a reconfigurable wireless datacenter fabric using free...
TRANSCRIPT
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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
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Datacenter network design is hard!
Cost
Performance
Cabling Expandability
Energy
Cooling Adaptability
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Existing Data Center Network Architectures
…
Over subscribed(e.g. simple tree)
Augmented (e.g. cThrough)
…
u
Over provisioned(e.g. FatTree, Jellyfish)
…
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Our Vision : FireFly
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• Coreless
• Wireless
• Steerable
ToRswitch
FireFlyController
SteerableLinks
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Potential Benefits of This Vision
Cost
Performance
Cabling
Expandability
Energy
Cooling
Adaptability
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Wireless
Coreless
Steerable
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Challenges in Realizing the Vision
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FireFlyController
ToRswitch
SteerableFSOs
• Steerable wireless links
• Network Design
• Network Management
FireFly shows this vision is feasible
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Outline
• Motivation
• Steerable Wireless Links
• Network Design
• Network Management
• Evaluation
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Why FSO instead of RF?
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RF (e.g. 60GHZ) FSO (Free Space optical)
Wide beam High interferenceLimited active linksLimited Throughput
Narrow beam Zero interferenceNo limit on active linksHigh Throughput
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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
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Why Size, Cost, Power Can be Reduced?
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• 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)
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FSO Design Overview
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SFP
fiber optic cables
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FSO Design Overview
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SFP
Diverging beam
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FSO Design Overview
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SFP
Lens focal distance
• large cores (> 125 microns) are more robust
Large core fiber optic cables
Parallel beam
lens Focusing lensCollimating lens
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Steerability
Cost
Size
Power
• Not Steerable
FSO design using SFP
Via Switchable mirrorsor Galvo mirrors
Shortcomings of current FSOs
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Steerability via Switchable Mirror
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A
Ceiling mirror
B C
• Switchable Mirror: glass mirror• Electronic control, low latency
SM in “mirror” mode
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Steerability via Galvo Mirror
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A
Ceiling mirror
B C
• Galvo Mirror: small rotating mirror• Very low latency
Galvo Mirror
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FSO Prototype in Data center
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Fiber holder and lens
Mirror
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FSO Link Performance
6 mm 6 mm
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FSO link is as robust as a wired link
• Effect of vibrations, etc.
• 6mm movement tolerance
• Range up to 24m tested
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Outline
• Motivation
• Steerable Wireless Links
• Network Design
• Network Management
• Evaluation
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How to design FireFly network?
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• 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
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FireFly Network Design
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• # 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
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Outline
• Motivation
• Steerable Wireless Links
• Network Design
• Network Management
• Evaluation
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Network Management Challenges
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• Reconfiguration
– Traffic engineering
– Topology control
• Correctness during flux
ToRswitch
FireFlyController
SteerableFSOs
Ceiling Mirror
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FireFly Reconfiguration Algorithm
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• 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
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Correctness Problems During Flux
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• Connectivity
• Black Holes
• Latency A BA BA B
C CC
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Simple Rules To Ensure Correctness
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• 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
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Outline
• Motivation
• Steerable Wireless Links
• Network Design
• Network Management
• Evaluation
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FireFly Evaluation
• Packet-level
• Flow-level (for large scale networks)
• Evaluation of network in-flux
• Evaluation of Our Heuristics
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02468
10
hotspot (8) hotspot (16) Uniform
fireFly cThrough Fattree i
Thro
ugh
pu
t p
er s
erve
r in
Gb
ps
Htsim simulator, 64 racks, three traffic patterns
FireFly is comparable to FatTree with less than ½ the ports
Flow completion time better than FatTree
FireFly Throughput
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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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