Transcript A Survey on Optical Interconnects for Data Centers

A Survey on Optical Interconnects for
Data Centers
Speaker: Shih-Chieh Chien
Adviser: Prof Dr. Ho-Ting Wu
Outline
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Introduction
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Current Data Center
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Network traffic characteristics
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Optical technology
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Architectures
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Comparison
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Conclusion
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Reference
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Introduction
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Internet traffic
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Emerging application
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e.g. Stream video, Social network, Cloud computing
Data-intensive
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e.g. cloud computing, search engines, etc.
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High interaction(servers in the data center)
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Power consumption(inside the rack)
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each rack must the same → thermal constraints
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Blade server
資料來源:wikipedia
Rack mount
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Introduction (cont.)
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Introduction (cont.)
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IT power percentage
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Server 40%, Storage 37%, Network devices 23%
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Include HVAC (Heating-Ventilation and Air-Conditioning)
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ICT GHG from 14% to 18%(2007 ~ 2020)
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Goal
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High throughput, reduced latency, low power consumption
→ Using optical network
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Introduction (cont.)
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Optical network
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Opaque networks (older telecom. network)
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OEO(optical-electrical-optical)
Main draw back is power hungry
all-optical networks (currently)
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Device
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Optical cross-connects (OXC)
Reconfigurable optical add/drop multiplexers(ROADM)
Point-to-point links( based on multi-mode fibers)
Provide 75% energe saving
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Current DC with commodity switches
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Data center
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3 tiers
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Core switches, Aggregate switches, and ToR
Advantage
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Scaled easily
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Fault tolerant
DrawBack
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High power consumption
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High number of links required
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Current DC with commodity switches
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Data center
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3 tiers
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Core switches, Aggregate switches, and ToR switches
Advantage

Scaled easily
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Fault tolerant
DrawBack
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High power consumption
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High number of links required
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Fat-tree
Core level
Aggregate level
資料來源:wikipedia
Access level
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ToR switch
…
1Gbps links
資料來源:IBM
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Current DC with commodity switches
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Data center
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3 tiers

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Core switches, Aggregate switches, and ToR
Advantage

Scaled easily

Fault tolerant
DrawBack

High power consumption

High number of links required
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Current DC with commodity switches
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Data center

3 tiers



Core switches, Aggregate switches, and ToR
Advantage

Scaled easily

Fault tolerant
DrawBack

High power consumption

High number of links required
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Network traffic characteristics
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Three classes (categorized by Microsoft research)
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University campus DC
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private enterprise DC
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cloud-computing DC
Model traffic
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Interarrival rate distribution of the packet
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Lognormal distribution (in the private DC)
Weibull distribution (in the campus DC)
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Network traffic characteristics
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Three classes (categorized by Microsoft research)
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University campus DC
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private enterprise DC
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cloud-computing DC
Model traffic
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Interarrival rate distribution of the packet
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Lognormal distribution (in the private DC)
Weibull distribution (in the campus DC)
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Network traffic characteristics (cont.)
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Main empirical findings
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Applications
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e.g. HTTP, HTTPS, LDAP, Database。
Traffic flow locality
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Inter rack traffic 10%~80%
Intra rack traffic
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Traffic flow size and duration
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Concurrent traffic flows
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Packet size
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Link utilization
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Optical Technology
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Splitter and combiner
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Coupler
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Arrayed-Waveguid Grating(AWG)
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Wavelength Selective Switch(WSS)
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Optical Technology (cont.)
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Micro-Electro-Mechanical Systems Switches(MEMSswtch)
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Semiconductor Optical Amplifier(SOA)
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Tunable Wavelength Converters(TWC)
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Architectures (C-Through)
Electrical network
Optical network
Rack servers
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Architectures (C-Through (cont.))
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Hybrid electrical-optical network
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Traffic monitoring system
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Optical configuration manager
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Traffic in the ToR switch
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Demutiplexed by VLAN-based routing
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Packet based and circuit based network
Evaluation
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Reduce completion time of the application
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Reduce latency between two nodes
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Comparison
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Technology
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All optical interconnection
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Hybrid interconnection
Connectivity
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Circuit based switching
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Based on MEMS switch
Packet based switching
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Array fixed lasers
Fast tunable transmitters
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Comparison Hybrid & all-optical
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Comparison
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Technology
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All optical interconnection
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Hybrid interconnection
Connectivity
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Circuit based switching
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Based on MEMS switch
Packet based switching
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Array fixed lasers
Fast tunable transmitters
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Comparison(connectivity)
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Comparison(cont.)
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Scalability
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Constrained by what?
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Number of switch optical port
Number of wavelength channels
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Capacity
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Routing
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Prototypes
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Comparison(scalability)
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Comparison(cont.)
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Scalability
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Constrained by what?
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Number of switch optical port
Number of wavelength channels
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Capacity
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Routing
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Prototypes
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Comparison(capacity)
Capacity limitation technology
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Comparison(cont.)
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Scalability
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Constrained by what?
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Number of switch optical port
Number of wavelength channels
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Capacity
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Routing
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Prototypes
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Comparison(cont.)
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Scalability
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Constrained by what?
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Number of switch optical port
Number of wavelength channels
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Capacity
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Routing
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Prototypes
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Comparison(prototype)
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Cost and power consumption
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Commercially available (lower price)
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c-Through, Helios, and Proteus (optical modules)
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Data-vortex, and DOS (SOA modules)
Intresting thing
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OPEX (operation cost)
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CAPEX(equipment's cost)
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Cost and power consumption(cont.)
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Simulation
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Replacement of current switches
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Data center with 1536 servers
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Two-tier topology
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512 ToR switches
16 aggregate switches (32x10 Gbps ports) →each arround $5k
Power consumption will be 77kW
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Cost = OPEXCDCN − (CAPEXOI + OPEXOI)
where,
CDCN : CurrentDataCenterNetwork
OI : OpticalInterconnects
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Conclusion
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Optical interconnets (promising solution for DC)
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High BW, low latency , and reduced energy consumption
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Hybrid proposed as an upgrade to current networks
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Schemes based on SOA for switching
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Faster reconfiguration time than MEMS switches
Proteus shows high performance optical networks with
readily available optical componetnts
Schemes based on SOA and TWC
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Provide higher capacites and better scalability
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Reference
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http://www.hirose.co.jp/cataloge_hp/e83001002.pdf
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http://www.answers.com/topic/optical-switch
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
G. Wang, D. G. Andersen, M. Kaminsky, K. Papagiannaki, T. E. Ng, M.
Kozuch, and M. Ryan, “c-Through: Part-time Optics in Data Centers,” in
Proc. ACM SIGCOMM 2010 conference on SIGCOMM, ser.
SIGCOMM ’10, 2010, pp. 327–338.
Kachris, Christoforos; Tomkos, Ioannis; , "A Survey on Optical
Interconnects for Data Centers," Communications Surveys & Tutorials,
IEEE , vol.14, no.4, pp.1021-1036, Fourth Quarter 2012
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