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Optical PacketOptical Packet--SwitchedSwitched

WDM Networks:WDM Networks:

a Cost and Energy Perspectivea Cost and Energy Perspective

Rodney S. Tucker

ARC Special Research Centre for Ultra-Broadband Information Networks (CUBIN)

University of Melbourne

[email protected]

Acknowledgements: Jayant Baliga, Kerry Hinton, Rob Ayre, Gangxiang Shen, Wayne Sorin

Australian Research Council, Cisco

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SummarySummary

Optical packet-switched networks

Network architectures

- Point-to-point WDM IP networks

- IP networks with optical grooming

- Optical burst switching

- Optical packet switching

CAPEX and network architectures

- Scaling

Energy consumption and network architectures

- Core and access networks

Disclaimers:- Numbers given here are approximate - YMMV

- OPEX not included

E-mail me for copies of these slides

Impact onnetwork growth

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EdgeRouters Optical PacketOptical Packet--Switched WDM NetworkSwitched WDM Network

1 h o p

Is this simple model realistic?

IP PacketsCore Router

OXC

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Patent(s) Pending andCopyright © LumetaCorporation 2007

The Reality: Map of the InternetThe Reality: Map of the Internet

Not Included:

• Enterprise Networks

• Content Distribution Networks

• Data Centres

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Number of Hops in the InternetNumber of Hops in the Internet

0 5 10 15 20 250

0.02

0.04

0.06

0.08

0.1

Number of Hops, k

]

P r

H

k =

Source: P. Van Mieghem,

“ Performance Analysis of Computer Systems and Networks” , Cambridge (2006)

2006 Data

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Optical

Burst

Switching

(OBS)

Evolution of Optical PacketEvolution of Optical Packet--Switched NetworksSwitched Networks

Capacity

Time

Point-to-PointWDM (P2P)

OpticalCircuit

Switching

(OCS)

Stage 1

CAPEX?

Energy Consumption?Optical

Packet

Switching

(OPS)

““ConventionalConventional”” WisdomWisdom

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1. Point1. Point--toto--Point WDM NetworkPoint WDM Network

Router provides

sub-wavelength groomingby statistical multiplexing

Lightpath

Fiber O/E/O Converters

Core

Router

O/E/O

Converters

Access Routers

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EdgeRouters

Core Router

1 h o p

OXC

2. Optical IP Network2. Optical IP Network

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2. Optical IP Network2. Optical IP Network

Lightpath

OXC/ROADM

Core

Router Fiber

• Optical bypass

• Sub-wavelength grooming

O/E/O Converters

O/E/O

Converters

Access Routers

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3. Waveband IP Network3. Waveband IP Network

MUX

• Waveband grooming

• Optical bypass

• Sub-wavelength grooming

Lightpath

Fiber

Waveband

OXC/ROADM

Access Routers

O/E/O ConvertersCore

Router

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Consider three network architectures:

Cost and Scalability of Optical NetworksCost and Scalability of Optical Networks

Compare CAPEX

Parthiban et al., 2003

Number of users: 10 million

P2P WDM Optical IP Waveband IP

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Input ParametersInput Parameters

Capacities:

Router: 5 – 90 Tb/s

OXC: 1000 ports

Lightpath: 40 Gb/s

Fiber: 250 lightpaths

250 λ

1 λ = 40 Gb/s

1000 1000

Average Access rate per user: 1 - 100 Mb/s 10 million users

Component costs [Ferreira 02, Sengupta 03] OXC, router – chassis, port

Fiber, amplifiers, lightpath terminations

Ignore

Access network, search engines, data centers, etc. Optical impairment cost – e.g. regenerators

Protection & restoration

Multiple domains

Cost reductions as technology matures OPEX

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ResultsResults – – Network CostNetwork Cost

1

102

104

1010 100

Average Access Rate (Mb/s)

C o s t p

e r U s e r ( $ )

Parthiban et al., 2003

P2P WDM

Optical IP

Waveband IP

Today’s Internet(~ 100 kb/s)(Access rate per user in a busy period)

S l o p e

= 1

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Cumulative Internet Capex (North America)

0

10

20

30

40

50

60

70

80

90

2000 2005 2010

Total

Core and

Metro

Access

Optical transport

Year

C u m u l a

t i v e C a p e x

$ B i l l i o n s

Based on data from Nemertes Research, 2007

~$400 / user

Sanity CheckSanity Check

150 million users

Nemertes, November 19, 2007:“User demand could outpace network capacity by 2010

$137 billion global infrastructure investment needed”

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• Optical IP network

– Can save costs in today’s network

– Optical bypass reduces router ports

• Waveband IP network

– Eliminates the bottleneck in number of ports and lightpaths

– Least costly for high access rates

• There is no such thing as a free lunch

– If you want more bandwidth, you will have to pay for it

ObservationsObservations

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Energy Consumption of the NetworkEnergy Consumption of the Network

Power In

• Greenhouse Impact• Managing “Hot Spots”

- Getting the energy in- Getting the heat out

• Energy-limited capacity bottlenecks

Why worry about energy consumption?

