<s>
Wake-on-LAN	B-Protocol
(	O
WoL	O
or	O
WOL	O
)	O
is	O
an	O
Ethernet	O
or	O
Token	B-Device
Ring	I-Device
computer	B-Architecture
networking	I-Architecture
standard	O
that	O
allows	O
a	O
computer	O
to	O
be	O
turned	O
on	O
or	O
awakened	O
from	O
sleep	O
mode	O
by	O
a	O
network	O
message	O
.	O
</s>
<s>
Equivalent	O
terms	O
include	O
wake	O
on	O
WAN	O
,	O
remote	B-Protocol
wake-up	I-Protocol
,	O
power	O
on	O
by	O
LAN	B-General_Concept
,	O
power	O
up	O
by	O
LAN	B-General_Concept
,	O
resume	O
by	O
LAN	B-General_Concept
,	O
resume	O
on	O
LAN	B-General_Concept
and	O
wake	O
up	O
on	O
LAN	B-General_Concept
.	O
</s>
<s>
If	O
the	O
computer	O
being	O
awakened	O
is	O
communicating	O
via	O
Wi-Fi	O
,	O
a	O
supplementary	O
standard	O
called	O
Wake	O
on	O
Wireless	O
LAN	B-General_Concept
(	O
WoWLAN	B-Protocol
)	O
must	O
be	O
employed	O
.	O
</s>
<s>
The	O
message	O
is	O
usually	O
sent	O
to	O
the	O
target	O
computer	O
by	O
a	O
program	O
executed	O
on	O
a	O
device	O
connected	O
to	O
the	O
same	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
initiate	O
the	O
message	O
from	O
another	O
network	O
by	O
using	O
subnet	O
directed	O
broadcasts	B-Operating_System
or	O
a	O
WoL	O
gateway	O
service	O
.	O
</s>
<s>
The	O
WoL	O
and	O
WoWLAN	B-Protocol
standards	O
are	O
often	O
supplemented	O
by	O
vendors	O
to	O
provide	O
protocol-transparent	O
on-demand	O
services	O
,	O
for	O
example	O
in	O
the	O
Apple	B-Application
Bonjour	I-Application
wake-on-demand	O
(	O
Sleep	B-Protocol
Proxy	I-Protocol
)	O
feature	O
.	O
</s>
<s>
In	O
October	O
1996	O
,	O
Intel	O
and	O
IBM	O
formed	O
the	O
Advanced	B-Protocol
Manageability	I-Protocol
Alliance	I-Protocol
(	O
AMA	O
)	O
.	O
</s>
<s>
In	O
April	O
1997	O
,	O
this	O
alliance	O
introduced	O
the	O
Wake-on-LAN	B-Protocol
technology	O
.	O
</s>
<s>
Ethernet	O
connections	O
,	O
including	O
home	O
and	O
work	O
networks	O
,	O
wireless	O
data	B-Architecture
networks	I-Architecture
,	O
and	O
the	O
Internet	O
itself	O
,	O
are	O
based	O
on	O
frames	O
sent	O
between	O
computers	O
.	O
</s>
<s>
WoL	O
is	O
implemented	O
using	O
a	O
specially	O
designed	O
frame	B-Protocol
called	O
a	O
magic	O
packet	O
,	O
which	O
is	O
sent	O
to	O
all	O
computers	O
in	O
a	O
network	O
,	O
among	O
them	O
the	O
computer	O
to	O
be	O
awakened	O
.	O
</s>
<s>
The	O
magic	O
packet	O
contains	O
the	O
MAC	O
address	O
of	O
the	O
destination	O
computer	O
,	O
an	O
identifying	O
number	O
built	O
into	O
each	O
network	B-Protocol
interface	I-Protocol
card	I-Protocol
(	O
"	O
NIC	O
"	O
)	O
or	O
other	O
Ethernet	O
device	O
in	O
a	O
computer	O
,	O
that	O
enables	O
it	O
to	O
be	O
uniquely	O
recognized	O
and	O
addressed	O
on	O
a	O
network	O
.	O
</s>
<s>
Powered	O
down	O
or	O
turned	O
off	O
computers	O
capable	O
of	O
Wake-on-LAN	B-Protocol
will	O
contain	O
network	O
devices	O
able	O
to	O
"	O
listen	O
"	O
to	O
incoming	O
packets	O
in	O
low-power	O
mode	O
while	O
the	O
system	O
is	O
powered	O
down	O
.	O
</s>
<s>
If	O
a	O
magic	O
packet	O
is	O
received	O
that	O
is	O
directed	O
to	O
the	O
device	O
's	O
MAC	O
address	O
,	O
the	O
NIC	O
signals	O
the	O
computer	O
's	O
power	O
supply	O
or	O
motherboard	B-Device
to	O
initiate	O
system	O
wake-up	O
,	O
in	O
the	O
same	O
way	O
that	O
pressing	O
the	O
power	O
button	O
would	O
do	O
.	O
</s>
<s>
The	O
magic	O
packet	O
is	O
sent	O
on	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
layer	B-Protocol
2	I-Protocol
in	O
the	O
OSI	O
model	O
)	O
and	O
when	O
sent	O
,	O
is	O
broadcast	B-Operating_System
to	O
all	O
attached	O
devices	O
on	O
a	O
given	O
network	O
,	O
using	O
the	O
network	O
broadcast	B-Protocol
address	I-Protocol
;	O
the	O
IP	O
address	O
(	O
layer	O
3	O
in	O
the	O
OSI	O
model	O
)	O
is	O
not	O
used	O
.	O
</s>
