Bonjour Sleep Proxy


Apple's Bonjour Sleep Proxy service is an open source
component of zero configuration networking, designed to assist in reducing power consumption of networked electronic devices. A device acting as a sleep proxy server will respond to Multicast DNS queries for another, compatible device which has gone into low power mode. The low-power-mode device remains asleep while the sleep proxy server responds to any Multicast DNS queries.
When the sleep proxy server sees a query which requires the low-power-mode device to wake up, the sleep proxy server sends a special wake-up-packet to the low-power-mode device. Finally, communication parameters are updated via Multicast DNS and normal communications proceed.
Apple Inc. describes the service as Bonjour Sleep Proxy in their support documents. The service supports the Wake on Demand feature, first offered in Mac OS X Snow Leopard.

Details

Address resolution protocol

The sleep proxy service responds to address resolution protocol requests on behalf of the low-power-mode device:
When a sleep proxy sees an IPv4 ARP or IPv6 ND Request for one of the sleeping device's addresses, it answers on behalf of the sleeping device, without waking it up, giving its own MAC address as the current owner of that address.

This may appear confusing to network administrators who are not expecting the behaviour of changing MAC addresses.

Wireless magic packet

In case the low-power-mode device is communicating via Wi-Fi, the wake-up-packet is sent via Wireless Multimedia Extensions. This was not possible in previous implementations of Wake on LAN. The wireless hardware must be updated enough to include WMM support. Apple provides instructions for checking compatibility with this feature for Macintosh computers.

Supported services and examples

The sleep proxy service is able to advertise any Bonjour-supported services, while the host computer sleeps. Some examples of supported services are:
has a .

Implementations

Implementations on a local area network can be seen with Bonjour Browser.