Bonjour Sleep Proxy

Bonjour Sleep Proxy is a feature of Apple's Bonjour networking technology that enables devices to remain accessible on a network even when they are in a low-power sleep mode. This is especially useful for devices that would typically not be reachable by other devices when they enter sleep to conserve energy. When a device with Bonjour Sleep Proxy is in sleep mode, a proxy service on your network (often running on a router or another always-on device) can respond to requests on behalf of the sleeping device.