Thesis

LiteSwitch

LiteSwitch is a remote power management tool that controls the power states of machines via a web interface, relying on an agent that runs on the host machines and the Wake-on-LAN protocol. The aim is to reduce wasteful power consumption, thus lowering costs and carbon dioxide emissions. This paper details the project life-cycle in developing a first iteration of LiteSwitch including all core functionality. There are numerous additional features that could be added in future iterations. Some unexpected limitations to Wake-on-LAN were discovered. The reliable routing of magic packets across subnets is not possible given the default configuration of most routers. This is because magic packets are most readily addressed as subnet directed broadcasts, and due to a security threat known as a smurf attack, routers in their default configuration do not route subnet directed broadcasts.Various potential remedies and work-arounds are suggested, including a configuration strategy for routers that would allow for the routing of magic packets while still preventing harmful subnet directed broadcasts from being routed. Options that do not require any configuration of the network are also explored. It was also discovered that Apple iMac's network interface cards do not support the ability to wake the machine from a shutdown state. As this is a hardware issue there is little that can be done to circumvent the problem. OS X does allow for an iMac to be woken from a sleeping state by magic packet. Therefore LiteSwitch is able to send iMacs to sleep and still be able to wake them, or it can shut them down remotely but then it will lose control of that machine until it is turned on manually.

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