POWER-AWARE NETWORK DESIGN

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29 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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POWER
-
AWARE
NETWORK DESIGN

«Power Awareness in Network Design and Routing»

J. Chabarek et al.

«Energy
-
Minimized Design for IP Over WDM Networks»
G. Shen, R. S. Tucker

Introduction


The Internet is expanding tremendously


Growth in the number of end users and connection speeds
-
>
exponential increase in bandwidth demand


Increase in energy consumption


Cost of transmission and switching one of the major
barriers


Energy consumption may become a barrier


1%
-

2% of total electricity consumption in US


A cut of 1% in the Internet energy consumption means about US$5 billion per
year


Increase in power density


Thermal issues
-
> limitations of air cooling


Increase in operational costs


Increase greenhouse footprint


Save the Earth!!!

Power Aware Design Areas (I)


Three main areas for power aware design


System Design


Development in CMOS technology
-
> improvements are slowing down


Multi
-
Chassis Systems: separate physical components clustered
forming a single logical router


Aggregate power consumption increases
-
> heat spread over a large physical area
-
>
existing cooling techniques used


Alternative Systems: optical switches


Terabits of bandwidth at much lower power dissipation


Protocols


Investigated in wireless networks
-
> Opportunities in wire
-
line networks


Basic notion: put components to sleep if low traffic load


R
outing protocols: routes calculated with power consumption
constraints

Power Aware Design Areas (
II)


Network Design


Deploy routers such that the aggregate power demand is minimized


Satisfying robustness and performance


Two approaches


Multiple router
-
level topologies satisfying capacity, robustness and power
consumption


Limit power
-
hungry systems to a subset of routers



Selection of chassis and line cards in routers is a main issue to reduce
power consumption



In IP over WDM networks


IP routers use more than 90% of total power


Lightpath bypass is used to reduce the number of IP router ports
-
> IP ports
consume major energy in IP routers

Router Power Consumption


Router power consumption depends on


Type of router chassis


Type and number of line cards deployed in the chassis


Configuration and operating conditions


Size of packets


100 bytes / 576 bytes / 1500 bytes


Size of forwarding table


1000 entries / 32000 entries


Type of traffic


UDP


TCP


Employed protocols and techniques


OSPF


Netflow


Unicast Reverse Path Forwarding (
uRPF
)


Access Control List (ACL)


Active Queue Management
-

Random Early Detection (AQM


RED)

Router Power
Consumption


Chassis and line card combinations


Chassis: Cisco GSR 12008 / Cisco 7507

Router Power
Consumption


Chassis and line card combinations (cont.)


Base system is the most consuming


7507 chassis + router processor
-
> 210 Watts


GSR chassis + router processor + switching fabric
-
> 430 Watts



It is best to minimize the number of chassis and maximize the
number of line cards per chassis



Calculated power consumption of different cards

Router Power
Consumption


Configuration and operating conditions


A 4
-
port Gigabit Ethernet line card and a OC
-
48 card in a GSR chassis
is used



Deployed
testbed
:







Router Power Consumption


Configuration and operating
conditions (cont.)


Constant bit rate UDP traffic and different packet sizes


1500
bytes / 576 bytes / 100 bytes









Power consumption increases as packets get smaller!!!


Router Power Consumption


Configuration and operating conditions (cont.)


Constant bit rate UDP
traffic, medium packets
and different
features


Large forwarding table / ACL /
uRPF

/ OSPF













uRPF

is the most consuming


Large forwarding table is less consuming!!


Router Power Consumption


Configuration and operating conditions (cont.)


Self
-
similar TCP traffic, 75% offered load
and different features


Netflow

/ AQM
-

RED








Power consumption similar to UDP with large
-
sized packets






Router Power Consumption


Configuration and operating conditions (cont.)


Maximum variation in previous slides
-
> 20 Watts


Extrapolating a fully loaded chassis
-
> 150
-

200 Watts


Less significant than chassis/line card configuration


General Model:




PC
-
> power consumption of router


X is a vector defining chassis type, line cards, configuration and traffic profile


CC
-
> power consumption of a chassis type


N
-
> number of line cards


TP
-
> scaling factor (traffic utilization)


LCC
-
> cost of line card

Power Consumption Optimization


Main focus: allocation of line cards and chassis in nodes
to minimize power consumption


Mixed
-
Integer resource allocation problem with
multicommodity

flow constraints


Inputs


Network with OSPF link weights


Traffic matrix


Line card and chassis options


Outputs


How each node should be provisioned


Multipath routing


Implemented with General Algebraic Modeling System
(GAMS)

Power Consumption Optimization


Networks are taken from the
Rocketfuel

project


Inferred weights and link latencies


Link weights
-
> calculate approximate bandwidths of each link


Traffic matrixes generated with a gravity model


Three additional random graphs with 12 nodes and varying number of
directed edges (Waxman method)

Power Consumption Optimization


Network design problem: deploy different chassis/line
card configurations such that provisioning requirements
are satisfied and power consumption in minimized


Traffic is scaled for each origin
-
destination pair
-
> linear scaling factor


Varies provisioning requirements


Traffic flows might be altered to put cards/chassis to sleep in low utilization



First scenario includes only GSR chassis and OC
-
48 line card


Only 10 line cards allowed per chassis


Scaling factor varies from 0.1 to 40



Power Consumption Optimization










Other experiments relaxing line cards per chassis, chassis type and
card types (not in the paper)


