Lecture: 7 Energy Efficiency in Optical Networks
Ajmal Muhammad, Robert Forchheimer
Information 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
Motivation
Two main factors that drive the quest for “Green” networking
(1)
Reduction of CO2
emission
(2)
operational
cost
PowerICT
consumption
of the
ICTCommunications
(Information and Communications
The
(Information
and
Technology) sector is
Technology)for
accounted
4% greenhouse
of the globalemissions,
energy consumption
responsible
2.0% of for
thethe
global
estimated by
ITU (International Telecommunication Union).
BAU: Business-As-Usual
ECO: Eco Sustainable
•
•
•
50 % of CO2 emission is due to the
production stage
45% due to the usage stage
5% due to recycling/disposal stage
For European Telecom network infrastructures
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 Network
HFC: Hybrid fiber coaxial
PtP: Point to point
FTTN: 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 Consumption
PON 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 Consumption
Dominated by router forwarding engines
Power driver: IP look-up/forward engine
I/O- optical transport: is lower in power
Consumption 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
Modulate and
capacities
of processing engines and of
Introduce
design:
Smartly interfaces,
and selectively
drive
unused
network
to
meet
actual
traffic
loads devices
and
1)network/device
More energy efficient
elements
for
network
portions to low standby mode
requirements
2) Optimize the internal organization of devices
3) Reduce devices intrinsic complexity levels
1
2
3
Network Domain Utilization
Internet traffic profile
Networks are provisioned with
resources for worse case scenario
Energy Saving in Core Networks
Approaches




Selectively turn down network elements
- Energy efficient protocols
Energy efficient network architecture
Energy 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.
Currently applies to copper interface only; not optical
2010
Example: Exploiting Sleep Mode
off: not
used
must be active to
support working
lightpath
can be set to
sleep
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 Networks
Some 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 node
cannot 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 probability
exceeds the acceptable (service)
blocking probability threshold, the
most 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
Layer 3
Layer 2
Without optical bypass:
All traffic goes to IP layer for processing
~10nJ per bit
Allow aggregation of incoming traffic flow
Statistical multiplexing
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 Routing
Network with Dedicated Path Protection
Energy-unaware Routing
Energy-aware Routing
Energy Efficient Routing
Network 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
PSTN
PSTN
Copper
British Telecom network architecture today
DPCN
KiloStream
More power
ATM
DSL
IP
Fibre
SDH
- MSH
SDH
SDH - mesh
- mesh
DWSS
PDH
Today
Multi -service access
Converged core
Copper
Call Control
Ethernet Backhaul
Fibre &
Copper
WWW
IP/MPLS
MSAN
Content
ISP
I/connects
Wireless
Future Plan
Current thinking. No implementation assurances
Network simplification
21CN
Less power
Other CPs
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