<s>
In	O
computing	O
,	O
the	O
Preboot	B-Device
eXecution	I-Device
Environment	I-Device
,	O
PXE	O
(	O
most	O
often	O
pronounced	O
as	O
pixie	O
,	O
often	O
called	O
PXE	O
Boot/pixie	O
boot	B-Operating_System
.	O
)	O
</s>
<s>
specification	O
describes	O
a	O
standardized	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
environment	O
that	O
boots	B-Operating_System
a	O
software	O
assembly	O
,	O
retrieved	O
from	O
a	O
network	O
,	O
on	O
PXE-enabled	O
clients	O
.	O
</s>
<s>
On	O
the	O
client	B-Protocol
side	O
it	O
requires	O
only	O
a	O
PXE-capable	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
(	O
NIC	O
)	O
,	O
and	O
uses	O
a	O
small	O
set	O
of	O
industry-standard	O
network	O
protocols	O
such	O
as	O
DHCP	B-Protocol
and	O
TFTP	B-Device
.	O
</s>
<s>
The	O
concept	O
behind	O
the	O
PXE	O
originated	O
in	O
the	O
early	O
days	O
of	O
protocols	O
like	O
BOOTP/DHCP/TFTP	O
,	O
and	O
it	O
forms	O
part	O
of	O
the	O
Unified	B-Architecture
Extensible	I-Architecture
Firmware	I-Architecture
Interface	I-Architecture
(	O
UEFI	B-Architecture
)	O
standard	O
.	O
</s>
<s>
In	O
modern	O
data	O
centers	O
,	O
PXE	O
is	O
the	O
most	O
frequent	O
choice	O
for	O
operating	O
system	O
booting	B-Operating_System
,	O
installation	O
and	O
deployment	O
.	O
</s>
<s>
Since	O
the	O
beginning	O
of	O
computer	O
networks	O
,	O
there	O
has	O
been	O
a	O
persistent	O
need	O
for	O
client	B-Protocol
systems	O
which	O
can	O
boot	B-Operating_System
appropriate	O
software	O
images	O
,	O
with	O
appropriate	O
configuration	O
parameters	O
,	O
both	O
retrieved	O
at	O
boot	B-Operating_System
time	I-Operating_System
from	O
one	O
or	O
more	O
network	B-Application
servers	I-Application
.	O
</s>
<s>
This	O
goal	O
requires	O
a	O
client	B-Protocol
to	O
use	O
a	O
set	O
of	O
pre-boot	O
services	O
,	O
based	O
on	O
industry	O
standard	O
network	O
protocols	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
Network	O
Bootstrap	B-Operating_System
Program	I-Operating_System
(	O
NBP	O
)	O
which	O
is	O
initially	O
downloaded	O
and	O
run	O
must	O
be	O
built	O
using	O
a	O
client	B-Protocol
firmware	B-Application
layer	O
(	O
at	O
the	O
device	O
to	O
be	O
bootstrapped	O
via	O
PXE	O
)	O
providing	O
a	O
hardware	O
independent	O
standardized	O
way	O
to	O
interact	O
with	O
the	O
surrounding	O
network	B-Device
booting	I-Device
environment	O
.	O
</s>
<s>
In	O
this	O
case	O
the	O
availability	O
and	O
subjection	O
to	O
standards	O
are	O
a	O
key	O
factor	O
required	O
to	O
guarantee	O
the	O
network	B-Device
boot	I-Device
process	O
system	O
interoperability	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
attempts	O
in	O
this	O
regard	O
was	O
bootstrap	O
