Lecture: 7 Energy Efficiency in Optical Networks

Ajmal Muhammad, Robert ForchheimerInformation Coding Group

ISY Department

Outline

Introduction to Energy Issue Network Device’s Power Profile

Access, metro & core networks Approaches to low Energy Networking Energy Saving Strategies Core, metro & access networks

MotivationTwo main factors that drive the quest for “Green” networking(1) Reduction of CO2 emission

The ICT (Information and Communications Technology) sector is responsible for 2.0% of the global greenhouse emissions, estimated by ITU (International Telecommunication Union).

(2) Reduction of operational costPower consumption of the ICT (Information and Communications Technology) accounted for the 4% of the global energy consumption

BAU: Business-As-UsualECO: Eco Sustainable

For European Telecom network infrastructures

• 50 % of CO2 emission is due to the

production stage• 45% due to the usage stage• 5% due to recycling/disposal stage

Terminal versus Network Power Consumption

Typical current mobile terminal power consumption is 0.83Wh per day (including battery charger and terminal).

The corresponding network power consumption is 120Wh.

The ratio is 150:1 and therefore the network power consumption is the main contributor to CO2 and effort has to be directed at the network primarily.

Significant research effort has gone into extending the mobile terminal battery life by optimizing and reducing its power utilization from 32Wh per day in 1990 to 0.83Wh per day in 2008, a factor of 38.

In comparison the network power consumption has received little attention to date.

Power Consumption of Access Networks

Mobile access is becoming dominant access technology Any where, any time, any service

Mobile is least energy efficient~25 W/user @ 10 Mb/s

PON is most efficient~7 W/user

PON: Passive optical NetworkHFC: Hybrid fiber coaxialPtP: Point to pointFTTN: Fiber to the node or neighborhood

Network Segmentation

Key Components

• Customer home terminal ADSL modem, ONU….• Access network field equipment PON splitter, DSLAM, RF amps…• Central office equipment OLT, gateway, switch, base station,…

Access Network

Metro Network

Key Components: Core Network• Core routers & switched• Number of router hops• Long haul & submarine optical WDM transport• EDFAs, Raman Amps, transmit & receive units, etc.• TDM and WDM cross connects & OADM

Photonic Versus Electronic Switching

Photonic switching has much lower energy consumption compared to electronic switching.

It has been shown that the power needed per bit for switching is 100 to 1000 times higher in an electronic semiconductor switch as compared to a photonic switch.

Data Centers and Content Servers

Access, Metro, Core Power ConsumptionPON based access network - power consumption estimates are 10W for optical network units (ONU) and 100W for optical line terminal (OLT) which resides in an edge node.

Edge router in the metro, for example Cisco 12816, with capacity 160Gb/s consumes 4.21 kW. Efficiency= 26.5nJ/bit

Core router, such as Cisco CRS-1 with 640 Gb/s capacity consumes 1020 kW. Efficiency= 17nJ/bit

WDM systems connecting the edge nodes to the core node consume 1.5 kW for every 64 wavelengths.

Typically one multi-wavelength amplifier is required per fibre, consuming around 6W.

The WDM terminal systems connecting core nodes consume 811 W for every 176 channels, while each intermediate line amplifier consumes 622 W for every 176 channels.

Router Power ConsumptionDominated by router forwarding engines

Power driver: IP look-up/forward engine

I/O- optical transport: is lower in powerConsumption than switch fabric

Outline

Introduction to Energy Issue Network Devices Power Profiles

Access, metro, core network components

Approaches to Low Energy Networking Energy Saving Strategies Core, metro, access networks

Approaches to low Energy Networking

1

2

3

Introduce and design: 1)More energy efficient elements for network devices2)Optimize the internal organization of devices3)Reduce devices intrinsic complexity levels

Modulate capacities of processing engines and of network interfaces, to meet actual traffic loads and requirements

Smartly and selectively drive unused network/device portions to low standby mode

Network Domain Utilization

Internet traffic profile

Networks are provisioned withresources for worse case scenario

Energy Saving in Core Networks

Approaches

Selectively turn down network elements

- Energy efficient protocols

Energy efficient network architectureEnergy efficient routing Green routing

Energy Efficient Protocols

Sleep & standby states Network devices enter low power state when not in use

Can apply to systems and sub-systems Need to ensure network presence is retained use network connection proxy with sleep protocol

Need to account for state transition energy and time

May have multiple lower energy states

IEEE Energy Efficient Ethernet (802.3az) Low power idle mode when no packets are being sent Approved Sept. 2010 Currently applies to copper interface only; not optical

Example: Exploiting Sleep Mode

must be active to support working lightpath

can be set to sleep

off: not used

Dynamic Rate Adaptation

Modify capacity of network devices in response to traffic demands

Change clock frequency, processor voltage

Power = C x Voltage2 frequency

Slower speed to reduce power consumption

100 Mb/s uses 10-20 W less than 10GE, 4 W less than 1GE

Need to allow transition time between rates

Dynamic rate adaptation and standby states can be combined

Sleep Mode for Dynamic NetworksSome nodes are selected to go to sleep according to the traffic flow and their location in the network topology

When nodes go to sleep, they can still transmit and receive traffic but they cannot route traffic

A node which is the only neighbour for another nodecannot go to sleep

Some traffic flows will have to take longer routes, i.e., energy is saved at the expense of QoS

If the network blocking probabilityexceeds the acceptable (service)blocking probability threshold, themost recent node to sleep wake up

Energy Efficient Network Architecture

Architectures that reduce the number of router hops Optical bypass

Layer 2 rather than Layer 3 where possible

Without optical bypass:All traffic goes to IP layer for processing~10nJ per bitAllow aggregation of incoming traffic flowStatistical multiplexing

Layer 3

Layer 2

Architecture: Bypass Option

With bypass:

TDM Layer Some traffic streams processed at TDM layer

~ 1nJ per bit

WDM Layer

Some traffic streams processed at WDM layer

< ~ 0.1nJ per bit

Switching wavelengths

Energy Efficient RoutingNetwork with Dedicated Path Protection

Energy-unaware Routing Energy-aware Routing

Energy Efficient RoutingNetwork with Shared Path Protection

Energy-unaware Routing Energy-aware Routing

Green Routing

Energy Saving in Metro Networks

Reduce Regeneration

PIC: Peripheral Interface Controller

WSS: Wavelength Selective Switch

ROADM: Reconfigurable Optical Add Drop Multiplexer

Energy Efficient Traffic Grooming

DXC: Digital cross-connect

OXC: Optical cross-connect

FG: First Generation

SH: Single-hop

MH: Multi-hop

Energy Efficiency in Access Networks Remove Layers

Network simplification

Today

IP

ATM

PSTN

DPCN

PDH

SDH - mesh

SDH - MSH

IP

ATM

PSTN

DPCN

PDH

SDH - mesh

SDH - MSH

DSL

KiloStream

PSTN

Fibre

Copper

DWSS

21CN

IP/MPLSFibre &Copper

Copper

MSAN

Call Control

Content

WWW

ISP

Multi - service access Converged core

Current thinking. No implementation assurances

Wireless

Ethernet Backhaul

Other CPs

I/connects

British Telecom network architecture today

More power

Less power

Future Plan

From PON to Long Reach-PON

The Ring-and-Spur LR-PON

Two dimensional coverage for failure protection

Reusing the existing metro rings

Cost-effective extended coverage integrated system less active sites low CapEx and OpEx