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Page 1 Joint Techs 31 January 2011 Green Ethernet Winter 2011 ESCC/Internet2 Joint Techs Michael J. Bennett Lawrence Berkeley National Laboratory

Page 1 Joint Techs 31 January 2011 Green Ethernet Winter 2011 ESCC/Internet2 Joint Techs Michael J. Bennett Lawrence Berkeley National Laboratory

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Page 1Joint Techs 31 January 2011

Green Ethernet

Winter 2011 ESCC/Internet2 Joint Techs

Michael J. BennettLawrence Berkeley National Laboratory

Page 2IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 2

These are my personal views

• Per IEEE-SA Standards Board Operations Manual, January 2005:– “At lectures, symposia, seminars, or educational

courses, an individual presenting information on IEEE standards shall make it clear that his or her views should be considered the personal views of that individual rather than the formal position, explanation, or interpretation of the IEEE.”

• The views expressed in this presentation are mine and not that of the IEEE

Page 3IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 3

Topics

• Overview of Energy-Efficient Ethernet (EEE)– Rationale

– What is EEE and where does it fit in the stack?

– Low Power Idle

– Optimizing Energy Efficiency

– Anticipated Benefits

• Opportunities for Innovation

• Possible future development of EEE

Page 4IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 4

Rationale

• Question about network energy-use began in 2005– Ethernet traffic is generally bursty

• Sample traffic analysis shows idle roughly 90% of the time

– Interface power on the rise1 • 100BASE-TX ~ 500 mW

• 1000BASE-T ~ 1100 mW

• 10GBASE-T ~ 10,000 mW2

– Could we save energy by reducing energy-use during idle periods?

1 http://www.ieee802.org/3/az/public/jan08/hays_01_0108.pdf2 http://www.ieee802.org/3/eee_study/public/mar07/kohl_01_0307.pdf

Page 5IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 5

Rationale• From the Call For Interest presentation

Page 6IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 6

Rationale• From the Call For Interest presentation

Page 7IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 7

What is Energy-efficient Ethernet?

• EEE is a method to reduce energy used by an Ethernet device during periods of low link utilization

• The premise for EEE is that Ethernet links have idle time and thus opportunity to save energy

• Specified for copper interfaces• “BASE-T’s’• Backplane

• The method we’re using is called Low Power Idle

Page 8IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 8

Where EEE Fits OSI Layers LAN CSMA/CD Layers

PHYSICAL

DATA LINK

NETWORK

TRANSPORT

SESSION

PRESENTATION

APPLICATION HIGHER LAYERS

Logical Link Control (LLC)

MAC Control (optional)

Media Access Control (MAC)RECONCILIATION

PCS

PMA

AUTO-NEGOTIATION

MEDIUM

PHY

xxMII

xxMII – Media Independent Interface MDI – Medium Dependent InterfacePCS – Physical Coding SublayerPMA – Physical Medium AttachementPHY – Physical Layer Device

Page 9IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 9

What is Low Power Idle?

• Concept: Transmit data as fast as possible, return to Low-Power Idle

• Saves energy by cycling between Active and Low Power Idle

–Power reduced by turning off unused circuits during LPI–Energy use scales with bandwidth utilization

Page 10IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 10

Low Power Idle Overview

• LPI – PHY powers down during idle periods• During power-down, maintain coefficients and sync to

allow rapid return to Active state• Wake times for the respective twisted-pair PHYs:

– 100BASE-TX: Tw_PHY <= 20.5 usec– 1000BASE-T: Tw_PHY <= 16.5 usec– 10GBASE-T: Tw_PHY < 8 usec

• Device energy consumption can be reduced by 80%1

Alert

Quiet Quiet Quiet

Data/

IDLE

Refre

sh

Refre

sh

Wake

Sleep

DATA/

IDLE

Low-PowerActive Active

Tq TrTw_PHY

Ts

Assert LPI Deassert LPI

IDLE

Wait a minimum of Tw_Sys before sending data (Tw_sys >= Tw_PHY)

Tw_sys

Hold

1EEE: The new networking protocol for saving watts, datacenterdynamics.com, September 20, 2010

Page 11IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 11

Optimizing Energy Efficiency

• Energy Efficiency can be optimized by using link-partner communications after the link is established

– Use Link Layer Discovery Protocol (LLDP) to change wake times.