<s>
Because	O
Wake-on-LAN	B-Protocol
is	O
built	O
upon	O
broadcast	B-Operating_System
technology	O
,	O
it	O
can	O
generally	O
only	O
be	O
used	O
within	O
the	O
current	O
network	O
subnet	O
.	O
</s>
<s>
There	O
are	O
some	O
exceptions	O
,	O
though	O
,	O
and	O
Wake-on-LAN	B-Protocol
can	O
operate	O
across	O
any	O
network	O
in	O
practice	O
,	O
given	O
appropriate	O
configuration	O
and	O
hardware	O
,	O
including	O
remote	B-Protocol
wake-up	I-Protocol
across	O
the	O
Internet	O
.	O
</s>
<s>
In	O
order	O
for	O
Wake-on-LAN	B-Protocol
to	O
work	O
,	O
parts	O
of	O
the	O
network	O
interface	O
need	O
to	O
stay	O
on	O
.	O
</s>
<s>
a	O
Gigabit	O
Ethernet	B-Protocol
NIC	I-Protocol
maintains	O
only	O
a	O
10Mbit/s	O
link	O
)	O
.	O
</s>
<s>
Disabling	O
Wake-on-LAN	B-Protocol
when	O
not	O
needed	O
can	O
very	O
slightly	O
reduce	O
power	O
consumption	O
on	O
computers	O
that	O
are	O
switched	O
off	O
but	O
still	O
plugged	O
into	O
a	O
power	O
socket	O
.	O
</s>
<s>
The	O
magic	O
packet	O
is	O
a	O
frame	B-Protocol
that	O
is	O
most	O
often	O
sent	O
as	O
a	O
broadcast	B-Operating_System
and	O
that	O
contains	O
anywhere	O
within	O
its	O
payload	O
6	O
bytes	B-Application
of	O
all	O
255	O
(	O
FF	O
FF	O
FF	O
FF	O
FF	O
FF	O
in	O
hexadecimal	O
)	O
,	O
followed	O
by	O
sixteen	O
repetitions	O
of	O
the	O
target	O
computer	O
's	O
48-bit	O
MAC	O
address	O
,	O
for	O
a	O
total	O
of	O
102	O
bytes	B-Application
.	O
</s>
<s>
Since	O
the	O
magic	O
packet	O
is	O
only	O
scanned	O
for	O
the	O
string	O
above	O
,	O
and	O
not	O
actually	O
parsed	O
by	O
a	O
full	O
protocol	O
stack	O
,	O
it	O
could	O
be	O
sent	O
as	O
payload	O
of	O
any	O
network	O
-	O
and	O
transport-layer	O
protocol	O
,	O
although	O
it	O
is	O
typically	O
sent	O
as	O
a	O
UDP	B-Protocol
datagram	B-Protocol
to	O
port	B-Protocol
0	O
(	O
reserved	O
port	B-Protocol
number	I-Protocol
)	O
,	O
7	O
(	O
Echo	B-Protocol
Protocol	I-Protocol
)	O
or	O
9	O
(	O
Discard	B-Protocol
Protocol	I-Protocol
)	O
,	O
or	O
directly	O
over	O
Ethernet	O
as	O
EtherType	B-Protocol
0x0842	O
.	O
</s>
<s>
A	O
connection-oriented	B-Protocol
transport-layer	O
protocol	O
like	O
TCP	B-Protocol
is	O
less	O
suited	O
for	O
this	O
task	O
as	O
it	O
requires	O
establishing	O
an	O
active	O
connection	O
before	O
sending	O
user	O
data	O
.	O
</s>
<s>
The	O
Wake-on-LAN	B-Protocol
implementation	O
is	O
designed	O
to	O
be	O
very	O
simple	O
and	O
to	O
be	O
quickly	O
processed	O
by	O
the	O
circuitry	O
present	O
on	O
the	O
network	B-Protocol
interface	I-Protocol
card	I-Protocol
with	O
minimal	O
power	O
requirement	O
.	O
</s>
<s>
Because	O
Wake-on-LAN	B-Protocol
operates	O
below	O
the	O
IP	O
protocol	O
layer	O
,	O
IP	O
addresses	O
and	O
DNS	O
names	O
are	O
meaningless	O
and	O
so	O
the	O
MAC	O
address	O
is	O
required	O
.	O
</s>
<s>
A	O
principal	O
limitation	O
of	O
standard	O
broadcast	B-Operating_System
Wake-on-LAN	B-Protocol
is	O
that	O
broadcast	B-Operating_System
packets	I-Operating_System
are	O
generally	O
not	O
routed	O
.	O
</s>
<s>
Subnet	O
directed	O
broadcasts	B-Operating_System
(	O
SDB	O
)	O
may	O
be	O
used	O
to	O
overcome	O
this	O
limitation	O
.	O
</s>
<s>
SDB	O
may	O
require	O
changes	O
to	O
intermediate	O
router	B-Protocol
configuration	O
.	O
</s>
<s>
Subnet	O
directed	O
broadcasts	B-Operating_System
are	O
treated	O
like	O
unicast	O
network	O
packets	O
until	O
processed	O
by	O
the	O
final	O
(	O
local	O
)	O
router	B-Protocol
.	O
</s>
<s>
This	O
router	B-Protocol
then	O
broadcasts	B-Operating_System
the	O
packet	O
using	O
layer	B-Protocol
2	I-Protocol
broadcast	B-Operating_System
.	O
</s>
<s>
This	O
technique	O
allows	O
a	O
broadcast	B-Operating_System
to	O
be	O
initiated	O
on	O
a	O
remote	O
network	O
but	O
requires	O
all	O
