Energy Efficient Networks

Communications is another area where we pay an energy/heat/carbon price for speed. IEEE Spectrum reported in 2008 that network interface controllers in computers and switching gear consume over 5 terawatt-hours per year in the United States alone. 1/Gb/s links consume 4W more than their 100 Mb/s counterparts and the upcoming 10 Gb/s link could consume 10-20W more. Fortunately, energy-efficient networking is receiving more attention as Green ICT expands beyond the data center.

Automatically turning links on/off and switching between bit rates are two potential ways of managing power consumption being examined by the IEEE P802.3az Energy Efficient Ethernet task force. A related initiative is the Energy Efficient Internet project. In the meantime, judicious specing of link performance requirements will help hold down power consumption and heat/carbon generation.

Our attention to the "C" in Green ICT generated some contributions from Ken Christensen of the Energy Efficient Internet Project.

He called my attention to the paper The Greening of the Internet, in which the authors write "Putting interfaces on switches or routers to sleep can have serious side-effects because of the manner in which various protocols work." They go on to describe network "behavior [that] is clearly unnecessary and expensive" generated by putting devices to sleep. The authors are ultimately positive about the energy-saving benefits: "It appears that sleeping is indeed a feasible strategy but it will require some changes to the current protocol specifications. Further, in order to maximize the amount of energy conservation, we note that some modifications to the Internet architecture may be needed..." My take-away is that well-intentioned but poorly-considered implementations could cause more network-wide power consumption and bandwidth utilization than is saved at the individual device level.

What I found most telling is Christensen's own observation that "Most ICT energy use and waste is in user end systems...Not data centers...Not Internet core".

Update 2010.06.22
Networking gear can impact a computer's green rating. Apple's Mac Pro appears to be an EPEAT Gold product in all configurations, for example, until one looks at the EPEAT registry Exceptions field, which notes "Systems configured with the optional Apple Fibre Channel or Mac Pro RAID Card are not included under this EPEAT registration."

Update 2010.06.30
The European Research Consortium for Informatics and Mathematics' October 2009 issue of ERCIM News has articles about energy-efficient networking.

Update 2011.12.01
Climate Savers Computing Initiative (CSCI) launched a focus on reducing network energy consumption. This includes "three CSCI white papers produced to help organizations design, specify and manage networks that are optimized for energy efficiency."

Click on the "comm" tag above for more in the "C" in Green ICT.