Optical Packet-Switched WDM Networks - University of Melbourne

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Energy consumption and network architectures. - Core and access ... Content Distribution Networks ... Evolution of Optical Packet-Switched Networks. Capacity.

Optical Packet-Switched WDM Networks: a 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

Summary ƒ

Optical packet-switched networks

ƒ

Network architectures Point-to-point WDM IP networks IP networks with optical grooming Optical burst switching Optical packet switching

ƒ

CAPEX and network architectures Scaling

ƒ

Energy consumption and network architectures Core and access networks

ƒ

Disclaimers: Numbers given here are approximate - YMMV OPEX not included

ƒ

E-mail me for copies of these slides

Impact on network growth

IP Packets

Edge Routers

Core Router

OXC

Optical Packet-Switched WDM Network 1h

op

Is this simple model realistic?

The Reality: Map of the Internet

Patent(s) Pending and Copyright © Lumeta Corporation 2007

Not Included: • Enterprise Networks • Content Distribution Networks • Data Centres

Number of Hops in the Internet 2006 Data

0.1

Pr [ H = k ]

0.08 0.06 0.04 0.02 0

0

5

15 10 Number of Hops, k

20

Source: P. Van Mieghem, “Performance Analysis of Computer Systems and Networks”, Cambridge (2006)

25

Evolution of Optical Packet-Switched Networks “Conventional” Wisdom Capacity CAPEX? Energy Consumption?

Optical Burst Switching (OBS)

Stage 1

Optical Packet Switching (OPS)

Optical Circuit Switching (OCS) Point-to-Point WDM (P2P) Time

1. Point-to-Point WDM Network Lightpath Fiber

O/E/O Converters

Core Router

O/E/O Converters Access Routers

Router provides sub-wavelength grooming by statistical multiplexing

2. Optical IP Network Core Router

Edge Routers

OXC

1h

op

2. Optical IP Network Lightpath Fiber

Core Router

O/E/O Converters

OXC/ROADM

O/E/O Converters Access Routers

• Optical bypass • Sub-wavelength grooming

3. Waveband IP Network Lightpath Waveband Fiber

Core Router

O/E/O Converters

MUX OXC/ROADM • Waveband grooming • Optical bypass • Sub-wavelength grooming Access Routers

Cost and Scalability of Optical Networks Consider three network architectures: P2P WDM

Number of users: 10 million

Parthiban et al., 2003

Optical IP

Waveband IP

Compare CAPEX

Input Parameters ƒ ƒ

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

Capacities: ƒ Router: ƒ OXC: ƒ Lightpath: ƒ Fiber:

5 – 90 Tb/s 1000 ports 40 Gb/s 250 lightpaths

1000

1000 1 λ = 40 Gb/s

250 λ Component costs [Ferreira 02, Sengupta 03] ƒ OXC, router – chassis, port ƒ Fiber, amplifiers, lightpath terminations Ignore ƒ Access network, search engines, data centers, etc. ƒ Optical impairment cost – e.g. regenerators ƒ Protection & restoration ƒ Multiple domains ƒ Cost reductions as technology matures ƒ OPEX

Results – Network Cost 104

Cost per User ($)

P2P WDM

= pe o l S

1

Waveband IP 102 Optical IP

10 Today’s Internet (~ 100 kb/s) Parthiban et al., 2003

1

10 Average Access Rate (Mb/s)

(Access rate per user in a busy period)

100

Sanity Check Cumulative Capex $ Billions

90 80

Cumulative Internet Capex (North America) 150 million users

70

~$400 / user

60 50

Total

40

Core and Metro

30

Optical transport

20 10 0

Access 2000

2005

Year

2010

Nemertes, November 19, 2007: “User demand could outpace network capacity by 2010 $137 billion global infrastructure investment needed” Based on data from Nemertes Research, 2007

Observations •

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

Energy Consumption of the Network Hot spot

Why worry about energy consumption? • OPEX • Greenhouse Impact • Managing “Hot Spots” - Getting the energy in - Getting the heat out • Energy-limited capacity bottlenecks

Power In

Energy Model of Simple IP Network CRS-1 ~ 10 kW / rack Packet over Sonet

Core

Core

Core

Fibre Amps

12816 Edge ~ 4 kW

Metro

WDM

Edge

OLT - 100W

Passive Optical Network

Curb

Edge

Curb Curb

ONU ~ 5-10W

0.1 - 1000 Mb/s to the user Baliga et al., 2007

Core

Curb

Access

Power Consumption of IP Network 25 20 hops

2008 Technology 1.0

Total 15

Today’s Internet (~ 100 kb/s)

