Post on 23-Feb-2016
description
Patch Panels in the Sky:A Case for Free-Space Optics
in Data Centers
Navid Hamed Azimi, Himanshu GuptaVyas Sekar, Samir Das
2
Datacenter network design is hard!
Cost
Performance
Cabling Expandability
Energy
Cooling Adaptability
Over subscribed(tree, leaf spine,…)
3
Performance
Existing ChoicesCost
…
Core
Top of Rack (ToR)
Over subscribed(tree, leaf spine,…)
Existing Choices
…
4
Over provisioned(Fattree, Jellyfish,…)
Performance
Cost
Top of Rack (ToR)
Core
Existing Choices
…
5
Core
Over subscribed(tree, leaf spine,…)
Performance
Cost
Augmented (c-Through , 3D Beam)
Top of Rack (ToR)
Over provisioned(Fattree, Jellyfish,…)
Existing Choices
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Over subscribed(tree, leaf spine,…)
Performance
Cost
Augmented (c-Through , 3D Beam)
Over provisioned(Fattree, Jellyfish,…)
Can we get here?
Our Vision
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…
• Core Coreless
• Wired Wireless
• Static Flexible
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Potential Benefits of This Vision
CostPerformance
Cabling
ExpandabilityEnergyCooling
Adaptability
WirelessCoreless
Flexible
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Challenges in Realizing the Vision
• Flexible wireless links
• Network management
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Outline
• Flexible wireless links
• Network management
• Feasibility & cost
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Traditional RF is not Sufficient
…
• Wide beam High interference
Traditional RF is not Sufficient
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…
• Wide beam• Difficult to narrow
High interference
Solution: Free Space Optical Links (FSOs)
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• No interference• High throughput over long range
…
• Easy to narrow beam
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Concerns with FSOs
• Cost : $30K• Size : 3 ft³• Power: 60w• Flexibility
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Why Size, Cost, Power Can be Reduced?
• Traditional use : outdoor, long haul‒ High power‒ Weatherproof
• Data centers: indoor, short haul‒ Low power
• Feasible roadmap via commodity fiber optics ‒ E.g. Small form transceivers (Optical SFP)
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Proof of Concept (1 Gbps)
Fiber connectedto SFP (TX)
Lens LensMirror Mirror
SFP (RX)
SFP : 2x$40Lens : 2x$30
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<924 924- 928 928- 932 >932 Mbps
0
0.2
0.4
0.6
0.8
1Optical fiberFSO
FSO Link ThroughputPDF
Throughput
FSO link is the same as optical cable
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FSO Link Misalignment Tolerance• Effect of vibrations, etc.
Movement tolerance– 0.7mm at destination– 3mm at source
3 mm 0.7 mm
FSO link is stableTX RX
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• Cost : $30K• Size : 3 ft³• Power: 60w• Flexibility
FSOs (1Gbps)
• Cost : $140• Size : 1x4 in• Power: 0.3w• Flexibility
Flexibility via Switchable Mirror
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Sender
Ceiling Mirror
Receiver 1 Reciever2
• Switchable Mirror: glass mirror• Electronic control, low latency
SM in “mirror” mode
Flexibility via Switchable Mirror
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Sender
Ceiling Mirror
Receiver 1 Reciever2
SM in “mirror” mode
Receiver 1 Reciever2
• Switchable Mirror: glass mirror• Electronic control, low latency
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Outline
• Flexible wireless links
• Network management
• Feasibility & cost
Management: Pre-ConfigurationInput: FSO#, SM#,…
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Sender
Receiver 1 Reciever2
Output: Candidate links (Alignment of each SM)
Management: Reconfiguration
Input: Traffic
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Sender
Receiver 1 Reciever2
Output: Run-time topology
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Current Solutions: Simple Heuristics
• Pre-Configuration : Regular Random Graph
• Reconfiguration
Only reconfigure for large flows Only delete a link if network remains connected
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Outline
• Flexible laser link
• Management
• Feasibility & cost
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Throughput• 512 racks, 48 server/rack, hotspots traffic, flow level simulations
(4,5) (4,10) (8,5) (12,5) (8,10) (16,5) (12,10) (16,10)0
0.5
1
1.5
2Fattree 2G 3D-Beamforming
c-through FSO
(Hot Spots %, Average Load per Hot spot (Gbps))
Ave
rage
Thr
ough
put
Per S
erve
r (G
bps)
FSO based 2-4x improvement
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Cost ComparisonArchitecture Cost Effective Bisection
BandwidthFattree 1 Gbps $ 13 M 1 GbpsFSO based $ 38 M 8.5 GbpsFattree 10 Gbps $ 57 M 10 Gbps
FSO based: Near 10G performance with 65% of cost
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Conclusions• Data center network is challenging
• Our vision: Fully flexible, coreless, wireless network
• Key enablers : FSO + switchable mirrors
• Early promise: ~ 10Gbps performance @ 65% cost
• Future work: Improve FSO, better management