intervening	O
routers	B-Protocol
to	O
forward	O
the	O
SDB	O
.	O
</s>
<s>
Wake-on-LAN	B-Protocol
can	O
be	O
a	O
difficult	O
technology	O
to	O
implement	O
,	O
because	O
it	O
requires	O
appropriate	O
BIOS/UEFI	O
,	O
network	B-Protocol
card	I-Protocol
and	O
,	O
sometimes	O
,	O
operating	B-General_Concept
system	I-General_Concept
and	O
router	B-Protocol
support	O
to	O
function	O
reliably	O
.	O
</s>
<s>
In	O
that	O
case	O
,	O
software	O
tools	O
like	O
a	O
packet	B-Protocol
analyzer	I-Protocol
can	O
help	O
with	O
Wake-on-LAN	B-Protocol
troubleshooting	O
as	O
they	O
allow	O
confirming	O
(	O
while	O
the	O
PC	O
is	O
still	O
on	O
)	O
that	O
the	O
magic	O
packet	O
is	O
indeed	O
visible	O
to	O
a	O
particular	O
computer	O
's	O
NIC	O
.	O
</s>
<s>
In	O
some	O
cases	O
they	O
also	O
confirm	O
that	O
the	O
packet	O
was	O
destined	O
for	O
a	O
specific	O
PC	O
or	O
sent	O
to	O
a	O
broadcast	B-Protocol
address	I-Protocol
and	O
they	O
can	O
additionally	O
show	O
the	O
packet	O
's	O
internals	O
.	O
</s>
<s>
Starting	O
with	O
Windows	O
Vista	O
,	O
the	O
operating	B-General_Concept
system	I-General_Concept
logs	O
all	O
wake	O
sources	O
in	O
the	O
"	O
System	O
"	O
event	O
log	O
.	O
</s>
<s>
Magic	O
packets	O
are	O
sent	O
via	O
the	O
data	B-Protocol
link	I-Protocol
or	I-Protocol
OSI-2	I-Protocol
layer	I-Protocol
,	O
which	O
can	O
be	O
used	O
or	O
abused	O
by	O
anyone	O
on	O
the	O
same	O
LAN	B-General_Concept
,	O
unless	O
the	O
L2	O
LAN	B-General_Concept
equipment	O
is	O
capable	O
of	O
(	O
and	O
configured	O
for	O
)	O
filtering	O
such	O
traffic	O
to	O
match	O
site-wide	O
security	O
requirements	O
.	O
</s>
<s>
Firewalls	B-Application
may	O
be	O
used	O
to	O
prevent	O
clients	O
among	O
the	O
public	O
WAN	O
from	O
accessing	O
the	O
broadcast	B-Operating_System
addresses	O
of	O
inside	O
LAN	B-General_Concept
segments	O
,	O
or	O
routers	B-Protocol
may	O
be	O
configured	O
to	O
ignore	O
subnet-directed	O
broadcasts	B-Operating_System
(	O
see	O
above	O
)	O
.	O
</s>
<s>
It	O
allows	O
users	O
to	O
store	O
within	O
the	O
NIC	O
a	O
hexadecimal	O
password	O
of	O
6	O
bytes	B-Application
.	O
</s>
<s>
This	O
security	O
measure	O
significantly	O
decreases	O
the	O
risk	O
of	O
successful	O
brute	O
force	O
attacks	O
,	O
by	O
increasing	O
the	O
search	O
space	O
by	O
48	O
bits	O
(	O
6	O
bytes	B-Application
)	O
,	O
up	O
to	O
296	O
combinations	O
if	O
the	O
MAC	O
address	O
is	O
entirely	O
unknown	O
.	O
</s>
<s>
Still	O
,	O
only	O
a	O
few	O
NIC	O
and	O
router	B-Protocol
manufacturers	O
support	O
such	O
security	O
features	O
.	O
</s>
<s>
Abuse	O
of	O
the	O
Wake-on-LAN	B-Protocol
feature	O
only	O
allows	O
computers	O
to	O
be	O
switched	O
on	O
;	O
it	O
does	O
not	O
in	O
itself	O
bypass	O
password	O
and	O
other	O
forms	O
of	O
security	O
,	O
and	O
is	O
unable	O
to	O
power	O
off	O
the	O
machine	O
once	O
on	O
.	O
</s>
<s>
However	O
,	O
many	O
client	O
computers	O
attempt	O
booting	O
from	O
a	O
PXE	B-Device
server	O
when	O
powered	O
up	O
by	O
WoL	O
.	O
</s>
<s>
Therefore	O
,	O
a	O
combination	O
of	O
DHCP	B-Protocol
and	O
PXE	B-Device
servers	O
on	O
the	O
network	O
can	O
sometimes	O
be	O
used	O
to	O
start	O
a	O
computer	O
with	O
an	O
attacker	O
's	O
boot	O
image	O
,	O
bypassing	O
any	O
security	O
of	O
the	O
installed	O
operating	B-General_Concept
system	I-General_Concept
and	O
granting	O
access	O
to	O
unprotected	O
,	O
local	O
disks	O
over	O
the	O
network	O
.	O
</s>
<s>
The	O
use	O
of	O
Wake-on-LAN	B-Protocol
technology	O
on	O
enterprise	O
networks	O
can	O
sometimes	O
conflict	O
with	O
network	O
access	O
control	O
solutions	O
such	O
as	O
802.1X	O
or	O
MAC-based	O
authentication	O
,	O
which	O
may	O
prevent	O
magic	O
packet	O
delivery	O
if	O
a	O
machine	O
's	O
WoL	O
hardware	O
