Wake on LAN
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Wake on LAN (WoL) refers to the ability to switch on remote computers through special network packets. This feature is very similar to WoM (Zero Voltage Wake on Modem), except it goes through a local area network and requires a specific 'activating' utility to send the signal to the network card to make it work. Both AMD and IBM claim that WoL was their own idea but really, who gives a rat's arse; it's a great piece of technology and it's free! Hee-hee!
Much like a modern television set (don't you love that word 'modern', it's sooo..contemporary), a computer which is Advanced Configuration Power Interface (ACPI) compliant can be turned on remotely. While you can (currently) only turn your telly on from within a certain distance, WoL allows you to remotely start a computer from anywhere in the world, across the wide expanse of the internet!
Hardware requirements
Green PC, motherboard BIOS support, network cards, PCI 2.2, Operating system support (Windows 95+)
Motherboard Most modern ATX motherboards should have a 3-pin Wake-on-LAN connector near the PCI slots and should included BIOS support for Wake-on-LAN power up. If you have an Award BIOS check the Power Management Setup for this option.
Network Card The network card should also include a 3-pin Wake-on-LAN connector. One of the network cards that includes this connector is the Intel Pro/100+ (chipset 82559)
Plugging it in
To use the Wake On LAN function, you must have a network card with a chipset that supports this feature and a connecting cable from the NIC card to the supporting motherboard's 3-pin WoL connector. On-board NICs usually have the WoL connectivity built-in.
  
Geek's Only: The 'Magic' Sequence
OK if you really want to know how this stuff works, here's it is. Better make sure you get a bit more of a life though..
If the MAC Address of a target computer is 01:02:03:04:05:06 (6 bytes), then the LAN controller of that machine should be looking for the following sequence inside the frame:
FFFFFFFFFFFF010203040506010203040506010203040506010203040506
010203040506010203040506010203040506010203040506010203040506
010203040506010203040506010203040506010203040506010203040506
010203040506010203040506
Wake-up frame A Wake-up frame is a special data packet containing the MAC Address of the remote network card. Somewhere in this frame should exist a byte stream (magic sequence) composed by, at the least, 16 times the repetition of the MAC Address and preceded by a synchronization stream of 6 bytes of FFh.
Getting the MAC Address
A MAC Address is a six octet (48 bits) number that uniquelly identifies every network interface card (NIC). The first three octets (24 bits) are known as the Organizationally Unique Identifier (OUI) and identifies its manufacturer.
Under Windows, type go to START | Run and type COMMAND. In the ensuing command prompt window, type IPCONFIG • /ALL. Microsoft calls it the 'Physical Address' here, just to confuse you. Also try out ARP Viewer on Goth.
Under Unix/Linux, type IFCONFIG
Sending the signal
Depicus supplies two freeware versions of their own startup app; a GUI (WoLgui.exe, below) and a command line version (WoLcmd.exe). The startup signal can be run straight from either of these executables, without the need for prior installation.
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Ok so you've got compliant hardware, the little WoL lead is nestling comfortably betwixt NIC and motherboard and the BIOS has its WoL setting enabled. The target computer is shut down, but power still lurks within the NIC card and it waits for that special signal on port number 7 (default).
Meanwhile at the other end you fire up your WoL Activation Utility (I'm really not comfortable with 'magic packet' - what is this, Playschool!?), point it to the sleeper's IP/MAC Address and voila! Instant boot up. Isn't technology wonderful..
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![Remote [and local] shutdown](images/wake_on_lan_shutdown.gif)