loading	O
using	O
TFTP	B-Device
standard	O
RFC	O
906	O
,	O
published	O
in	O
1984	O
,	O
which	O
established	O
the	O
1981	O
published	O
Trivial	B-Device
File	I-Device
Transfer	I-Device
Protocol	I-Device
(	O
TFTP	B-Device
)	O
standard	O
RFC	O
783	O
to	O
be	O
used	O
as	O
the	O
standard	O
file	O
transfer	O
protocol	O
for	O
bootstrap	O
loading	O
.	O
</s>
<s>
It	O
was	O
followed	O
shortly	O
after	O
by	O
the	O
Bootstrap	B-Device
Protocol	I-Device
standard	O
RFC	O
951	O
(	O
BOOTP	B-Device
)	O
,	O
published	O
in	O
1985	O
,	O
which	O
allowed	O
a	O
disk-less	O
client	B-Protocol
machine	I-Protocol
to	O
discover	O
its	O
own	O
IP	B-Protocol
address	O
,	O
the	O
address	O
of	O
a	O
TFTP	B-Device
server	O
,	O
and	O
the	O
name	O
of	O
an	O
NBP	O
to	O
be	O
loaded	O
into	O
memory	O
and	O
executed	O
.	O
</s>
<s>
BOOTP	B-Device
implementation	O
difficulties	O
,	O
among	O
other	O
reasons	O
,	O
eventually	O
led	O
to	O
the	O
development	O
of	O
the	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
standard	O
RFC	O
2131	O
(	O
DHCP	B-Protocol
)	O
published	O
in	O
1997	O
.	O
</s>
<s>
The	O
pioneering	O
TFTP/BOOTP/DHCP	O
approach	O
fell	O
short	O
,	O
as	O
at	O
the	O
time	O
,	O
it	O
did	O
not	O
define	O
the	O
required	O
standardized	O
client	B-Protocol
side	O
of	O
the	O
provisioning	O
environment	O
.	O
</s>
<s>
The	O
Preboot	B-Device
Execution	I-Device
Environment	I-Device
(	O
PXE	O
)	O
was	O
introduced	O
as	O
part	O
of	O
the	O
Wired	B-Application
for	I-Application
Management	I-Application
framework	O
by	O
Intel	O
and	O
is	O
described	O
in	O
the	O
specification	O
published	O
by	O
Intel	O
and	O
SystemSoft	O
.	O
</s>
<s>
The	O
PXE	O
environment	O
makes	O
use	O
of	O
several	O
standard	O
client‑server	O
protocols	O
including	O
DHCP	B-Protocol
and	O
TFTP	B-Device
(	O
now	O
defined	O
by	O
the	O
1992	O
published	O
RFC	O
1350	O
)	O
.	O
</s>
<s>
Within	O
the	O
PXE	O
schema	O
the	O
client	B-Protocol
side	O
of	O
the	O
provisioning	O
equation	O
is	O
an	O
integral	O
part	O
of	O
the	O
PXE	O
standard	O
and	O
it	O
is	O
implemented	O
either	O
as	O
a	O
Network	B-Protocol
Interface	I-Protocol
Card	I-Protocol
(	O
NIC	O
)	O
BIOS	B-Device
extension	I-Device
or	O
current	O
devices	O
in	O
UEFI	B-Architecture
code	O
.	O
</s>
<s>
This	O
distinctive	O
firmware	B-Application
layer	O
makes	O
available	O
at	O
the	O
client	B-Protocol
the	O
functions	O
of	O
a	O
basic	O
Universal	B-Device
Network	I-Device
Device	I-Device
Interface	I-Device
(	O
UNDI	B-Device
)	O
,	O
a	O
minimalistic	O
UDP/IP	B-Protocol
stack	O
,	O
a	O
Preboot	O
(	O
DHCP	B-Protocol
)	O
client	B-Protocol
module	O
and	O
a	O
TFTP	B-Device
client	B-Protocol
module	O
,	O
together	O
