Wake On LAN and the Magic Packet

You hear a lot about Wake On LAN(WOL) in relation to remote Manageability. Let me try to explain what this is really all about.

"Wake on LAN" as the name suggests is a network standard that allows you to remotely (over a network connection) power up your computer when it is completely powered off -- well, assuming your computer is still connected to the power supply :-)

For example: Let us say you at work and want to pick up a file on your home computer and your machine is powered off. You can use the WOL standard to remotely turn-on your machine from a web browser or even your mobile phone, pick up your file and then shut down your home computer. Imagine the alternative where you have to physically power-up the computer at home before you can get any data out of it.

I used this feature a few years ago when I was out of town on an extended business trip. I wanted to intelligently control the lights in my home, just so that it creates an impression that somebody was at home (well, I know I could have purchased the auto day-light sensitive lights... but, I wanted to be a little geeky). I used my computer to control a few lights in my house and then used the WOL features to power-up my computer turn on the lights and then powered down my computer remotely. It all worked great and it was really cool... but I used this feature exactly twice over the two month period I was away from home. Well .. All this gives a lot of fodder for my wife to complain. Another example being .. I spent like 3 whole weekends and close to $150 setting up a vegetable garden for a output of few tomatoes and a few cucumbers.

So, how does this really work? It is really simple... the computer is powered off, but some power is reserved for the network card. The network card listens for a specific data packet (unique identification data for your computer), called as the "MAGIC PACKET". The magic packet is broadcast on the network and the listening computer receives this packet, checks the packet for correct information and then computer is powered up.

Please note that this is not possible if your computer does not support WOL capabilities. The power supply, network card, mother board, etc. all have to support WOL.

With that said the WOL features are really powerful and historically speaking you can say the Wake On LAN gave birth to the remote manageability evolution.
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