Core

10

0.5

Access +Metro 5

SDH/WDM Links 0

0

2

4

6

8

Average Access Rate (Mb/s)

Baliga et al., 2007

10

0

% of Electricity Supply

Power (W/user)

20

Power Consumption of IP Network 10

200 2008 Technology

7.5

Power (W/user)

150

Total 5.0

100

Core 2.5

50

Access +Metro 0

0

20

40

60

SDH/WDM

80

Average Access Rate (Mb/s)

Baliga et al., 2007

100

0

% of Electricity Supply

20 hops

Observations / Questions •

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?

1

– Optical packet switching

3



Optical transport (WDM) consumes relatively little energy < 5% of energy > 25% of CAPEX



Annual CAPEX / Annual energy OPEX > 2

2

Electronic Router Forwarding Engine

1

Fibers 1

1

1

J Switch Fabric

F

F

K F Demutiplexers O/E Converters

Switch Fabrics

Buffers

Reduced bit rate Electronics

Optics

F Multiplexers

Power Consumption in Routers

Power consumption (W)

1,000,000 ?

P = C2/3

100,000

where P is in Watts where C is in Mb/s

10,000 10 nJ/bit 1,000

P ~ 10 100 100 nJ/bit 10 1

1 Mb/s

1 Gb/s

1 Tb/s

Router Throughput

Source: METI, 2006, Nordman, 2007

1 Pb/s

Energy per Bit in Routers 100,000

Energy per Bit (nJ)

10,000 1,000 100 nJ/bit 100 10 nJ/bit 10 ?

1 nJ/bit

1 0.1

1 Mb/s

1 Gb/s

1 Tb/s

Router Throughput

1 Pb/s

Heat Load Air Cooling Limit 1 nJ/bit

Year Source: K. Brill, The Uptime Institute

Energy in High-End Electronic Router Line Card Buffer O/E

Forwarding Engine Switch Fabric

Buffer

I/O

Buffer

O/E

Forwarding Engine

Switch Control

Routing Tables

Routing Engine Control Plane

Data Plane

Power supply inefficiency Fans and blowers

Energy/bit

0.7 nJ

3.2 nJ

0.5 nJ

1.0 nJ

1.1 nJ

3.5 nJ

Fraction of Total

7%

32%

5%

10%

11%

35%

Source: G. Epps, Cisco, 2007

Network Energy Consumption per Bit 10-3 20 hops Energy per bit (J)

10-4 ~1 μJ/b Total

10-5 10-6 10-7

Core Metro + Access WDM Links

10-8 0.1

1

10

Average Access Rate (Mb/s)

100

Energy in Electronic Integrated Circuits

Cwire CMOS Gates CMOS IC

Energy =



Egate +

1⎡ 2⎣



Cwire ⎤ V 2 ⎦

Power = Energy x Bit Rate

Diversion: Capacitance of the Core Network Source

Destination

V

C2

C1

E =1 ⎡ 2⎣

Energy per bit per user: V = 2, E =

1 μJ 2







C ⎤V 2 ⎦

C ≈ 200 nF

Capacitance per user

50% efficiency ~ 150 million users → CNetwork = 200 nF x1.5 × 108

C Network ≈ 30 F (North America)

C Network ≈ 300 F (Global)

Energy Consumption in Access Networks NEC CM7710T

Access N/W Edge Node Cisco 12816

Cabinet Splitter

NEC CM7700S

Cabinet

PON NEC VF200F6

FTTN Zyxel VES-1616F-34

Cisco 4503

NEC GM100

PtP Axxcelera ExcelMax CPE Axxcelera ExcelMax BTS

Baliga et al., OThT6

WiMAX

Energy Consumption in Access Networks WiMAX Energy per bit (J)

10-5

PtP 10-7

10-8

• • •

FTTN

10-6

PON

1

10 100 Average Access Rate (Mb/s)

Wireless access consumes more energy than optical access PON FTTH is “greener” than FTTN “Standby mode” shows significant potential (OThT6)

Baliga et al., OThT6

1000

Evolution of Optical Packet-Switched Networks Capacity Optical Packet Switching (OPS)

Stage 2 CAPEX and Energy Barrier

Stage 1 Point-toPoint WDM (P2P)

Optical Burst Switching (OBS)

All-optical sub-wavelength grooming

Optical Circuit Switching (OCS)

