Did you know that in 2005 alone, all the network controllers (in computers, switches, routers, etc.) in the United States consumed 5.3 terawatt-hours of energy, sufficient to keep 6 billion 100-watt lightbulbs shining for a full year? As the May issue of IEEE Spectrum reports, a major reason for this is that network controllers maintain the same appetite for energy regardless of whether they are not in use or in full throttle operation. This is incredibly wasteful, since people only use their links at full throttle for 5% of the time on average, studies have shown.
There are currently two competing schemes that aim to address this problem in the near future:
- Adaptive Link Rate, developed by researchers from USF Tampa and Lawrence Berkeley National Laboratories, which will step down the speed of an Ethernet link if the full capacity is not needed. The researchers, Ken Christensen and Bruce Norman, claim that simply switching between 100Mb/s and 1Gb/s (in home, office and data-center devices) whenever possible will already save $300m in energy costs. The problem facing their solution is that it currently takes 2 seconds to step down the speed of an Ethernet link (the link has to be dropped and reinstated), which is unacceptable. A faster protocol for linking will be needed, and the pragmatic requirement is set at 1 millisecond.
- “Low-power idle”, proposed by Intel, in which the controller will always operate at the maximum rate, but will be put into a sleeping state when not in use. Intel claims that this will provide better results. Once again, turning the device on and off is a challenge, but up to 1Gb/s, it is easier than switching speeds. When it comes to 10Gb/s, however, there is no clarity as to which scheme is desirable.
Whereas the call has not been made yet, “a complete redesign of the network interface controller system is needed”, Cisco’s Hugh Barass is quoted as confirming.
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