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Up to 300 Megawatt Worth of Keepalive Messages to be Saved by IPv6?

The Time Square Ball bringing in 2008 had more than 9,500 LED bulbs displaying 16 million colours while consuming power equivalent to about ten toasters. This compares to 600 incandescent and halogen bulbs adorning last year’s Ball.

Easy to forget that most mobile devices used by Time Square revelers were behind IPv4 NAT’s and that always on applications such as Instant Messaging, Push e-mail, VoIP or location based services tend to be electricity guzzlers. It so happens that applications that we want always to be reachable have to keep sending periodic keepalive messages to keep the NAT state active. Why is that so? The NAT has an inactivity timer whereby, if no data is sent from your mobile for a certain time interval, the public port will be assigned to another device.

You cannot blame the NAT for this inconvenience, after all, its role in live is to redistribute the same public addresses over and over; if it detects you stopped using the connection for a little while, too bad, you lose the routable address and it goes to someone else. And when a next burst of data communication comes, guess what? It doesn’t find you anymore. Just think of a situation we would loose our cell phone number every time it is not in use and get a new one reassigned each time.

Luckily there’s a way around but it requires a constant stream of keepalive message sent at preset intervals, often 30 second or so. These dummy messages give the NAT the illusion that the communication is still on and it doesn’t disturb your address. Only drawback is that this happens to drain the battery and shorten standby time considerably. Just try leaving IM off instead of on to see the difference.

How much could this possibly drain the battery? In their excellent study [PDF], Nokia’s Haverinen, Siren and Eronen tackled the issue. In a 3G environment, 20 second interval keepalive messages result in an average current of 34mA and this goes down to 6.1mA if no keepalive messages sent. If we know consider a Lithium Ion battery which is 3.6V and remember that Volt times Ampere gives Watts, this looks like 100.44 milliwatt saved. Imagine 3 billion 3G phones in 5 years time or so and bingo, roughly 300 megawatt of useless keepalive message. If we assume that all 3 billion 3G phones would be in use two hours a day on average, this still leaves 275 megawatt wasted.

How many power plants does it take to generate 300megawatt?
How many tons of carbon dioxide in the atmosphere to produce 300 megawatt?

An article in EE Times Europe estimated that mobile networks consume 61 billion kwh and that this could double by 2011. Do cell phones in standby draw less power from the base station than if they communicate all he time? A higher density of phones per cell site conceivable if inactive phones in standby instead of a quasi permanent state of excitement? Who knows, this could maybe save some additional megawatts, this time by the operator.

And while on the power topic, all of us running major networks or content server farms take note of their electricity bills. Jonathan Koomey of National Livermore Laboratories estimates in his study [PDF] that servers worldwide consumed a cool 123 billion kwh in 2005 for a total electricity bill of 7.2 billion dollar!

Did anyone recently voice the opinion that IPv6 and energy saving was just marketing hype? The Time Square Ball LED light bulb initiative sure must have had its detractors too.

Happy New Year!

Any opinions, findings, conclusions or recommendations expressed in these articles are solely those of the author and are not in any way attributable to nor reflect any existing or planned official policy or position of his employer in respect thereto.

By Yves Poppe, Director, Business Development IP Strategy at Tata Communications

(Any opinions, findings, conclusions or recommendations expressed in these articles are solely those of the author and are not in any way attributable to nor reflect any existing or planned official policy or position of his employer in respect thereto.)

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The Famous Brett Watson  –  Jan 8, 2008 12:53 AM

But does IPv6 result in reduced power consumption, particularly in light of its substantially increased header size? Think of all those extra bytes in every single packet, and all the energy they consume. IPv6 might cause the ice caps to melt! Save the planet from IPv6!

Ian Peter  –  Jan 9, 2008 8:24 PM

Well… 300 megawatts is the output of one smallish windfarm, or the equivalent of 2 boeing 747s average consumption - even if your assumption that IPv6 totally replaces NATs is correct. (I don’t believe I will live to see the day..)

And what is the power consumption of dual stacking? It would be just as easy to writean “Ipv6 will destroy the planet” story or “ICANN meetings responsible for global warming” .