has	O
not	O
been	O
designed	O
to	O
maintain	O
a	O
live	O
authentication	O
session	O
while	O
in	O
a	O
sleep	O
state	O
.	O
</s>
<s>
Some	O
PCs	O
include	O
technology	O
built	O
into	O
the	O
chipset	B-Device
to	O
improve	O
security	O
for	O
Wake-on-LAN	B-Protocol
.	O
</s>
<s>
For	O
example	O
,	O
Intel	B-Application
AMT	I-Application
(	O
a	O
component	O
of	O
Intel	B-Architecture
vPro	I-Architecture
technology	O
)	O
,	O
includes	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
,	O
an	O
industry-standard	O
protocol	O
that	O
strengthens	O
encryption	O
.	O
</s>
<s>
AMT	O
uses	O
TLS	B-Protocol
encryption	I-Protocol
to	O
secure	O
an	O
out-of-band	B-Application
communication	O
tunnel	O
to	O
an	O
AMT-based	O
PC	O
for	O
remote	O
management	O
commands	O
such	O
as	O
Wake-on-LAN	B-Protocol
.	O
</s>
<s>
AMT	O
secures	O
the	O
communication	O
tunnel	O
with	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
AES	B-Algorithm
)	O
128-bit	O
encryption	O
and	O
RSA	B-Architecture
keys	O
with	O
modulus	O
lengths	O
of	O
2,048	O
bits	O
.	O
</s>
<s>
Because	O
the	O
encrypted	O
communication	O
is	O
out-of-band	B-Application
,	O
the	O
PC	O
's	O
hardware	O
and	O
firmware	O
receive	O
the	O
magic	O
packet	O
before	O
network	O
traffic	O
reaches	O
the	O
software	O
stack	O
for	O
the	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
.	O
</s>
<s>
IT	O
shops	O
using	O
Wake-on-LAN	B-Protocol
through	O
the	O
Intel	B-Application
AMT	I-Application
implementation	O
can	O
wake	O
an	O
AMT	O
PC	O
over	O
network	O
environments	O
that	O
require	O
TLS-based	O
security	O
,	O
such	O
as	O
IEEE	O
802.1X	O
,	O
Cisco	O
Self	O
Defending	O
Network	O
(	O
SDN	O
)	O
,	O
and	O
Microsoft	O
Network	O
Access	O
Protection	O
(	O
NAP	O
)	O
environments	O
.	O
</s>
<s>
Wake-on-LAN	B-Protocol
support	O
is	O
implemented	O
on	O
the	O
motherboard	B-Device
of	O
a	O
computer	O
and	O
the	O
network	B-Protocol
interface	I-Protocol
card	I-Protocol
,	O
and	O
is	O
consequently	O
not	O
dependent	O
on	O
the	O
operating	B-General_Concept
system	I-General_Concept
running	O
on	O
the	O
hardware	O
.	O
</s>
<s>
Some	O
operating	B-General_Concept
systems	I-General_Concept
can	O
control	O
Wake-on-LAN	B-Protocol
behaviour	O
via	O
NIC	O
drivers	O
.	O
</s>
<s>
With	O
older	O
motherboards	B-Device
,	O
if	O
the	O
network	O
interface	O
is	O
a	O
plug-in	O
card	O
rather	O
than	O
being	O
integrated	O
into	O
the	O
motherboard	B-Device
,	O
the	O
card	O
may	O
need	O
to	O
be	O
connected	O
to	O
the	O
motherboard	B-Device
by	O
an	O
additional	O
cable	O
.	O
</s>
<s>
Motherboards	B-Device
with	O
an	O
embedded	O
Ethernet	O
controller	O
which	O
supports	O
Wake-on-LAN	B-Protocol
do	O
not	O
need	O
a	O
cable	O
.	O
</s>
<s>
The	O
power	O
supply	O
must	O
meet	O
ATX	B-Language
2.01	O
specifications	O
.	O
</s>
<s>
Older	O
motherboards	B-Device
must	O
have	O
a	O
WAKEUP-LINK	O
header	O
onboard	O
connected	O
to	O
the	O
network	B-Protocol
card	I-Protocol
via	O
a	O
special	O
3-pin	O
cable	O
;	O
however	O
,	O
systems	O
supporting	O
the	O
PCI	B-Protocol
2.2	I-Protocol
standard	O
and	O
with	O
a	O
PCI	B-Protocol
2.2	I-Protocol
compliant	O
network	B-Protocol
adapter	I-Protocol
card	O
do	O
not	O
usually	O
require	O
a	O
Wake-on-LAN	B-Protocol
cable	O
as	O
the	O
required	O
standby	O
power	O
is	O
relayed	O
through	O
the	O
PCI	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
PCI	B-Protocol
version	O
2.2	O
supports	O
PME	O
(	O
Power	O
Management	O
Events	O
)	O
.	O
</s>
<s>
PCI	B-Protocol
cards	I-Protocol
send	O
and	O
receive	O
PME	O
signals	O
via	O
the	O
PCI	B-Protocol
socket	O
directly	O
,	O
without	O
the	O
need	O
for	O
a	O
Wake-on-LAN	B-Protocol
cable	O
.	O
</s>
<s>
Wake-on-LAN	B-Protocol
usually	O
needs	O
to	O
be	O
