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FireFly: A Reconfigurable Wireless Datacenter Fabric using Free-Space Optics

FireFly: A Reconfigurable Wireless Datacenter Fabric using Free-Space Optics. Navid Hamedazimi , Zafar Qazi , Himanshu Gupta, Vyas Sekar, Samir Das, Jon Longtin , Himanshu Shah, Ashish Tanwer. ACM SIGCOMM 2014. Datacenter network design is hard!. Performance. Cost. Energy.

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FireFly: A Reconfigurable Wireless Datacenter Fabric using Free-Space Optics

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  1. FireFly: A Reconfigurable Wireless Datacenter Fabricusing Free-Space Optics Navid Hamedazimi,Zafar Qazi, Himanshu Gupta, Vyas Sekar, Samir Das, Jon Longtin, Himanshu Shah, Ashish Tanwer ACM SIGCOMM 2014

  2. Datacenter network design is hard! Performance Cost Energy Cabling Expandability Cooling Adaptability

  3. Over provisioned (e.g. FatTree, Jellyfish) Existing Data Center Network Architectures Over subscribed (e.g. simple tree) Augmented (e.g. cThrough) u … … …

  4. Our Vision : FireFly ToR switch • Coreless • Wireless • Steerable Steerable Links FireFly Controller

  5. Potential Benefits of This Vision Performance Cost Coreless Cabling Wireless Cooling Steerable Energy Expandability Adaptability

  6. Challenges in Realizing the Vision • Steerable wireless links • Network Design • Network Management ToR switch Steerable FSOs FireFly Controller FireFly shows this vision is feasible

  7. Outline • Motivation • Steerable Wireless Links • Network Design • Network Management • Evaluation

  8. Why FSO instead of RF? RF (e.g. 60GHZ) FSO (Free Space optical) Wide beam  High interference Limited active links Limited Throughput Narrow beam  Zero interference No limit on active links High Throughput

  9. Today’s FSO • Cost: $15K per FSO • Size: 3 ft³ • Power: 30w • Non steerable • Current: bulky, power-hungry, and expensive • Required: small, low power and low expense

  10. Why Size, Cost, Power Can be Reduced? • Traditional use : outdoor, long haul • High power • Weatherproof • Data centers: indoor, short haul • Feasible roadmap via commodity fiber optics • E.g. Small form transceivers (Optical SFP)

  11. FSO Design Overview fiber optic cables Diverging beam Lens focal distance Parallel beam Focusing lens Collimating lens lens Large core fiber optic cables SFP • large cores (> 125 microns) are more robust

  12. Steerability • Cost • Size • Power • Not Steerable Shortcomings of current FSOs FSO design using SFP Via Switchable mirrors or Galvo mirrors

  13. Steerability via Switchable Mirror • Switchable Mirror: glass mirror • Electronic control, low latency Ceiling mirror SM in “mirror” mode B C A

  14. Steerability via Galvo Mirror • Galvo Mirror: small rotating mirror • Very low latency Ceiling mirror Galvo Mirror B C A

  15. FSO Prototype in Data center Mirror Fiber holder and lens

  16. FSO Link Performance 6 mm 6 mm • Effect of vibrations, etc. • 6mm movement tolerance • Range up to 24m tested FSO link is as robust as a wired link

  17. Outline • Motivation • Steerable Wireless Links • Network Design • Network Management • Evaluation

  18. How to design FireFly network? • Goals: Robustness to current and future traffic • Budget & Physical Constraints • Design parameters • Number of FSOs? • Number of steering mirrors? • Initial mirrors’ configuration • Performance metric • Dynamic bisection bandwidth 18

  19. FireFly Network Design • # of FSOs = # of Servers • # of Switchable Mirrors = [10-15] for up to 512 racks or • # of Galvo Mirrors = 1 per FSO • Mirror Configuration = Random graph • less than ½ the ports of FatTree Projected Cost: 40% to 60% lower than FatTree 19

  20. Outline • Motivation • Steerable Wireless Links • Network Design • Network Management • Evaluation

  21. Network Management Challenges Ceiling Mirror • Reconfiguration • Traffic engineering • Topology control • Correctness during flux ToR switch Steerable FSOs FireFly Controller 21

  22. FireFly Reconfiguration Algorithm • Joint optimization problem • Decouple • Traffic engineering • Topology control • Above is done periodically • In addition: Trigger-based reconfiguration • E.g. Create direct link for large flows • Massive ILP • Max-flow, greedy • Weighted Matching

  23. Correctness Problems During Flux C C C A B B B A A • Connectivity • Black Holes • Latency

  24. Simple Rules To Ensure Correctness • Disallow deactivations that disconnect the network. • Stop using a link before deactivating it • Start using a link only after activating it • “Small” gap between reconfigurations

  25. Outline • Motivation • Steerable Wireless Links • Network Design • Network Management • Evaluation

  26. FireFlyEvaluation • Packet-level • Flow-level (for large scale networks) • Evaluation of network in-flux • Evaluation of Our Heuristics

  27. FireFly Throughput FireFly is comparable to FatTree with less than ½ the ports Flow completion time better than FatTree

  28. Conclusions • Vision: Extreme DC network architecture • Fully Steerable, No core switches, All-wireless inter-rack • Unprecedented benefits: • No Cabling, Adapt to traffic patterns, Less clutter • Firefly shows a viable proof point • Practical steerable FSO for datacenters • Practical network design and management heuristics • Close to fat tree performance over several workloads • Less than half of FatTree ports • Just a start .. Many directions for improvement

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