• OPEX

Hot spot

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Metro

Core

Edge Edge

Curb Curb Curb Curb

Core Core

Access

Core

ONU ~ 5-10W

OLT - 100W

CRS-1

~ 10 kW / rack

12816 Edge~ 4 kW

0.1 - 1000 Mb/s to the user

Fibre Amps

WDM

PassiveOptical

Network

Packetover

Sonet

Energy Model of Simple IP NetworkEnergy Model of Simple IP Network

Baliga et al., 2007

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1000

P o w

e r ( W / u s e r )

% o f E l e c t r i c i t y S u p p l y

Baliga et al., 2007

0

20

0.5

25

5


15

4 862

1.0

10

20 hops

Power Consumption of IP NetworkPower Consumption of IP Network

Total

Core

Access +Metro

SDH/WDM Links

Today’s Internet(~ 100 kb/s)

2008 Technology

P C ti f IP N t k

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10000

P o w

e r ( W / u s e r

)

% o f E l e c t r i c i t y S u p

p l y

Baliga et al., 2007

0

150

2.5

200

50


100

40 806020

5.0

7.5

10

Total

Core

Access +Metro SDH/WDM

20 hops

Power Consumption of IP NetworkPower Consumption of IP Network

2008 Technology

Ob ti / Q tiOb ti / Q ti

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• Access network dominates energy consumption at low rates – Standby mode?

• Core network dominates at higher rates

– Reduce hop count?

• What is the bottleneck in the core? Speed or energy?

– Optical packet switching

• Optical transport (WDM) consumes relatively little energy

< 5% of energy

> 25% of CAPEX

• Annual CAPEX / Annual energy OPEX > 2

Observations / QuestionsObservations / Questions

1

3

2

El t i R tEl t i R t

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OpticsElectronics

1

F

1

K

1

Switch Fabrics

F

Buffers

F

Demutiplexers F

Multiplexers

Fibers

Forwarding Engine

J

1

Switch

Fabric

J

O/E

Converters

Reduced bit rate

Electronic Router Electronic Router

P C ti i R tPo er Cons mption in Ro ters

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Router Throughput

P o w e r c o n s u m p t i o

n ( W )

Source: METI, 2006, Nordman, 2007

Power Consumption in RoutersPower Consumption in Routers

10

100

1,000

10,000

100,000

1,000,000

P = C2/3

where P is in Wattswhere C is in Mb/s

10 nJ/bit

100 nJ/bit

1

1 Pb/s

P ~ 10

1 Tb/s1 Gb/s1 Mb/s

?

Energ per Bit in Ro tersEnergy per Bit in Routers

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E n e r

g y p e r B i t ( n J )

Energy per Bit in RoutersEnergy per Bit in Routers

1

10

100

1,000

10,000

100,000

10 nJ/bit

100 nJ/bit

0.1

1 nJ/bit

Router Throughput

1 Pb/s1 Tb/s1 Gb/s1 Mb/s

?

Heat LoadHeat Load

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Year

Source: K. Brill , The Uptime Insti tute

Heat LoadHeat Load

1 nJ/bitAir Cooling Limit

Energy in HighEnergy in High End Electronic RouterEnd Electronic Router

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SwitchFabric

Buffer

I/O

Switch

Control

Data PlaneControl Plane

Line Card

Energy in HighEnergy in High--End Electronic Router End Electronic Router

Routing

Engine

Routing

Tables

Power

supply

inefficiency

Fans andblowers

35%11%32%7% 5% 10%Fractionof Total

Source: G. Epps, Cisco, 2007

Buffer

O/E

Buffer

O/EForwarding Engine

Energy/bit 0.7 nJ 1.0 nJ0.5 nJ3.2 nJ 3.5 nJ1.1 nJ

Forwarding Engine

NetworkNetwork EnergyEnergy Consumption per BitConsumption per Bit

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Total

Metro + Access

Core

0.1 1 10 100

E n e r g

y p e r b i t ( J

)