forming	O
the	O
PXE	O
application	B-Application
programming	I-Application
interfaces	I-Application
(	O
APIs	B-Application
)	O
used	O
by	O
the	O
NBP	O
when	O
needing	O
to	O
interact	O
with	O
the	O
services	O
offered	O
by	O
the	O
server	O
counterpart	O
of	O
the	O
PXE	O
environment	O
.	O
</s>
<s>
TFTP	B-Device
's	O
low	O
throughput	O
,	O
especially	O
when	O
used	O
over	O
high-latency	O
links	O
,	O
has	O
been	O
initially	O
mitigated	O
by	O
the	O
TFTP	B-Device
Blocksize	O
Option	O
RFC	O
2348	O
published	O
in	O
May	O
1998	O
,	O
and	O
later	O
by	O
the	O
TFTP	B-Device
Windowsize	O
Option	O
RFC	O
7440	O
published	O
in	O
January	O
2015	O
,	O
allowing	O
potentially	O
larger	O
payload	O
deliveries	O
and	O
thus	O
improving	O
throughput	O
.	O
</s>
<s>
The	O
PXE	O
environment	O
relies	O
on	O
a	O
combination	O
of	O
industry-standard	O
Internet	B-Protocol
protocols	I-Protocol
,	O
namely	O
UDP/IP	B-Protocol
,	O
DHCP	B-Protocol
and	O
TFTP	B-Device
.	O
</s>
<s>
These	O
protocols	O
have	O
been	O
selected	O
because	O
they	O
are	O
easily	O
implemented	O
in	O
the	O
client	B-Protocol
's	O
NIC	O
firmware	B-Application
,	O
resulting	O
in	O
standardized	O
small-footprint	O
PXE	O
ROMs	O
.	O
</s>
<s>
Standardization	O
,	O
small	O
size	O
of	O
PXE	O
firmware	B-Application
images	O
and	O
their	O
low	O
use	O
of	O
resources	O
are	O
some	O
of	O
the	O
primary	O
design	O
goals	O
,	O
allowing	O
the	O
client	B-Protocol
side	O
of	O
the	O
PXE	O
standard	O
to	O
be	O
identically	O
implemented	O
on	O
a	O
wide	O
variety	O
of	O
systems	O
,	O
ranging	O
from	O
powerful	O
client	B-Protocol
computers	I-Protocol
to	O
resource-limited	O
single-board	B-Device
computers	I-Device
(	O
SBC	O
)	O
and	O
system-on-a-chip	B-Architecture
(	O
SoC	O
)	O
computers	O
.	O
</s>
<s>
DHCP	B-Protocol
is	O
used	O
to	O
provide	O
the	O
appropriate	O
client	B-Protocol
network	O
parameters	O
and	O
specifically	O
the	O
location	O
(	O
IP	B-Protocol
address	O
)	O
of	O
the	O
TFTP	B-Device
server	O
hosting	O
,	O
ready	O
for	O
download	O
,	O
the	O
initial	O
bootstrap	B-Operating_System
program	I-Operating_System
(	O
NBP	O
)	O
and	O
complementary	O
files	O
.	O
</s>
<s>
To	O
initiate	O
a	O
PXE	O
bootstrap	O
session	O
the	O
DHCP	B-Protocol
component	O
of	O
the	O
client	B-Protocol
's	O
PXE	O
firmware	B-Application
broadcasts	B-Protocol
a	O
DHCPDISCOVER	O
packet	O
containing	O
PXE-specific	O
options	O
to	O
port	O
67/UDP	O
(	O
DHCP	B-Protocol
server	I-Protocol
port	O
)	O
;	O
it	O
asks	O
for	O
the	O
required	O
network	O
configuration	O
and	O
network	B-Device
booting	I-Device
parameters	O
.	O
</s>
<s>
The	O
PXE-specific	O
options	O
identify	O
the	O
initiated	O
DHCP	B-Protocol
