Embed Size (px)
Citation preview
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
6
Over subscribed(tree, leaf spine,…)
Performance
Cost
Augmented (c-Through , 3D Beam)
Over provisioned(Fattree, Jellyfish,…)
Can we get here?
Our Vision
7
…
• Core Coreless
• Wired Wireless
• Static Flexible
8
Potential Benefits of This Vision
CostPerformance
Cabling
ExpandabilityEnergyCooling
Adaptability
WirelessCoreless
Flexible
9
Challenges in Realizing the Vision
• Flexible wireless links
• Network management
10
Outline
• Flexible wireless links
• Network management
• Feasibility & cost
11
Traditional RF is not Sufficient
…
• Wide beam High interference
Traditional RF is not Sufficient
12
…
• Wide beam• Difficult to narrow
High interference
Solution: Free Space Optical Links (FSOs)
13
• No interference• High throughput over long range
…
• Easy to narrow beam
14
Concerns with FSOs
• Cost : $30K• Size : 3 ft³• Power: 60w• Flexibility
15
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)
16
Proof of Concept (1 Gbps)
Fiber connectedto SFP (TX)
Lens LensMirror Mirror
SFP (RX)
SFP : 2x$40Lens : 2x$30
17
<924 924- 928 928- 932 >932 Mbps
0
0.2
0.4
0.6
0.8
1Optical fiberFSO
FSO Link Throughput
Throughput
FSO link is the same as optical cable
18
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 stable
TX RX
19
• Cost : $30K• Size : 3 ft³• Power: 60w• Flexibility
FSOs (1Gbps)
• Cost : $140• Size : 1x4 in• Power: 0.3w• Flexibility
Flexibility via Switchable Mirror
20
Sender
Ceiling Mirror
Receiver 1 Reciever2
• Switchable Mirror: glass mirror• Electronic control, low latency
SM in “mirror” mode
Flexibility via Switchable Mirror
21
Sender
Ceiling Mirror
Receiver 1 Reciever2
SM in “mirror” mode
Receiver 1 Reciever2
• Switchable Mirror: glass mirror• Electronic control, low latency
22
Outline
• Flexible wireless links
• Network management
• Feasibility & cost
Management: Pre-ConfigurationInput: FSO#, SM#,…
23
Sender
Receiver 1 Reciever2
Output: Candidate links (Alignment of each SM)
Management: Reconfiguration
Input: Traffic
24
Sender
Receiver 1 Reciever2
Output: Run-time topology
25
Current Solutions: Simple Heuristics
• Pre-Configuration : Regular Random Graph
• Reconfiguration
Only reconfigure for large flows Only delete a link if network remains connected
26
Outline
• Flexible laser link
• Management
• Feasibility & cost
27
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
2
Fattree 2G 3D-Beamforming
c-through FSO
(Hot Spots %, Average Load per Hot spot (Gbps))
Ave
rage
Thr
ough
put
Per
Ser
ver
(Gbp
s)
FSO based 2-4x improvement
28
Cost ComparisonArchitecture Cost Effective Bisection
BandwidthFattree 1 Gbps $ 13 M 1 Gbps
FSO based $ 38 M 8.5 Gbps
Fattree 10 Gbps $ 57 M 10 Gbps
FSO based: Near 10G performance with 65% of cost
29
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