10-6

10-3

10-8

10-5

10-7

10-4

20 hops

~1 μJ/b

WDM Links


NetworkNetwork EnergyEnergy Consumption per BitConsumption per Bit

Energy in Electronic Integrated CircuitsEnergy in Electronic Integrated Circuits

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Energy in Electronic Integrated CircuitsEnergy in Electronic Integrated Circuits

CMOS Gates

Cwire

⎡ ⎤= + ⎣ ⎦∑ ∑21

Energy 2gate wireE C V

=Power Energy x Bit Rate

CMOS IC

Diversion:Diversion: CapacitanceCapacitance of the Core Networkof the Core Network

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Diversion:Diversion: CapacitanceCapacitance of the Core Networkof the Core Network

30 F (North America) Network C ≈

300 F (Global) Network C ≈

Source

→ = × 8~ 150 million users 200 nF 1.5 10Network

C x

50% efficiency

Energy per bit per user: 212

E C V ⎡ ⎤= ⎣ ⎦∑= = → ≈

∑

1 μJ2, 200 nF

2V E C

V Destination

Capacitance

per user

C1 C2

Energy Consumption in Access NetworksEnergy Consumption in Access Networks

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NEC CM7710T

Splitter PON

FTTN

PtP

WiMAX

Cabinet

Edge Node

Cisco

12816 NECCM7700S

Zyxel

VES-1616F-34Cisco

4503

NEC VF200F6

NEC GM100

Axxcelera

ExcelMax CPE

Axxcelera

ExcelMax BTS

Cabinet

Baliga et al., OThT6

Access N/W


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Baliga et al., OThT6


• Wireless access consumes more energy than optical access• PON FTTH is “greener” than FTTN

• “Standby mode” shows significant potential (OThT6)

E n e r g y p e r b

i t ( J )

WiMAX

FTTN

PtP

PON10-7

10-5

10-8

10-6

1 10 100 1000


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Stage 1

Time

Optical Burst

Switching

(OBS)

Point-to-

Point WDM

(P2P)

Stage 2

Optical

Packet

Switching

(OPS)

Capacity

Evolution of Optical PacketEvolution of Optical Packet Switched NetworksSwitched Networks

Optical

CircuitSwitching

(OCS)

CAPEX and

Energy Barrier

All-optical

sub-wavelength

grooming

Stage 2 EvolutionStage 2 Evolution –– OCS to OBSOCS to OBS

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Burst Assembly Router

Core Router

Edge

Router

Stage 2 EvolutionStage 2 Evolution OCS to OBSOCS to OBS

Access

Routers

Edge Node

OXC

Electronics

WDM Link

Optical Burst

Switches

Optical Burst Switched NetworkOptical Burst Switched Network

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Optical Burst Switched NetworkOpt ca u st S tc ed et o

t

Optical Burst SwitchNo Buffering

IP Packets

Burst Assembly

Router

IP Packets (duration < μs)

Data Bursts (duration < ms)

Headers

Offsett

C. Qiao and M. Yoo, JHSN, 1999

Optical Burst SwitchingOptical Burst Switching

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p gp g

Source Destination

D

AT

A

Offset

Burst

length

< ms

Header

Time

Distance

Switch 1 32 4 5

Normalized Cost: OBS vs. IPNormalized Cost: OBS vs. IP

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N o r m a l i z e

d C o s t

20

With wavelength conversion

10-6 10-5 10-4 10-3 10-2 10-1

5

0

10

Average Path Blocking Probability

15

Waveband IP

OBS

Without wavelength conversion

1 Gbit/s Access Rate

Optical IP

Parthiban et al., OFC 2005

Why is OBS more Costly?Why is OBS more Costly?

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y yy y

Waveband

MUX

OBS

DEMX

Waveband

Wavelengths Wavelengths

Bursts Bursts

• Requires increased number of lightpaths for a given blocking probability

• Switch technology requires fast reconfiguration time: More costly per port than “slow” OXC’s (MEMS etc.)

