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.
Okay, so first off, what does WOL stand for?
WOL stands for Wake on Land and the so on your computer, computing Wake on Land, our
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.
If you go to the Wiki, it says it's either an ethernet or token ring computer networking
standard that allows a computer to be awakened by network message and this message is sent
to the target computer by program executed on a device connected to the sample local area
network and it's possible to initiate the message from another network by using the subnet
extracted broadcast or a WOL gateway service equivalent terms include Wake on Land, which
is a remote wake up power on by land, power up by land, resume by land, resume on land, wake
up on land.
This is all basically the same technology.
The computer is being awakened communicating via a supplementary standard called Wake
on Wireless Land must be employed.
The WOL and WOL VLAN standards are supplemented by vendors to provide protocol transparent
on demand services.
For example, Apple Bondor, Wake on Demand, Sweet Proxy Feature is something that uses.
So it also works on the magic packet symbol and it's gone on for a really long time
to start it in 96, when Intel and IBM formed the advanced management build deal lines
or the MAA and in 97 the alliance introduced the Wake on Land technology.
So this is a very old technology.
Even that connections including home and work and networks wireless data networks and Internet
itself are based on frames between computers, WOL, it's implemented using a specifically
designed frame called the Magic Packet which is sent to all computers and a network
a moment computer to be awakened and the Magic Packet contains the MAC address of the
destination computer identifying the number of built into each network interface.
And so as you know with 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
down or turned off the computers 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 directed to device MAC address then they can signal
the computer to supply the motherboard and initiate a system Wake up.
In the same way as pressing a power button we do.
The Magic Packet can be sent on a layer on the link layer layer 2 on the OSI mode and
when sent is broadcasted to attached devices on the 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 now 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 a 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, Nik only maintains a 10 MBS link.
It's late that everyone 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 acceleration when battery power devices such as laptops can also
deplete the battery even when their devices 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 his pay loan 6 bytes of all 2.5 parentheses FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF and the hexedamal
followed by 16 repetitions of the targets 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 full prototype stack, it can be sent as a pay load of any network and transferred
layer protocol. Although it's typically sent as a UDUDP data ground to port 0 which is a
reserve port number, echo protocol or discord protocol or directly over the internet
as a ether type OXOA42.
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 made 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 land on the destination computer.
Most of the 802-11 wireless interfaces do not maintain a low power state and cannot receive
the Magic Packet.
So if you're doing 802-11 on the wireless, it doesn't really happen.
So that's sort of, 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.
So if he's in there and he can send the wake on land and command to a specific MAC address
and you've messed up, he or she is already inside.
So what about the hardware and the, so your power supply has to be an ATX-201 and you have
to have a network interface card that doesn't, and believe it or not, a lot of motherboards
do out of the box, so just check your motherboard paperwork.
Some operating systems control the wake on land behavior via Nick drivers and so the motherboards
they have to have a PCI-2-2 standard with a compliant 2-2 network adapter and do not usually
require a wake on land cable as required standby powers related through the PCI bus.
And so if you're, you want to, 2-2, and it supports PME power events and so you, you
have to go into your bios and able it.
Okay, hey, I hope you have a great day, this is Jeremy Pea, enjoy the podcast.
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