This paper examines the energy wasted by computers not taking advantage of idle times to go into lower power sleep modes. The authors straight out acknowledge that this problem of when and how to effectively put nodes to sleep without them losing their network presence has been examined, with wake-on-LAN and proxying as potential solutions.
Based on traces from actual users, they justify the need for these solutions by showing that the studied computers actually do spend a lot of time in idle and that in many cases, long gaps of time pass between packet arrivals at the idle machine. Not suprisingly, the machines tend to have more frequently arriving packets in the office setting than in the home setting, with some users having even more available idle time than others.
I like this paper because it breaks down the type of network traffic seen in both the home and office settings; it starts out breaking both the incoming and outing packets into unicast, multicast, and broadcast groupings, and then further examines the breakdown of the multicast and broadcast packets into such things as ARP, IGMP, etc. These breakdowns are important because the power savings possible due to proxying for a node are dependent on which packets a node does not actually need to be woken up for.
Protocols are classified into groupings such as "don't-ignore" (ARP or DHCP requests for the sleeping node), "don't wake", ignorable, and mechanical response that the proxy can respond to. With these classifications in mind, the authors present 4 proxy schemes that offer varying levels of power savings, with the tradeoff that less application state is maintained. They find that their more aggressive schemes offer a lot of power savings, particularly in the office environment, and create a prototype of their proxy architecture in Click.
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