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

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

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

4. Page 4 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 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 rise 1 100BASE-TX ~ 500 mW 1000BASE-T ~ 1100 mW 10GBASE-T ~ 10,000 mW 2 –Could we save energy by reducing energy-use during idle periods? 1 http://www.ieee802.org/3/az/public/jan08/hays_01_0108.pdfhttp://www.ieee802.org/3/az/public/jan08/hays_01_0108.pdf 2 http://www.ieee802.org/3/eee_study/public/mar07/kohl_01_0307.pdfhttp://www.ieee802.org/3/eee_study/public/mar07/kohl_01_0307.pdf

5. Page 5 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 5 Rationale From the Call For Interest presentation

6. Page 6 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 6 Rationale From the Call For Interest presentation

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

8. Page 8 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 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 Interface PCS – Physical Coding Sublayer PMA – Physical Medium Attachement PHY – Physical Layer Device

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

10. Page 10 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 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 Data/ IDLE Refresh Wake Sleep DATA/ IDLE Low-PowerActive TqTr Tw_PHY Ts Assert LPI Deassert LPI IDLE Wait a minimum of Tw_Sys before sending data (Tw_sys >= Tw_PHY) Tw_sys Hold 1 EEE: The new networking protocol for saving watts, datacenterdynamics.com, September 20, 2010

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

12. Page 12 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 12 A system view (switch centric) http://www.ieee802.org/3/az/public/may08/dove_02_05_08.pdf

13. Page 13 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 13 Opportunities for Innovation Areas to explore –Improvement of efficiency –How to minimize latency variation –Development of control policies –Integration with Network Management –

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

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

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

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

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

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

20. Page 20 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 20 Thank You!

21. Page 21 IEEE P802.3 Maintenance report – July 2008 Plenary Version 1.0 Joint Techs 31 January 2011Page 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.htmlhttp://ieee802.org/3/az/index.html http://www.energystar.gov/ia/partners/prod_development/new_specs/downl oads/small_network_equip/SNE_Draft_Framework_V1_0.pdfhttp://www.energystar.gov/ia/partners/prod_development/new_specs/downl oads/small_network_equip/SNE_Draft_Framework_V1_0.pdf