Concept
Wake-on-LAN (WoL or WOL) is an Ethernet or Token Ring computer networking standard that allows a computer to be turned on or awakened from sleep mode by a network message. 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 awakened is communicating via Wi-Fi, a supplementary standard called Wake on Wireless LAN (WoWLAN) must be employed. The message is usually sent to the target computer by a program executed on a device connected to the same local area network. It is also possible to initiate the message from another network by using subnet directed broadcasts or a WoL gateway service. 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 (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 frames sent between computers. WoL is implemented using a specially designed frame called a magic packet, which is sent to all computers in a network, among them the computer to be awakened. The magic packet contains the MAC address of the destination computer, an identifying number built into each network interface controller (NIC), that enables it to be uniquely recognized and addressed on a network. Powered-down 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 that is directed to the device's MAC address is received, the NIC signals the computer's power supply or motherboard to initiate system wake-up, in the same way that pressing the power button would do. The magic packet is sent on the data link layer (layer 2 in the OSI model) and when sent, is broadcast to all attached devices on a given network, using the network broadcast address; the IP address (which relates to the internet layer) is not used.