Solution: Waveband Burst Switching (WBS)Solution: Waveband Burst Switching (WBS)

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Burst

Waveband

WBS

Waveband Route

λ

t

Pro’s:

• Requires fewer OXC ports

Con’s:• OXC ports must be wideband

• Requires waveband (i.e. multi-channel) wavelength conversion

• Dispersion issues

Waveband

Y. Huang et al., OFC 2004, Pathiban et al., OFC 2006

Waveband Burst Switching (WBS)Waveband Burst Switching (WBS)

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Average Path Blocking Probability

N o

r m a l i z e d C o s t

5

Optical IP

Waveband IP

10-2 10-1

WBS (WC) + Deflection Routing +Burst Segmentation

WBS with wavelength conversion

3

1

7

Parthiban et al., OFC 2006

1 Gbit/s Access Rate

10-5 10-4 10-3 10-2 10-1


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Stage 1

Stage 2

Time

OpticalBurst

Switching

(OBS)

Optical

Packet

Switching

(OPS)

Point-to-

Point WDM

(P2P)

Optical

CircuitSwitching

(OCS)

Stage 3Capacity

Optical PacketOptical Packet--Switched NetworkSwitched Network

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• Will a viable optical buffering technology emerge?

• Can OPS reduce energy consumption?

Optical PacketSwitches

With Buffering

Access Router

The “Holy Grail” of Optical Networking

OXC

Optical Packet Switch (OPS)Optical Packet Switch (OPS)

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Demutiplexers

1

F

1

K

Wavelength-

Interchanging

Cross Connect +

Header Replacement

F

Output Buffers

1

ForwardingEngine

Input SynchronizersMutiplexers

Electronics Optics

12

Optical Buffer StructuresOptical Buffer Structures

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Delay

Delay

Delay LineVariable

Delay Line

Cross Point

RecirculatingLoop

StaggeredDelay LineDelay

D el a y

Control

Cross Point

Cross Point

Optical Fiber BuffersOptical Fiber Buffers

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.

Cisco CRS-1 with 1000 ports,250 ms buffering per port

OPS with 1000 ports,250 ms buffering per portoptical fiber delay lines

Total buffer capacity of 104 Gigabits

~ 103 RAM chips

Cost < US$ 50k

Buffer power dissipation < 1 kW

Total fibre length = 40 Gm

150 times distance from Earth to Moon!

Reduced Buffer SizeReduced Buffer Size

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Total fibre length = 1000 km~5 μs (~20 packets) buffering per port

Loss per port = 0.2 dB

Loss per port = 33,000 dB

Optical fiber delay lines

Planar waveguide or slow light delay lines

(0.1 dB/cm)

Minimum feasiblebuffer size?

Loss Energy

Tucker, PS 2007

Holographic BuffersHolographic Buffers

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Input image

Output image

Reference beam

Orlov et al., Proc IEEE, 2004Psaltis, CLEO 2002

Ashley et al. IBM J. Res. Dev., May 2000

Read speeds up to 10 Gb/s

Holographic Medium:

Photorefractive material(e.g LiNbO3, polymers)

Write speeds up to 1 Gb/s

Storage

density

Retention

time

Access

TimeWrite Time

∞ > 500 μs1/λ3 ~ 50 μs

Comparison of Optical Buffer TechnologiesComparison of Optical Buffer Technologies

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Show stopper

Challenge

Technology Fiber

Planar WG,

Slow Light

Optical

Resonator Holographic CMOS

Access

Time

Structure-

dependent

Structure-

dependentSmall ~ 50 μs 200 ps

Retention

Time > 500 μs < 5 μs 1-100 ns ∞ 64 ms

Capacity

(Packets)> 2,000 < 20 << 1 ∞ ∞

Energy/bit ~ 1 fJ ~ 1 pJ ~ 1 pJ ~ 1 pJ ~ 1 fJ

Physical

Size

Very

LargeMedium Medium Small

Very

Small

Chirp

Sensitivity No Small Large Large No

Tucker, PS 2007

Packet Switch CrossPacket Switch Cross--Connect TechnologiesConnect Technologies

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Optical

Interconnects

Chips

AWG’sWavelength

Converters

AWG-Based CMOS

SOA-Based

~10 pJ/bit~5 pJ/bit

>100 pJ/bit

3-stage Clos

(2 pJ/bit)

(1 pJ/bit)

(1.5 pJ/bit)

(10 pJ/bit per gate)

Tucker, JLT 2005, OSN 2008

Projected Energy Consumption

Benes

Benes Array

Observations on Optical Packet SwitchingObservations on Optical Packet Switching

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• No viable optical buffering technology in sight

• Optical switch fabrics may become competitive with CMOS

• Not clear whether optical packet switching will solve the energybottleneck problem

Summary

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• Optical bypass reduces CAPEX and energy consumption- Promising future for optical cross-connects and ROADMs

• Energy bottleneck in routers is looming

- More significant than the so-called “electronic speed bottleneck”

• Can optical packet switching overcome the energy bottleneck?

- Optical buffering is currently a show-stopper

• Think “Energy per Bit”

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