • Today: Semiconductor Optical Amplifiers • Tomorrow (a possibility): Micro Electro Mechanical Systems

  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

  15. The starting simulator: CLASS • Simulator of ATM networks • Topology independent Adaptabletool • Fixed routing implementation • Not good for WDM } fiber channel

  16. } fiber channel CLASS modifications • Dynamic routing strategy • Each WDM channel must be listed in the network description file Maximum flexibility in the network description

  17. 3R 3R 3R 1 1 3R 2 2 3R m m 3R 1 1 n-1 n-1 n n 3R 3R 3R SWITCH CONTROL UNIT SIMON node architecture

  18. Time division • Slotted network: timeslot P 2 C t 1 P C 1 t 2 C t 3 t t 0 1

  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

  20. Designing WDM networks • Given: Network topology and the traffic matrix • Find: Number of WDM channels on each link • Optimizing: Network throughput • Meeting acost constraint: Network cost  commutation Fixed number of ports for all the switches

  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

  22. Proposed approach 1) Find: • Ptot : packet loss probability of the whole network • ni : number of WDM channels on link i 2) Elaborate a heuristic solution to find the minimum of Ptot

  23. Link model • Classical queueing theory: M/M/L/kqueue • server  WDM channel • buffer slot  FDL k 1 2 buffer L servers more

  24. Node model Input fibers Output fibers

  25. Model limitations • 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 FDL B A channel

  26. Network model • The packet loss probability (Pf) of a flow is: • The packet loss probability (Ptot) of the whole network results: • First step completed

  27. Searching the minimum • Cost constraint: (channel ports + FDLs ports) = constant • optimum balance  optimum solution Storage capacity (number of FDLs) Level Network connectivity (number of channel ports)

  28. Heuristic approach • Starting topology: maximum connected • Iteration steps: • the current topology is perturbed • if the perturbed topology has a lower Ptot the topology is modified Highest possible level

  29. Heuristic approach • Topology perturbation: • all the links are analyzed added cancelled • the link that modified gives the lower Ptot is memorized

  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

  31. General backbone: topology Node 6 7 User 5 1 2 8 12 4 3 9 11 10

  32. General backbone: throughput 1 0.95 Fraction of packets successfully transferred 0.9 l 1 l 2 l 3 l 4 M/M/L/k (4 MR) ¥ M/M/L/k ( MR) 0.85 0 2 4 6 8 10 12 14 16 18 Total network load [Gbps]

  33. General backbone: delay 9 8 l 1 l 2 7 l 3 l 4 M/M/L/k (4 MR) 6 ¥ M/M/L/k ( MR) 5 Packets net delay 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 Total network load [Gbps]

  34. USA backbone: topology 1 23 17 8 5 9 14 22 2 4 6 10 15 18 24 25 19 16 11 3 26 20 7 12 27 13 21 28

  35. USA backbone: throughput 1 0.98 0.96 0.94 Fraction of packets successfully transferred 0.92 0.9 l 1 l 2 l 3 0.88 M/M/L/k (4 MR) ¥ M/M/L/k ( MR) 0.86 0 5 10 15 20 25 30 35 40 Total network load [Gbps] more

  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

  37. E S

  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

  39. Link model • Packet loss probability P on the link: • m link capacity • a link traffic load • offered load [Erlangs], continue

  40. Japan backbone: topology 1 2 3 4 5 6 8 7 9 10 11

  41. Japan backbone: throughput 1 0.99 0.98 0.97 0.96 Fraction of packets successfully transferred 0.95 0.94 0.93 l 1 l 2 0.92 l 3 M/M/L/k (4 MR) 0.91 ¥ M/M/L/k ( MR) 0.9 0 5 10 15 20 25 30 Total network load [Gbps] continue

  42. Future work • Simulator: • Support for different architectures • FDLs of variable length • Heuristic approach: • More detailed model for FDLs continue

  43. End of presentation

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