Skilled in the Art of Being Idle: Reducing Energy Waste in Networked Systems

S. Nedevschi, J. Chandrashekar, J. Liu, B. Nordman, S. Ratnasamy, N. Taft, "Skilled in the Art of Being Idle: Reducing Energy Waste in Networked Systems," NSDI'09, (April 2009).

This paper argues that systems draw a lot of power even when they are idle which should obviously not be the case. Even though various solutions have been proposed over the years to save energy costs in clusters such as wake-on-lan (WoL) or proxies (NCP), there has been no in-depth evaluation of potential energy savings. In this paper, the authors proposed an extensible proxy architecture by analyzing a trace from 250 enterprise users (90% laptops and 10% desktops) at Intel Berkeley Research lab over 4 weeks consisting of common network protocol packets in the network. Their work was essentially a trace-driven evaluation of broader benefits and design tradeoffs  in desiging proxy architectures.

The evaluation of traces showed some really interesting results. On an average, desktops were idle >50% of the time wasting >60% of the energy. This scaled to 6 billion dollars being wasted per year (assuming 170 million desktop PCs in the US). Howeover, a strict wake-on-lan scheme that wakes a node on receiving any packet doesnt work well due to the fact that the incoming traffic is high even when the node is idle. To tackle this, a hybrid scheme is necessary that can proxy for certain protocol packets and wake the hosts for important packets that require user attention. The authors analyzed various such protocols and identified "key offenders" keeping volume of packets and half-time sleep as metrics for identifying them. Once these key offenders were identified, they can be ignored or responded by the proxy or the client can be woken up.

On idetifying various key offenders, the authors designed a general proxy architecture consisting of a set of rules of type (trigger, action). The trigger was based on incoming packet and proxy state while the actions could be drop, wake, respond or redirect. The system involved no modifications to the end systems and could be implemented as a separate network product which makes it extremely useful and easily deployable.