Minimum power consumption
-
> chassis accommodating large numbers
of line cards and line cards capacities that closely match demand


Power Consumption Optimization


Power savings


Compared to a non
-
power
-
aware network design (shortest path)


Using a specific chassis (GSR) and line cards (OC
-
48 or 0C
-
12)








OC
-
12 line cards achieve smaller savings
-
> more ingress/egress node
ports


Cost of additional connectivity is zero as long as the number of ports does not require
additional line cards

IP Over WDM Network


IP layer:


Core IP router aggregates data traffic from low
-
end access routers


IP router ports consume major energy (forwarding process)
-
> number of IP ports as
measure of total power consumption


Optical layer


Optical switches interconnected with physical fiber links


May contain multiple fibers


Each fiber needs a pair of multiplexer/demultiplexer


Each wavelength require a pair of transponders
-
> full wavelength conversion is
assumed


EDFA amplifiers are deployed on fiber links


IP Over WDM Network


Two implementation approaches



Lightpath non
-
bypass


All data carried by lightpaths is processed and forwarded by IP routers


All lightpaths incident to a node must be terminated



Lightpath bypass


IP traffic whose destination is not the intermediate node
-
> directly
bypasses the intermediate router


Saves IP router ports


Energy Consumption Optimization for IP
over WDM


Network design
problem: d
esign an energy
-
minimized IP
over WDM network


Serving all the traffic demands


With a limited maximal number of wavelengths in each fiber


With a limited maximal number of IP router ports at each node



Inputs


Physical topology
-
> N nodes and E links


Traffic demand matrix


Number of wavelength channels per fiber and capacity of each wavelength


Maximal number of IP router ports at each node


Energy consumption of router ports, transponders and EDFAs

Energy Consumption Optimization for IP
over WDM


The optimization problem is solved using a Mixed
-
Integer
Linear Programming (MILP) model including


Energy consumption of IP routers, EDFAs and transponders


Layout of EDFAs


Ports for aggregating data from low
-
end routers


MILP model minimizes also the number of network
components
-
> could be used for cost
-
minimized IP over
WDM network


The computational complexity is high


O(N
4
) variables and O(N
3
) constraints


Heuristics are needed for fast solution

Energy Consumption Optimization for IP
over
WDM
-

Heuristics


Heuristics


Direct Bypass: directly establish virtual links (lightpaths) whose capacity
is sufficient to accommodate all the traffic demands between each node
pair


Routing of lightpaths
-
> shortest path routing


Simple


Could lead to low capacity utilization



Multi
-
hop bypass: traffic demands between different node pairs could
share capacity on common lightpaths


Elongate lengths of some IP traffic flows


Fewer lightpaths
-
> fewer IP router ports

Energy Consumption Optimization for IP
over
WDM
-

Heuristics


Multi
-
hop bypass heuristic:

Energy Consumption Optimization for IP
over
WDM
-

Setup


Five study cases


Linear relaxation of the MILP model
-
> lower bound


MILP optimal design


Non
-
bypass
-
> upper bound


Direct bypass


Multi
-
hop bypass


Inputs



Traffic demand between
each pair node:


Uniform distribution
within a certain range
centered at an identical
average

Energy Consumption Optimization for IP
over WDM


Test Networks


Test networks

n6s8

NSFNET

USNET

Energy Consumption Optimization for IP
over WDM


Total Power Consumption

n6s8

NSFNET

USNET

Larger topology
-
>


higher power consumption,


heuristics closer to lower bound


Non bypass
-
> upper bound

LP relax.
-
> lower bound


Linear relationship between total
power consumption and total traffic
demand intensity

Energy Consumption Optimization for IP
over WDM


Power Consumption Saving

n6s8

NSFNET

USNET

Larger topology
-
> higher savings,


longer lightpaths bypassing more


nodes
-
> fewer IP ports


Multi
-
hop bypass heuristic performs
better than direct bypass
-
>


Small traffic flows are aggregated

Energy Consumption Optimization for IP
over WDM


Component Consumption

n6s8

NSFNET

Energy Consumption Optimization for IP
over WDM


Geographical Distribution

n6s8

NSFNET

All bypass design have a more uniform power distribution


Solve problems associated with:


Supplying large amounts of energy


Removing associated heat

Energy Consumption Optimization for IP
over WDM


Cost Analysis


The model could be used for minimizing cost


Changing the optimization weights from energy to cost


May NOT be valid if components with low energy consumption are the
most expensive ones

N6s8 network based on the
MILP optimization model

Conclusions


Energy consumption may become a barrier for the
Internet


Operational costs


Greenhouse footprint


Cooling issues


Supplying large amounts of energy


Power aware design could solve it


Power aware system design


Power aware protocols


Power aware network design


Power aware network design could achieve important
savings


In IP over WDM networks, lightpath bypass could save power
consumption

References


[CHA08] J. Chabarek et al., «Power Awareness in
Network Design and Routing», Proc. Of IEEE INFOCOM,
2008


[SHE09] G. Shen, R. S. Tucker, «Energy
-
Minimized
Design for IP Over WDM Networks», Journal of Optical
Communication Networks, June 2009.