Time

Stage 2 Evolution – OCS to OBS

Core Router Edge Node

Optical Burst Switches Electronics WDM Link

OXC

Edge Router

Access Routers Burst Assembly Router

Optical Burst Switched Network Optical Burst Switch No Buffering

IP Packets (duration < μs)

Data Bursts (duration < ms) IP Packets t Burst Assembly Router

C. Qiao and M. Yoo, JHSN, 1999

Headers Offset

t

Optical Burst Switching Source

Header

Destination

Offset

Time

Burst length < ms

D A T A

Switch

1

2

3

4 Distance

5

Normalized Cost: OBS vs. IP 20

Optical IP

Normalized Cost

1 Gbit/s Access Rate 15

Without wavelength conversion OBS

10 With wavelength conversion 5

Waveband IP

0

10-6

10-5

10-4

10-3

10-2

Average Path Blocking Probability

Parthiban et al., OFC 2005

10-1

Why is OBS more Costly? OBS MUX

Wavelengths

Waveband Bursts

Wavelengths

Bursts

DEMX Waveband



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) Waveband Route λ

Burst

t

WBS Waveband

Waveband

Pro’s: • Requires fewer OXC ports Con’s: • OXC ports must be wideband • Requires waveband (i.e. multi-channel) wavelength conversion • Dispersion issues Y. Huang et al., OFC 2004, Pathiban et al., OFC 2006

Waveband Burst Switching (WBS) 1 Gbit/s Access Rate 7 Normalized Cost

Optical IP 5

WBS with wavelength conversion

3

Waveband IP

1

WBS (WC) + Deflection Routing + Burst Segmentation

10-5

Parthiban et al., OFC 2006

10-4

10-3

10-2-2 10-1-1 10 10 Average Path Blocking Probability

Evolution of Optical Packet-Switched Networks Capacity

Stage 3

Stage 2

Stage 1 Point-toPoint WDM (P2P)

Optical Burst Switching (OBS)

Optical Packet Switching (OPS)

Optical Circuit Switching (OCS)

Time

Optical Packet-Switched Network The “Holy Grail” of Optical Networking

Optical Packet Switches With Buffering

OXC

Access Router

• Will a viable optical buffering technology emerge? • Can OPS reduce energy consumption?

Optical Packet Switch (OPS)

Forwarding Engine

Electronics

Optics

1

1

1

F Demutiplexers

K

WavelengthInterchanging Cross Connect + Header Replacement

F

Output Buffers

Input Synchronizers

2

1

Mutiplexers

Optical Buffer Structures Control

Delay Line

Delay

Variable Delay Line

Delay

Recirculating Loop

Cross Point

Staggered Delay Line

Delay

Cross Point

Delay

Cross Point

Optical Fiber Buffers Total buffer capacity of 104 Gigabits ~ 103 RAM chips Cost < US$ 50k Buffer power dissipation < 1 kW Cisco CRS-1 with 1000 ports, 250 ms buffering per port

Total fibre length = 40 Gm 150 times distance from Earth to Moon! .

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

Reduced Buffer Size Minimum feasible buffer size?

~5 μs (~20 packets) buffering per port

Optical fiber delay lines

Total fibre length = 1000 km Loss per port = 0.2 dB

Planar waveguide or slow light delay lines (0.1 dB/cm)

Loss per port = 33,000 dB Loss Tucker, PS 2007

Energy

Holographic Buffers Holographic Medium: Photorefractive material (e.g LiNbO3, polymers) Output image Write speeds up to 1 Gb/s Read speeds up to 10 Gb/s Reference beam Input image

Orlov et al., Proc IEEE, 2004 Psaltis, CLEO 2002 Ashley et al. IBM J. Res. Dev., May 2000

Storage density

Retention time

Access Time

Write Time

1/λ3



~ 50 μs

> 500 μs

Comparison of Optical Buffer Technologies Technology

Fiber

Planar WG, Slow Light

Optical Resonator

Holographic

CMOS

Access Time

Structuredependent

Structuredependent

Small

~ 50 μs

200 ps

Retention Time

> 500 μs

< 5 μs

1-100 ns



64 ms

Capacity (Packets)

> 2,000

< 20

100 pJ/bit (10 pJ/bit per gate)

Benes Array

Tucker, JLT 2005, OSN 2008

Benes

Chips (2 pJ/bit)

Observations on Optical Packet Switching •

No viable optical buffering technology in sight



Optical switch fabrics may become competitive with CMOS



Not clear whether optical packet switching will solve the energy bottleneck problem

Summary •

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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