hpr-knowledge-base/hpr_transcripts/hpr3684.txt

Episode: 3684
Title: HPR3684: Wake on Lan
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3684/hpr3684.mp3
Transcribed: 2025-10-25 03:48:39

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This is Hacker Public Radio Episode 3,684 for Thursday the 15th of September 2022.
Today's show is entitled Wake on Land.
It is hosted by JWP and is about 10 minutes long.
It carries a clean flag.
The summary is Wake on Land Motherboard Feature.
Good day.
I'm JWP and today I want to talk to you about the WOL support.
First off, what does WOL stand for?
WOL stands for Wake on Land.
Your computer on computing, Wake on Land or capital W, little O, big L is a networking protocol
that provides the ability to configure.
It provides to be started from a lower power state using a special signal over the network
also referred to as the magic packet.
You can think of it as a remote power button for your computer.
And if you go to the Wiki, it says it's either an Ethernet or token-ring computer networking
standard that allows the computer to be awakened by network message.
And this message is sent to the target computer by a program executed on a device connected
to the same local area network.
And it's possible to initiate the message from another network by using the subnet
directly broadcast or a WOL gateway service.
Equivalent terms include Wake on Land, which is a remote wake up power on power up by land,
resume by land, resume on land, wake up on land.
And this is all basically the same technology.
If the computer is being awakened communicating via Wi-Fi, a supplementary standard called Wake on wireless land must be employed.
So the WOL and WOL VLAN standards are supplemented by vendors to provide protocol transparent on-demand services.
For example, Apple Bundrore, Wake on demand, Sweet Proxy feature is something that uses.
So it all sort of works on the magic packet symbol.
And so it's gone on for a really long time too.
It started in 96 when Intel and IBM formed the Advanced Manageability Alliance,
or the AMA, and then 97 the Alliance introduced the Wake on Land technology.
So this is a very old technology.
Ethernet connections including home and work, and networks, wireless data networks, and internet itself are based on frames between computers.
WOL is implemented using a specifically designed frame called the Magic Packet,
which is sent to all computers in a network, along with the computer to be awakened.
And the Magic Packet contains a MAC address of the destination computer identifying the number of built into each network interface.
And so, as you know, with the networking, everything has a MAC address.
So it can be specific to there.
And it's unique, because it's unique, the number of that's how it works.
And Power Downer turned off the computers that are capable to Wake on Land will contain certain network devices available to listen to incoming packets in low power mode
while the system is powered down.
If a Magic Packet is received at the direct to device MAC address, then it signals the computer to supply the motherboard and initiate a system wake up.
And in the same way as pressing a power button we do.
The Magic Packet can be sent on a layer, on link layer layer 2 on the OSI mode, and when sent is broadcasted to attach devices on a given network using the network broadcast address.
The IP address in the layer 3 of the OSI model is not used.
The Magic Packet is sent on the data link layer 2 in the OSI mode.
No, that's not it.
Because Wake on Land is built upon a broadcasting technology, it can generally only be used in the current network subset.
There are such and so, and Wake on Land can operate across a network and practice given the appropriate configuration hardware, including remote wake up across the internet.
In order to wake on land to work, parts of the network interface need to stay on, and this consumes a small amount of power, a standby power, much less than normal operating power.
And the link speed is usually reduced to the lowest possible speed as not to waste power.
Gigabit internet, Nick only maintains a 10 NBS link.
Dislaping Wake on land when not needed can slightly reduce power consumption on computers that are switched off but still plug into the power socket.
The power drain comes in consideration when battery powered devices such as laptops can also deplete the battery even when the device is completely shut down.
Okay, so let's talk a little bit more about the Magic Packet.
The Magic Packet is a frame most often sent as a broadcast when it contains somewhere in its payload, six bytes of all, 255 parentheses, FFFF, FFFF, FFFF, FFFF, and the hexademo, followed by 16 repetitions of the target's 48-bit MAC address for a total of 102 bytes.
Since the Magic Packet is only scanned for the string above and not actually passed by the FFFF protocol stack, it can be sent as a payload of any network and transport layer protocol.
Although it's typically sent as a UDP datagram to port zero, which is a reserve port number, echo protocol or discord protocol or directly over the internet as a ether type OXO842.
The connection is orientated in the transport layer like TCP and is less suited for this task as it requires establishing an active connection before sending user data.
The Magic Packet has some limitations and its first limitation is it requires a MAC address and also may require a secure sign-on password.
It does not provide delivery confirmation, so you don't know if it wakes up.
It may not work outside of a local network. It requires hardware support of the wake on LAN on the destination of Peter.
Most of the 802 11 wireless interfaces do not maintain a low power state and cannot receive the Magic Packet.
If you're doing 802 11 on the wireless, it doesn't really happen.
I mean, technically, there's all kinds of things to think about. You got security considerations on authorized access, interactions with networks, but in a home environment or even a small business environment, if they get past your router, you have more trouble.
If he's in there and he can send the wake on LAN to a specific MAC address and you've messed up, he or she is already inside.
What about the hardware? Your power supply has to be an ATX 201 and you have to have a network interface card that does it.
Believe it or not, a lot of motherboards do out of the box. Just check your motherboard paperwork.
Some operating systems control the wake on LAN behavior via NIC drivers.
In other words, they have to have a PCI 22 standard with a compliant 22 network adapter and do not usually require a wake on LAN cable as required standby powers related through the PCI bus.
If you want to support PME power events, you have to go into your BIOS and enable it.
I hope you have a great day. This is JWP. Enjoy the podcast.
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