enabled	O
in	O
the	O
Power	O
Management	O
section	O
of	O
a	O
PC	B-Device
motherboard	I-Device
's	O
BIOS/UEFI	O
setup	O
utility	O
,	O
although	O
on	O
some	O
systems	O
,	O
such	O
as	O
Apple	O
computers	O
,	O
it	O
is	O
enabled	O
by	O
default	O
.	O
</s>
<s>
On	O
older	O
systems	O
the	O
BIOS/UEFI	O
setting	O
may	O
be	O
referred	O
to	O
as	O
WoL	O
;	O
on	O
newer	O
systems	O
supporting	O
PCI	B-Protocol
version	O
2.2	O
,	O
it	O
may	O
be	O
referred	O
to	O
as	O
PME	O
(	O
Power	O
Management	O
Events	O
,	O
which	O
include	O
WoL	O
)	O
.	O
</s>
<s>
It	O
may	O
also	O
be	O
necessary	O
to	O
configure	O
the	O
computer	O
to	O
reserve	O
standby	O
power	O
for	O
the	O
network	B-Protocol
card	I-Protocol
when	O
the	O
system	O
is	O
shut	O
down	O
.	O
</s>
<s>
In	O
addition	O
,	O
in	O
order	O
to	O
get	O
Wake-on-LAN	B-Protocol
to	O
work	O
,	O
enabling	O
this	O
feature	O
on	O
the	O
network	B-Protocol
interface	I-Protocol
card	I-Protocol
or	O
on-board	O
silicon	O
is	O
sometimes	O
required	O
.	O
</s>
<s>
Details	O
of	O
how	O
to	O
do	O
this	O
depend	O
upon	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
the	O
device	O
driver	O
.	O
</s>
<s>
Laptops	O
powered	O
by	O
the	O
Intel	O
Centrino	O
Processor	O
Technology	O
or	O
newer	O
(	O
with	O
explicit	O
BIOS/UEFI	O
support	O
)	O
allow	O
waking	O
up	O
the	O
machine	O
using	O
wireless	O
Wake	O
on	O
Wireless	O
LAN	B-General_Concept
(	O
WoWLAN	B-Protocol
)	O
.	O
</s>
<s>
In	O
most	O
modern	O
PCs	O
,	O
ACPI	B-Device
is	O
notified	O
of	O
the	O
"	O
waking	O
up	O
"	O
and	O
takes	O
control	O
of	O
the	O
power-up	O
.	O
</s>
<s>
In	O
ACPI	B-Device
,	O
OSPM	O
must	O
record	O
the	O
"	O
wake	O
source	O
"	O
or	O
the	O
device	O
that	O
is	O
causing	O
the	O
power-upthe	O
device	O
being	O
the	O
"	O
Soft	O
"	O
power	O
switch	O
,	O
the	O
NIC	O
(	O
via	O
Wake-on-LAN	B-Protocol
)	O
,	O
the	O
cover	O
being	O
opened	O
,	O
a	O
temperature	O
change	O
,	O
etc	O
.	O
</s>
<s>
The	O
3-pin	O
WoL	O
interface	O
on	O
the	O
motherboard	B-Device
consist	O
of	O
pin-1	O
+5V	O
DC	O
(	O
red	O
)	O
,	O
pin-2	O
Ground	O
(	O
black	O
)	O
,	O
pin-3	O
(	O
green	O
or	O
yellow	O
)	O
.	O
</s>
<s>
By	O
supplying	O
the	O
pin-3	O
wake	O
signal	O
with	O
+5V	O
DC	O
the	O
computer	O
will	O
be	O
triggered	O
to	O
power	O
up	O
provided	O
WoL	O
is	O
enabled	O
in	O
the	O
BIOS/UEFI	O
configuration	O
.	O
</s>
<s>
While	O
WoL	O
hardware	O
or	O
firmware	O
is	O
arguably	O
performing	O
the	O
role	O
of	O
a	O
"	O
server	O
"	O
,	O
Web-based	O
interfaces	O
which	O
act	O
as	O
a	O
gateway	O
through	O
which	O
users	O
can	O
issue	O
WoL	O
packets	O
without	O
downloading	O
a	O
local	O
client	O
often	O
become	O
known	O
as	O
"	O
The	O
Wake	B-Protocol
On	I-Protocol
LAN	I-Protocol
Server	O
"	O
to	O
users	O
.	O
</s>
<s>
Software	O
to	O
send	O
WoL	O
magic	O
packets	O
is	O
available	O
for	O
all	O
modern	O
platforms	O
,	O
including	O
Windows	O
,	O
Macintosh	O
and	O
Linux	O
,	O
plus	O
many	O
smartphones	B-Application
.	O
</s>
<s>
Examples	O
include	O
:	O
Wake	B-Protocol
On	I-Protocol
LAN	I-Protocol
GUI	O
,	O
LAN	B-General_Concept
Helper	O
,	O
Magic	O
Packet	O
Utility	O
,	O
NetWaker	O
for	O
Windows	O
,	O
Nirsoft	O
WakeMeOnLAN	O
,	O
WakeOnLANx	O
,	O
EMCO	O
WOL	O
,	O
Aquila	O
Tech	O
Wake	B-Protocol
on	I-Protocol
LAN	I-Protocol
,	O
ManageEngine	O
WOL	O
utility	O
,	O
FusionFenix	O
and	O
SolarWinds	O
WOL	O
Tool	O
.	O
</s>
<s>
Example	O
source	O
code	O
for	O
a	O
developer	O
to	O
add	O
Wake-on-LAN	B-Protocol
to	O
a	O
program	O
is	O
readily	O
available	O
in	O
many	O
computer	B-Language
languages	I-Language
.	O
</s>
<s>
The	O
following	O
example	O
is	O
in	O
Python	B-Language
3	O
:	O
</s>
<s>
If	O
the	O
sender	O
is	O
on	O
the	O
same	O
subnet	O
(	O
local	B-General_Concept
network	I-General_Concept
