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«Insomnia in the Access ». Marco Canini EPFL. Or How to Curb Access Network Related Energy Consumption. Joint work with.
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«Insomnia in the Access» Marco CaniniEPFL Or How to Curb Access Network Related Energy Consumption Joint work with Eduard Goma, Alberto Lopez Toledo, Nikolaos Laoutaris (Telefonica Research), Dejan Kostić (EPFL), Pablo Rodriguez (Telefonica Research),RadeStanojević(IMDEA Networks), Pablo YagüeValentín(Telefonica Research)
Greening the ICT ? Datacenters PCs &peripherals Backbone Access network
Energy consumption of telcos 2.1 TWh 4.5 TWh 3.7 TWh 9.9 TWh
Access dominates energy consumption Backbone/Metro/Transport ACCESS
A typical DSL access network ACCESS ISP PART USER PART METRO CORE Gateway
A typical DSL access network ACCESS ISP PART USER PART METRO CORE Gateway Cable bundle DSL Access Multiplexers(DSLAMs) Central Office
Can we save energy? How? Challenges in greening the access Two practical techniques can save of the access energy … With a performance bonus
Individually, they do not consume a lot #1: Huge number of devices But collectively … 2 orders of magnitude more gateways than DSLAMs 1 order of magnitude moreDSLAMs than metro devices 2 orders of magnitude moreDSLAMs than backbone devices PhotoBlackburn
2#: High per bit energy consumption Backbone/Metro ACCESS 010 101101001001 010 101101001001 At full load, access devices 2-3 orders of magnitude higher than metro/backbone
Energy proportionality? 100% 70%
3#: Utilization < 10% Already bad here … but most of the time here
Sleeping saves energy ZZZ Sleep-on-Idle (SoI)Devices enter sleep mode upon periods of inactivity
SoI fails in access networks ACCESS ISP PART USER PART METRO An ADSL line needs 1 minute to wake up… but cannot enjoy a minute’s sleep
What if we can put 80% of gateways to sleep? 100 W 15 W ZZZ 1 W per modem Save big fraction at the user side ISPs … not so much
Line cards very unlikely to sleep by SoI Line cards Modem on Modem off Static assignment of lines to DSLAM ports is a problem DSLAM
OUR APPROACH • Greening the user part: aggregation • Greening the ISP part: line switching
Greening the user part – Aggregation ? Broadband Hitch-Hiking (BH2) Threshold-based heuristic algorithm: direct traffic to neighbor gateways during light traffic conditions ? ? ? On average 5-6 WiFi networks overlap in typical urban settings
Broadband Hitch-Hiking(BH2) ZZZ 20% 15 W ZZZ ZZZ 5% 5% 0% 35% 30% 30% 45% 50% 25% Load on home gateway is low direct light traffic to a neighbor gateway and let home gateway sleep Load on neighbor gateway is high go back to home gateway Load on neighbor gateway is low look for another neighbor or go back to home gateway
BH2 under the hood • Gateways assumed to have: • SoI • Ability to wake on traffic • BH2 terminals use WiFi card virtualization:[Giustinianoet al., MobiCom ’10; Kandulaet al., NSDI ’08] • Estimate load on all gateways in range • Maintain connectivity with 1 or few backup gateways Only modify the terminal wireless card driver
Greening the ISP part – Line switching Line cards Switching is for lines, not for packets DSLAM 40-way switch AT&T operators connecting transatlantic calls at the international switchboard in New York, circa 1930. (www.corp.att.com) Full switching maximizes savings …but cost quickly grows with the number of ways
Small 4-way switches are enough 4-way switches Line cards DSLAM Put line cards to sleep Each k-switch packs active lines to the top Simple micro-electro-mechanical switches with near-zero power consumption
Evaluation • Traces: CRAWDAD UCSD – 272 clients, 40 gateways • Scenario: 4 x 12-port line cards; 5.6 avg. gateways • Results for 4 schemes • Baseline: no sleep • Gateways, modems, line cards don’t sleep • Each terminal only connects to its home gateway
How many gateways can sleep? Peak hours Scheme 1: SoIfor gateways, modems & line cards
How many gateways can sleep? BH2 puts to sleep 70-90% of gateways Scheme 2: BH2 + k-switchBH2every 150 s + 12 x 4-switches
How many gateways can sleep? Scheme 3: OptimalBest clients to gateways assignment + full switch
What is the impact of gateway density? Just home + 2 neighbors 50%+ of gateways sleep
How much energy can we save? BH2 + k-switch saves 66% Optimal savings are 80%
What are the savings for the ISP? Scheme 4: SoI+ k-switchCombine switching with SoI
What are the savings for the ISP? Savings come from both aggregation and switching
What are the savings for the ISP? Savings come from both aggregation and switching
Prototypedeployment + 1st floor 2nd floor 3rd floor Limitation: home gateway + 2 neighbor gateways per client
Considerations for deployment Security Privacy Incentives
A performance bonus Bonus: reduced crosstalk Powering off lines makes the remaining … go faster due to reduced crosstalk!
Conclusions • 80% energy can be saved at the access • Aggregation + switching save 66% of energy • Surprising result: turning DSL modems off increases the performance of remaining modems • Applying our solution to all DSL users worldwide, yields savings of 33 TWh per year • ½ of energy going into US datacenters Thank you!Questions? • Or the output of3 nuclear power plants