page 1 joint techs 31 january 2011 green ethernet winter 2011 escc/internet2 joint techs michael j....
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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