transaction	O
as	O
a	O
PXE	O
transaction	O
.	O
</s>
<s>
Standard	O
DHCP	B-Protocol
servers	I-Protocol
(	O
non	O
PXE	O
enabled	O
)	O
will	O
be	O
able	O
to	O
answer	O
with	O
a	O
regular	O
DHCPOFFER	O
carrying	O
networking	O
information	O
(	O
i.e.	O
</s>
<s>
IP	B-Protocol
address	O
)	O
but	O
not	O
the	O
PXE	O
specific	O
parameters	O
.	O
</s>
<s>
A	O
PXE	O
client	B-Protocol
will	O
not	O
be	O
able	O
to	O
boot	B-Operating_System
if	O
it	O
only	O
receives	O
an	O
answer	O
from	O
a	O
non	O
PXE	O
enabled	O
DHCP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
After	O
parsing	O
a	O
PXE	O
enabled	O
DHCP	B-Protocol
server	I-Protocol
DHCPOFFER	O
,	O
the	O
client	B-Protocol
will	O
be	O
able	O
to	O
set	O
its	O
own	O
network	O
IP	B-Protocol
address	O
,	O
IP	B-Protocol
Mask	O
,	O
etc.	O
,	O
and	O
to	O
point	O
to	O
the	O
network	O
located	O
booting	B-Operating_System
resources	O
,	O
based	O
on	O
the	O
received	O
TFTP	B-Device
Server	O
IP	B-Protocol
address	O
and	O
the	O
name	O
of	O
the	O
NBP	O
.	O
</s>
<s>
The	O
client	B-Protocol
next	O
transfers	O
the	O
NBP	O
into	O
its	O
own	O
random-access	B-Architecture
memory	I-Architecture
(	O
RAM	B-Architecture
)	O
using	O
TFTP	B-Device
,	O
possibly	O
verifies	O
it	O
(	O
i.e.	O
</s>
<s>
UEFI	B-Architecture
Secure	O
Boot	B-Operating_System
)	O
,	O
and	O
finally	O
boots	B-Operating_System
from	O
it	O
.	O
</s>
<s>
NBPs	O
are	O
just	O
the	O
first	O
link	O
in	O
the	O
boot	B-Operating_System
chain	O
process	O
and	O
they	O
generally	O
request	O
via	O
TFTP	B-Device
a	O
small	O
set	O
of	O
complementary	O
files	O
in	O
order	O
to	O
get	O
running	O
a	O
minimalistic	O
OS	O
executive	O
(	O
i.e.	O
</s>
<s>
WindowsPE	O
,	O
or	O
a	O
basic	O
Linux	O
kernel+initrd	O
)	O
.	O
</s>
<s>
The	O
small	O
OS	O
executive	O
loads	O
its	O
own	O
network	O
drivers	O
and	O
TCP/IP	B-Protocol
stack	I-Protocol
.	O
</s>
<s>
At	O
this	O
point	O
,	O
the	O
remaining	O
instructions	O
required	O
to	O
boot	B-Operating_System
or	O
install	O
a	O
full	O
OS	O
are	O
provided	O
not	O
over	O
TFTP	B-Device
,	O
but	O
using	O
a	O
robust	O
transfer	O
protocol	O
(	O
such	O
as	O
HTTP	B-Protocol
,	O
CIFS	B-Operating_System
,	O
or	O
NFS	B-Protocol
)	O
.	O
</s>
<s>
The	O
PXE	O
Client/Server	B-Operating_System
environment	I-Operating_System
was	O
designed	O
so	O
it	O
can	O
be	O
seamlessly	O
integrated	O
with	O
an	O
already	O
in	O
place	O
DHCP	B-Protocol
and	O
TFTP	B-Device
server	O
infrastructure	O
.	O
</s>
<s>
This	O
design	O
goal	O
presented	O
a	O
challenge	O
when	O
dealing	O
with	O
the	O
classic	O
DHCP	B-Protocol
protocol	O
.	O
</s>
<s>
Corporate	O
DHCP	B-Protocol
servers	I-Protocol
are	O
usually	O
subject	O