There is a lot of things the IT industry can and should be doing in the climate change area - Bill St Arnaud has done a lot of work on this and there is a summary I wrote here.

Let’s concentrate on some of the more meaningful actions - propping up the IPv6 deployment case with such a weak argument does no good for either Ipv6 or climate change.

Try relocating your server farm near a renewable energy resource ad save money a the same time!

Alessandro Vesely  –  Jan 10, 2008 7:51 AM

This article depicts IPv6 as the protocol of choice for new generation devices. Increased granularity and universal addressability may possibly deliver better routing and pay back for increased header size.

What leaves me wandering about the argument is an application’s point of view. Eliminating NAT’s keepalives only results in a power saving if the upper protocol does not need keepalives in turn. As newer CPUs are able to fit power consumption curves more tightly against useful processing cycles, the cost of a sleeping thread vanishes and we may expect newer parameter settings to allow longer expire timeouts for connections. An application may keep a connection open as long as it trusts that its peer has not crashed, thus reliability matters too. Eventually, doing things well may be the winning strategy.

Yves Poppe  –  Jan 14, 2008 5:35 PM

What does 300 megawatt represent: precious little or a hell of a lot?

300 megawatt can be generated by a smallish wind farm?

Even in Australia where the relative size of everything never ceases to amaze me it is doubtful.

Consider the UK. In December 2007 the rather windswept British Isles had 160 grid connected wind farms totalling 1910 turbines generating 2320.09 megawatt. Makes an average of 14 megawatt per farm or 1.215 megawatt per turbine.

The biggest turbine in use in the world today, rated at 6 megawatt, seems to be in Emden, Germany and was produced by Enercon.  With a hub height of 135 meter and overall height of 198 meters I am not sure the neighbours would be smiling.  And depending how windy it gets more than 50 of these mastodonts would be required to generate a steady 300 megawatt supply… a smallish windfarm?

Two Boeing 747’s consume 300 megawatt?

Probably close if one refers to power generated under maximum thrust at take-off. The only catch is that a 747 runs on four jet fuel powered engines, not on electricity.  The current world record holder in the race for battery powered fixed wing aircrafts is a Frenchman who,  last December 23th,  flew a small wood-and-fabric single-seater,  for 48 minutes covering 50 kilometers. It was equipped with a 25 kilowatt engine. Logical next step would be to cross the Channel and be the new Blériot exactly 100 years later!.

A battery powered 747 or a jetfuel driven handheld? There is power and power even if both can be expressed in Watt.

Writing this makes me look with even more respect at humble milliwatts. These zillions of ridiculous little keep alive messages could represent some meaningfull amounts of energy after all and allow that all important phone call or message to go through when needed. 


Ian Peter  –  Jan 15, 2008 9:21 PM

Well maybe not smallish, but here is a 300mw wind farm in Ireland http://www.electricityforum.com/news/jul03/ireland.html - and my 747 figures came from the venerable wikipedia. But let me admit to being no expert on watts and milliwatts and equivalents, certainly I’m not the person to debate those with, I was just trying to get some perspective here.

So there are two threads here - one is that there are things that ought to be done about greenhouse gas emissions around IT and internet and communications. Agreed - a UK study has suggested that 10% of greenhouse gases are from IT industry - roughly equivalent to the aviation industry! Some of the priority actions than can assist include turning off 10s of millions of government computers at night, greater virtual server utilisation, cloud computing architectures, relocation of server farms near renewable energy sources, etc. There is lots than can be done and should be done, a lot of it relatively easy.

But the other thread which I reacted to is a suggestion that IPv6 should be a priority action here for global warming purposes. The argument doesn’t cut for me, either the assumption that somehow IPv6 will replace all NATs, or the assumption this will result in substantial energy savings.

Alessandro Vesely  –  Jan 16, 2008 11:37 AM

Ian Peter writes:

IPv6 should be a priority action here for global warming purposes. [...] the assumption this will result in substantial energy savings.

I don’t think IPv6 needs to be a priority task or provide substantial savings. The comparison with the LED bulbs is significant, as they had neither of those qualification. IPv4 and IPv6 are both available, the question is why we choose one or the other when we set up a (new) network. There are still valid reasons to use high-power bulbs, but there are bright alternatives too.

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