,	I-General_Concept
aka	I-General_Concept
LAN	I-General_Concept
)	O
as	O
the	O
computer	O
to	O
be	O
awakened	O
there	O
are	O
generally	O
no	O
issues	O
.	O
</s>
<s>
When	O
sending	O
over	O
the	O
Internet	O
,	O
and	O
in	O
particular	O
where	O
a	O
NAT	B-Protocol
(	O
Network	B-Protocol
Address	I-Protocol
Translator	I-Protocol
)	O
router	B-Protocol
,	O
as	O
typically	O
deployed	O
in	O
most	O
homes	O
,	O
is	O
involved	O
,	O
special	O
settings	O
often	O
need	O
to	O
be	O
set	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
router	B-Protocol
,	O
the	O
computer	O
to	O
be	O
controlled	O
needs	O
to	O
have	O
a	O
dedicated	O
IP	O
address	O
assigned	O
(	O
aka	O
a	O
DHCP	B-Protocol
reservation	O
)	O
.	O
</s>
<s>
Also	O
,	O
since	O
the	O
controlled	O
computer	O
will	O
be	O
"	O
sleeping	O
"	O
except	O
for	O
some	O
electricity	O
on	O
to	O
part	O
of	O
its	O
LAN	B-Protocol
card	I-Protocol
,	O
typically	O
it	O
will	O
not	O
be	O
registered	O
at	O
the	O
router	B-Protocol
as	O
having	O
an	O
active	O
IP	O
lease	O
.	O
</s>
<s>
To	O
ensure	O
the	O
magic	O
packet	O
gets	O
from	O
source	O
to	O
destination	O
while	O
the	O
destination	O
is	O
sleeping	O
,	O
the	O
ARP	O
Binding	O
(	O
also	O
known	O
as	O
IP	O
&	O
MAC	O
binding	O
)	O
must	O
typically	O
be	O
set	O
in	O
a	O
NAT	B-Protocol
router	B-Protocol
.	O
</s>
<s>
This	O
allows	O
the	O
router	B-Protocol
to	O
forward	O
the	O
magic	O
packet	O
to	O
the	O
sleeping	O
computer	O
's	O
MAC	O
adapter	O
at	O
a	O
networking	O
layer	O
below	O
typical	O
IP	O
usage	O
.	O
</s>
<s>
In	O
the	O
NAT	B-Protocol
router	B-Protocol
,	O
ARP	O
binding	O
requires	O
just	O
a	O
dedicated	O
IP	O
number	O
and	O
the	O
MAC	O
address	O
of	O
the	O
destination	O
computer	O
.	O
</s>
<s>
There	O
are	O
some	O
security	O
implications	O
associated	O
with	O
ARP	O
binding	O
(	O
see	O
ARP	O
spoofing	O
)	O
;	O
however	O
,	O
as	O
long	O
as	O
none	O
of	O
the	O
computers	O
connected	O
to	O
the	O
LAN	B-General_Concept
are	O
compromised	O
,	O
an	O
attacker	O
must	O
use	O
a	O
computer	O
that	O
is	O
connected	O
directly	O
to	O
the	O
target	O
LAN	B-General_Concept
(	O
plugged	O
into	O
the	O
LAN	B-General_Concept
via	O
cable	O
,	O
or	O
by	O
breaking	O
through	O
the	O
Wi‑Fi	O
connection	O
security	O
to	O
gain	O
access	O
to	O
the	O
LAN	B-General_Concept
)	O
.	O
</s>
<s>
Most	O
home	O
routers	B-Protocol
are	O
able	O
to	O
send	O
magic	O
packets	O
to	O
LAN	B-General_Concept
;	O
for	O
example	O
,	O
routers	B-Protocol
with	O
the	O
DD-WRT	B-Protocol
,	O
Tomato	B-Protocol
or	O
PfSense	B-Protocol
firmware	O
have	O
a	O
built-in	O
Wake-on-LAN	B-Protocol
client	O
.	O
</s>
<s>
OpenWrt	B-Application
supports	O
both	O
Linux	O
implementations	O
for	O
WoL	O
etherwake	O
and	O
WoLs	O
.	O
</s>
<s>
Most	O
WoL	O
hardware	O
functionally	O
is	O
typically	O
blocked	O
by	O
default	O
and	O
needs	O
to	O
be	O
enabled	O
in	O
using	O
the	O
system	O
BIOS/UEFI	O
.	O
</s>
<s>
Further	O
configuration	O
from	O
the	O
OS	O
is	O
required	O
in	O
some	O
cases	O
,	O
for	O
example	O
via	O
the	O
Device	O
Manager	O
network	B-Protocol
card	I-Protocol
properties	O
on	O
Windows	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
For	O
full	O
support	O
of	O
a	O
device	O
's	O
WoL	O
capabilities	O
(	O
such	O
as	O
the	O
ability	O
to	O
wake	O
from	O
an	O
ACPI	B-Device
S5	O
power	O
off	O
state	O
)	O
,	O
installation	O
of	O
the	O
full	O
driver	O
suite	O
from	O
the	O
network	O
device	O
manufacturer	O
may	O
be	O
necessary	O
,	O
rather	O
than	O
the	O
bare	O
driver	O
provided	O
by	O
Microsoft	O
or	O
the	O
computer	O
manufacturer	O
.	O
</s>
<s>
In	O
most	O
cases	O
correct	O
BIOS/UEFI	O
configuration	O
is	O
also	O
required	O
for	O
WoL	O
to	O
function	O
.	O
</s>
<s>
This	O
is	O
