Graduation Year


Document Type




Degree Granting Department

Computer Science and Engineering

Major Professor

Kenneth J. Christensen, Ph.D.

Co-Major Professor

Miguel Labrador, Ph.D.

Committee Member

Jarred A. Ligatti, Ph.D.


Green networks, power consumption, performance evaluation, simulation, Packet Coalescing, adaptive shutdown, local area networks, LAN switches


It is estimated that networked devices consumed about 150 TWh of electricity in 2006 in the

U.S. which has cost around $15 billion and contributed about 225 billion lbs of CO 2


greenhouse gas emissions. About 13.5% of this energy is consumed by network equipment such

as switches and routers.

This thesis addresses the energy consumption of Ethernet, and designs and evaluates

improvements on existing methods to reduce the energy consumption of Ethernet links and


Energy Efficient Ethernet (EEE) is an emerging IEEE 802.3 standard which allows Ethernet

links to sleep when idle. In this thesis, a performance evaluation of EEE is completed. This

evaluation replicates previous work by Reviriego et al. in an independent manner. The

performance evaluation shows that EEE overhead results in less energy savings than expected. A

new method based on Packet Coalescing is developed and evaluated to improve the energy

efficiency of EEE. Packet Coalescing bursts packets such that EEE overhead is minimized. The

results show that EEE with Packet Coalescing for 10 Gb/s Ethernet can achieve very close to

ideal (or energy proportional) performance at the expense of an insignificant added per

packet delay.

Periodically Paused Switched Ethernet (PPSE) was previously proposed and prototyped by

Blanquicet and Christensen in 2008. PPSE uses periodically sent notification packets to halt

packet transmission into a LAN Switch and thus allowing the switch to sleep periodically. In this

thesis, a first performance evaluation of PPSE is completed. The evaluation in this thesis shows

that a PPSE for 10 Gb/s Ethernet LAN Switches achieves either significant energy savings at the

expense of an excessive packet delay, or less than expected savings with a less than human

response time added per-packet delay. An improvement to PPSE (Adaptive PPSE) is proposed

and developed based on an adaptive policy. The adaptive policy considers past traffic load to

determine whether to put the switch to sleep or not. The evaluation shows that Adaptive PPSE

can achieve very close to ideal performance at the expense of an added average per packet delay

which is less than half of the human response time.