Wake-on-LAN

Wake-on-LAN (WoL) is an Ethernet or token ring computer networking standard that allows a computer to be turned on or woken up by a network message.

The message is usually sent to the target computer by a program executed on a device connected to the same local area network, such as a smartphone. It is also possible to initiate the message from another network by using subnet directed broadcasts or a WOL gateway service. Equivalent terms include wake on WAN, remote wake-up, power on by LAN, power up by LAN, resume by LAN, resume on LAN and wake up on LAN. If the computer being woken up is communicating via Wi-Fi, a supplementary standard called Wake on Wireless LAN (WoWLAN) must be employed.

The WOL and WoWLAN standards are often supplemented by vendors to provide protocol-transparent on-demand services, for example in the Apple Bonjour wake-on-demand (Sleep Proxy) feature.

In October 1996, Intel and IBM formed the Advanced Manageability Alliance (AMA). In April 1997, this alliance introduced the Wake-on-LAN technology.

Ethernet connections, including home and work networks, wireless data networks and the Internet itself, are based on packets of data sent between computers. Wake-on-LAN ("WOL") is implemented using a specially designed packet called a magic packet, which is sent to all computers in a network, among them the computer to be woken up. The magic packet contains the MAC address of the destination computer, an identifying number built into each network interface card ("NIC") or other ethernet device in a computer, that enables it to be uniquely recognized and addressed on a network. Powered-down or turned off computers capable of Wake-on-LAN will contain network devices able to "listen" to incoming packets in low-power mode while the system is powered down. If a magic packet is received that is directed to the device's MAC address, the NIC signals the computer's power supply or motherboard to initiate system wake-up, much in the same way as pressing the power button would do.

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