Embodiments include a main host system of the client computer, and a network event notification system, including a networking subsystem that communicates with a network server to act as a proxy for the client computer when the main host system of the client computer is in a sleep state. The networking subsystem awaits a synchronization packet initiated by the network server, or polls the network server to determine whether data is available. The computing device operates an associated network subsystem while the main host system of the computing device is in a sleep state, and receives data via the network subsystem indicating that content is available to the computing device. Policy is then invoked to determine whether to wake at least part of the main host system to handle the content. A target duty cycle mechanism is also provided to control the average power consumption during wake and sleep cycling.