As energy prices soar, and governments and organisations start to sweat over their carbon footprint, the energy consumption of the Internet is coming under scrutiny.
US academics and researchers from companies Intel and Microsoft are developing strategies to cut the consumption of computer-network hardware.
While most personal computers adjust how much energy they use depending on their workload, and shut down when unused, network hardware does not.
The servers, routers and other components of networks are designed to cope with much larger amounts of data than they do day-to-day, and use roughly the same amount of energy whether idle or busy.
But subtly tweaking the flow of network traffic to allow routers and servers to work less hard, or spend more time "sleeping" in a resting state could make dramatic savings.
Smooth operator
Sergiu Nedevschi of the University of California in Berkeley, US, and colleagues at Intel Research labs in Berkeley and Seattle, have worked out how to make energy savings of around 50%, by delaying data flowing into a network by just a few milliseconds.
That is long enough to smooth out bursts and lulls in the data flow, and allows network hardware run at a consistently lower speed. Alternatively, information can be grouped into fewer, larger bursts to let the hardware sleep between chunks.
With today's hardware, either strategy could save between 40 and 80% of the energy used by a network's hardware, according to the researchers' simulations.
Regional impact
Sleeping is more effective for networks that are used less, they found. Since activity usually slows down at night, "you could sleep at night, and use rate adjustment in the day," Nedevschi says.
That approach is practical, but would not put a big dent in energy use in the US, because "routers and switches consume a very tiny amount of the annual energy here," says Suresh Singh of Portland State University in Oregon, US.
"However, the impact could be significant in developing countries like India," Singh adds, where networks are growing and electricity supplies are tight.
All-night gaming
Meanwhile, researchers at Microsoft Research in Redmond, US, are studying how internet servers use energy. If used for activities like instant messaging or online games they must keep connections open for long periods – minutes, hours, and sometimes days. That prevents them entering sleep mode at any time.
"In an extreme case, a single connection can keep a server on," says study leader Jie Liu. "Studies have shown that a server can consume 60% of its peak power even when it is idle," he adds.
Companies usually spread active connections evenly across many servers, which helps them handle surges in demand. But taking the opposite approach can save a lot of energy, Liu and colleagues found.
In an approach they call "load skewing," new connections are first sent to servers that are already busy. "The benefit is that it automatically creates servers that bear low load," Liu says. "These are the candidates for shutting down when the total load is low."
Real-life savings
In a 45-day real-world test on Microsoft's chat system, Windows Live Messenger, they found that this strategy allowed them to often shut down many servers, cutting energy use by about 30%.
Liu and colleagues "succeeded in significantly reducing power without any perceived effect in user experience," says Diana Marculescu of Carnegie Mellon University in Pittsburgh, US. Little attention has been paid to trying to balance these two factors, she adds.
Both the Nedevschi /Intel and the Microsoft research projects were presented in papers at the USENIX Networked Systems Design and Implementation conference
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