– The longer the wake time, the longer the delay till frames can pass, i.e. latency variation increases

• Trade-off between energy savings and latency

• There are system power savings opportunities in addition to PHY power

Page 12IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 12

A system view (switch centric)

http://www.ieee802.org/3/az/public/may08/dove_02_05_08.pdf

Page 13IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 13

Opportunities for Innovation• Areas to explore

– Improvement of efficiency

– How to minimize latency variation

– Development of control policies

– Integration with Network Management

– <your idea goes here …>

Page 14IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 14

Opportunities for Innovation• A couple of examples:

– In October, 2009 Riviergo, et. al. published a paper examining the energy efficiency of P802.3az (Draft 1.2.1)

– They observed that the wake and sleep times are high compared to the time it takes to transmit a frame. The performance was analyzed using a variety of traffic profiles including traces from data centers

• The analysis suggested there could improvements in efficiency by buffering and bursting frames

Page 15IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 15

Opportunities for Innovation• Further work by Ken Christensen, et. al.

examines the trade-offs in performance of energy-efficient Ethernet– Builds from the work described in the previous

paper– Suggests a packet coalescence mechanism

can be used to further improve energy efficiency

• This kind of work is essential to the development of control policies to maximize energy savings

Page 16IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 16

Possible future developments• How do we continue the energy-efficiency effort

begun in IEEE802.3az-2010?– Participation in standards development

• Make sure energy is considered when evaluating possible new projects

– Encourage EPA to offer incentives network equipment• Energy Star for network equipment?

– Already working on “Small Network Equipment (SNE)”

– 802.3az referenced as Preliminary Features Under Consideration in Draft SNE Framework Specification

• Incentives are good for the market

Page 17IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 17

Possible future developments

• Optical Ethernet

–Optical PHYs were not studied during the study group phase of the EEE. The following need to be studied:

• Potential for energy savings

• Whether or not lasers can or should be cycled off (completely) and on

– Any adverse affects?

• Time to transition between states

Page 18IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 18

Possible future developments

• There may be opportunities to discover a better approach to achieving energy efficiency in new projects

• Impact of other technologies–How will virtualization/consolidation affect

traffic?–How will latency-sensitive applications work

with EEE?

Page 19IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 19

Summary• Energy-efficient Ethernet will save energy

–At the physical layer–In the system

• There are trade-offs for saving energy–Latency variation vs. energy use

• There are opportunities to develop the work done in P802.3az –Improvements in efficiency–Control policy and network management–Optical and higher speed Ethernet

Page 20IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 20

Thank You!

Page 21IEEE P802.3 Maintenance report – July 2008 PlenaryVersion 1.0 Joint Techs 31 January 2011 Page 21

References

• B. Nordman, Digital Networks: http://efficientnetworks.lbl.gov/enet.html

• K. Christensen, et.al., "IEEE 802.3az: The Road to Energy Efficient Ethernet," IEEE Communications, November 2010.

• W. Diab Use of LLDP, http://www.ieee802.org/3/az/public/jan09/diab_02_0109.pdf

• Dove, Energy Efficient Ethernet: A switching Perspective http://www.ieee802.org/3/az/public/may08/dove_02_05_08.pdf

• P. Reviriego, J.A. Hernandez, D. Larrabeiti, J. A. Maestro, IEEE COMMUNICATIONS LETTERS, VOL. 13, NO. 9, SEPTEMBER 2009

• P. Reviriego, et.al., Reduce latency in energy efficient Ethernet switches with early destination lookup, http://www.embeddedinternetdesign.com/design/224400698

• P802.3az public page, http://ieee802.org/3/az/index.html

• http://www.energystar.gov/ia/partners/prod_development/new_specs/downloads/small_network_equip/SNE_Draft_Framework_V1_0.pdf