because	O
of	O
a	O
change	O
in	O
the	O
OS	O
behavior	O
which	O
causes	O
network	B-Protocol
adapters	I-Protocol
to	O
be	O
explicitly	O
not	O
armed	O
for	O
WoL	O
when	O
shutdown	O
to	O
these	O
states	O
occurs	O
.	O
</s>
<s>
The	O
feature	O
is	O
controlled	O
via	O
the	O
OS	O
X	O
System	B-Operating_System
Preferences	I-Operating_System
Energy	B-Operating_System
Saver	I-Operating_System
panel	O
,	O
in	O
the	O
Options	O
tab	O
.	O
</s>
<s>
Marking	O
the	O
Wake	O
for	O
network	O
access	O
checkbox	O
enables	O
Wake-on-LAN	B-Protocol
.	O
</s>
<s>
Apple	O
's	O
Apple	B-Operating_System
Remote	I-Operating_System
Desktop	I-Operating_System
client	O
management	O
system	O
can	O
be	O
used	O
to	O
send	O
Wake-on-LAN	B-Protocol
packets	O
,	O
but	O
there	O
are	O
also	O
freeware	O
and	O
shareware	O
Mac	B-Device
OS	I-Device
X	I-Device
applications	O
available	O
.	O
</s>
<s>
On	O
Mac	B-Device
OS	I-Device
X	I-Device
Snow	I-Device
Leopard	I-Device
and	O
later	O
,	O
the	O
service	O
is	O
called	O
Wake	B-Protocol
on	I-Protocol
Demand	I-Protocol
or	O
Bonjour	B-Protocol
Sleep	I-Protocol
Proxy	I-Protocol
and	O
is	O
synonymous	O
with	O
the	O
Sleep	B-Protocol
Proxy	I-Protocol
Service	I-Protocol
.	O
</s>
<s>
It	O
comes	O
enabled	O
out	O
of	O
the	O
box	O
,	O
but	O
in	O
previous	O
versions	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
the	O
service	O
needs	O
to	O
be	O
enabled	O
under	O
the	O
Energy	B-Operating_System
Saver	I-Operating_System
pane	O
of	O
System	B-Operating_System
Preferences	I-Operating_System
.	O
</s>
<s>
The	O
network	B-Protocol
interface	I-Protocol
card	I-Protocol
may	O
allow	O
the	O
service	O
to	O
function	O
only	O
on	O
Wi‑Fi	O
,	O
only	O
on	O
Ethernet	O
,	O
or	O
both	O
.	O
</s>
<s>
Wake-on-LAN	B-Protocol
support	O
may	O
be	O
changed	O
using	O
a	O
subfunction	O
of	O
the	O
ethtool	B-Application
command	O
.	O
</s>
<s>
In	O
the	O
early	O
days	O
of	O
Wake-on-LAN	B-Protocol
the	O
situation	O
was	O
relatively	O
simple	O
:	O
a	O
machine	O
was	O
connected	O
to	O
power	O
but	O
switched	O
off	O
,	O
and	O
it	O
was	O
arranged	O
that	O
a	O
special	O
packet	O
be	O
sent	O
to	O
switch	O
the	O
machine	O
on	O
.	O
</s>
<s>
In	O
some	O
reduced-power	O
modes	O
the	O
system	O
state	O
is	O
stored	O
in	O
RAM	O
and	O
the	O
machine	O
can	O
wake	O
up	O
very	O
quickly	O
;	O
in	O
others	O
the	O
state	O
is	O
saved	O
to	O
disk	O
and	O
the	O
motherboard	B-Device
powered	O
down	O
,	O
taking	O
at	O
least	O
several	O
seconds	O
to	O
wake	O
up	O
.	O
</s>
<s>
The	O
machine	O
's	O
BIOS/UEFI	O
must	O
be	O
set	O
to	O
allow	O
Wake-on-LAN	B-Protocol
.	O
</s>
<s>
Details	O
for	O
any	O
particular	O
motherboard	B-Device
and	O
network	B-Protocol
adapter	I-Protocol
are	O
to	O
be	O
found	O
in	O
the	O
relevant	O
manuals	O
;	O
there	O
is	O
no	O
general	O
method	O
.	O
</s>
<s>
For	O
a	O
machine	O
which	O
is	O
normally	O
unattended	O
,	O
precautions	O
need	O
to	O
be	O
taken	O
to	O
make	O
the	O
Wake-on-LAN	B-Protocol
function	O
as	O
reliable	O
as	O
possible	O
.	O
</s>
<s>
For	O
a	O
machine	O
procured	O
to	O
work	O
in	O
this	O
way	O
,	O
Wake-on-LAN	B-Protocol
functionality	O
is	O
an	O
important	O
part	O
of	O
the	O
purchase	O
procedure	O
.	O
</s>
<s>
Some	O
machines	O
do	O
not	O
support	O
Wake-on-LAN	B-Protocol
after	O
they	O
have	O
been	O
disconnected	O
from	O
power	O
(	O
e.g.	O
,	O
when	O
power	O
is	O
restored	O
after	O
a	O
power	O
failure	O
)	O
.	O
</s>
<s>
If	O
a	O
machine	O
that	O
is	O
not	O
designed	O
to	O
support	O
Wake-on-LAN	B-Protocol
is	O
left	O
powered	O
down	O
after	O
power	O
failure	O
,	O
it	O
may	O
be	O
possible	O
to	O
set	O
the	O
BIOS/UEFI	O
to	O
start	O
it	O
up	O
automatically	O
on	O
restoration	O
of	O
power	O
,	O
so	O
that	O
it	O
is	O
never	O
left	O
in	O
an	O
unresponsive	O
state	O
.	O
</s>
<s>
A	O
typical	O
BIOS/UEFI	O
setting	O
is	O
AC	O
back	O
function	O
which	O
may	O
be	O
on	O
,	O
off	O
,	O
or	O
memory	O
.	O
</s>
<s>
Other	O
problems	O
can	O
affect	O
the	O
ability	O
to	O
start	O
or	O
control	O
the	O
machine	O
remotely	O
:	O
hardware	O
failure	O
of	O
the	O
machine	O
or	O
network	O
,	O
failure	O
of	O
the	O
BIOS/UEFI	O
settings	O
battery	O
(	O
the	O
machine	O
will	O
halt	O
when	O
started	O
before	O
the	O
network	O
connection	O
is	O
made	O
,	O
displaying	O
an	O
error	O
message	O
and	O
requiring	O
a	O
keypress	O
)	O
,	O
loss	O
of	O
control	O
of	O
the	O
machine	O
due	O
to	O
software	O
problems	O
(	O
machine	O
hang	O
,	O
termination	O
of	O
remote	O
control	O
or	O
networking	B-Architecture
software	I-Architecture
,	O
etc	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
use	O
of	O
a	O
reliable	O
server-class	O
machine	O
with	O
RAID	B-Architecture
drives	O
,	O
redundant	O
power	O
supplies	O
,	O
etc.	O
,	O
will	O
help	O
to	O
maximize	O
availability	O
.	O
</s>
<s>
The	O
originator	O
of	O
the	O
wakeup	O
signal	O
(	O
magic	O
packet	O
)	O
does	O
not	O
have	O
to	O
be	O
on	O
the	O
same	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
(	O
LAN	B-General_Concept
)	O
as	O
the	O
computer	O
being	O
woken	O
.	O
</s>
<s>
A	O
virtual	B-Application
private	I-Application
network	I-Application
(	O
VPN	B-Application
)	O
which	O
makes	O
the	O
originator	O
appear	O
to	O
be	O
a	O
member	O
of	O
the	O
LAN	B-General_Concept
.	O
</s>
<s>
The	O
Internet	O
with	O
local	O
broadcastingsome	O
routers	B-Protocol
permit	O
a	O
packet	O
received	O
from	O
the	O
Internet	O
to	O
be	O
broadcast	B-Operating_System
to	O
the	O
entire	O
LAN	B-General_Concept
;	O
the	O
default	O
TCP	B-Protocol
or	O
UDP	B-Protocol
ports	I-Protocol
preconfigured	O
to	O
relay	O
WoL	O
requests	O
are	O
usually	O
ports	O
7	O
(	O
Echo	B-Protocol
Protocol	I-Protocol
)	O
,	O
9	O
(	O
Discard	B-Protocol
Protocol	I-Protocol
)	O
,	O
or	O
both	O
.	O
</s>
<s>
This	O
proxy	O
setting	O
must	O
be	O
enabled	O
in	O
the	O
router	B-Protocol
,	O
and	O
port	B-Protocol
forwarding	O
rules	O
may	O
need	O
to	O
be	O
configured	O
in	O
its	O
embedded	O
firewall	B-Application
in	O
order	O
to	O
accept	O
magic	O
packets	O
coming	O
from	O
the	O
internet	O
side	O
to	O
these	O
restricted	O
port	B-Protocol
numbers	I-Protocol
,	O
and	O
to	O
allow	O
rebroadcasting	O
them	O
on	O
the	O
local	B-General_Concept
network	I-General_Concept
(	O
normally	O
to	O
the	O
same	O
ports	O
and	O
the	O
same	O
TCP	B-Protocol
or	O
UDP	B-Protocol
protocol	I-Protocol
)	O
.	O
</s>
<s>
Such	O
routers	B-Protocol
may	O
also	O
be	O
configurable	O
to	O
use	O
different	O
port	B-Protocol
numbers	I-Protocol
for	O
this	O
proxying	O
service	O
.	O
</s>
<s>
The	O
Internet	O
without	O
local	O
broadcastingif	O
(	O
as	O
often	O
)	O
the	O
firewall	B-Application
or	O
router	B-Protocol
at	O
the	O
destination	O
does	O
not	O
permit	O
packets	O
received	O
from	O
the	O
Internet	O
to	O
be	O
broadcast	B-Operating_System
to	O
the	O
local	B-General_Concept
network	I-General_Concept
,	O
Wake-on-Internet	O
may	O
still	O
be	O
achieved	O
by	O
sending	O
the	O
magic	O
packet	O
to	O
any	O
specified	O
port	B-Protocol
of	O
the	O
destination	O
's	O
Internet	O
address	O
,	O
having	O
previously	O
set	O
the	O
firewall	B-Application
or	O
router	B-Protocol
to	O
forward	O
packets	O
arriving	O
at	O
that	O
port	B-Protocol
to	O
the	O
local	O
IP	O
address	O
of	O
the	O
computer	O
being	O
woken	O
.	O
</s>
<s>
The	O
router	B-Protocol
may	O
require	O
reservation	O
of	O
the	O
local	O
IP	O
address	O
of	O
the	O
computer	O
being	O
woken	O
in	O
order	O
to	O
forward	O
packets	O
to	O
it	O
when	O
it	O
is	O
not	O
live	O
.	O
</s>