to	O
strict	O
policies	O
that	O
are	O
designed	O
to	O
prevent	O
easily	O
adding	O
the	O
additional	O
parameters	O
and	O
rules	O
required	O
to	O
support	O
a	O
PXE	O
environment	O
.	O
</s>
<s>
For	O
this	O
reason	O
the	O
PXE	O
standard	O
developed	O
the	O
concept	O
of	O
DHCP	B-Protocol
redirection	O
or	O
"	O
proxyDHCP	O
"	O
.	O
</s>
<s>
The	O
idea	O
behind	O
a	O
proxyDHCP	O
is	O
to	O
split	O
the	O
PXE	O
DHCP	B-Protocol
requirements	O
in	O
two	O
independently	O
run	O
and	O
administered	O
server	O
units	O
:	O
</s>
<s>
The	O
classic	O
DHCP	B-Protocol
server	I-Protocol
providing	O
IP	B-Protocol
address	O
,	O
IP	B-Protocol
mask	O
,	O
etc	O
.	O
</s>
<s>
to	O
all	O
booting	B-Operating_System
DHCP	B-Protocol
clients	O
.	O
</s>
<s>
The	O
proxyDHCP	O
server	O
providing	O
TFTP	B-Device
server	O
IP	B-Protocol
address	O
and	O
name	O
of	O
the	O
NBP	O
only	O
to	O
PXE	O
identified	O
booting	B-Operating_System
clients	O
.	O
</s>
<s>
In	O
a	O
DHCP	B-Protocol
plus	O
proxyDHCP	O
server	O
environment	O
the	O
PXE	O
client	B-Protocol
initially	O
broadcasts	B-Protocol
a	O
single	O
PXE	O
DHCPDISCOVER	O
packet	O
and	O
receives	O
two	O
complementary	O
DHCPOFFERs	O
;	O
one	O
from	O
the	O
regular	O
non	O
PXE	O
enabled	O
DHCP	B-Protocol
server	I-Protocol
and	O
a	O
second	O
one	O
from	O
the	O
proxyDHCP	O
server	O
.	O
</s>
<s>
Both	O
answers	O
together	O
provide	O
the	O
required	O
information	O
to	O
allow	O
the	O
PXE	O
client	B-Protocol
to	O
continue	O
with	O
its	O
booting	B-Operating_System
process	O
.	O
</s>
<s>
This	O
non-intrusive	O
approach	O
allows	O
setting	O
a	O
PXE	O
environment	O
without	O
touching	O
the	O
configuration	O
of	O
an	O
already	O
working	O
DHCP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
The	O
proxyDHCP	O
service	O
may	O
also	O
run	O
on	O
the	O
same	O
host	O
as	O
the	O
standard	O
DHCP	B-Protocol
service	O
but	O
even	O
in	O
this	O
case	O
they	O
are	O
both	O
two	O
independently	O
run	O
and	O
administered	O
applications	O
.	O
</s>
<s>
Since	O
two	O
services	O
cannot	O
use	O
the	O
same	O
port	O
67/UDP	O
on	O
the	O
same	O
host	O
,	O
the	O
proxyDHCP	O
runs	O
on	O
port	O
4011/UDP	O
.	O
</s>
<s>
The	O
version	O
2.1	O
of	O
the	O
specification	O
defined	O
architecture	O
identifiers	O
for	O
six	O
system	O
types	O
,	O
including	O
IA-64	B-General_Concept
and	O
DEC	B-Device
Alpha	I-Device
.	O
</s>
<s>
However	O
,	O
PXE	O
v2.1	O
only	O
completely	O
covered	O
IA-32	B-Device
.	O
</s>
<s>
Despite	O
this	O
apparent	O
lack	O
of	O
completeness	O
Intel	O
has	O
recently	O
decided	O
to	O
widely	O
support	O
PXE	O
within	O
the	O
new	O
UEFI	B-Architecture
specification	O
extending	O
the	O
PXE	O
functionality	O
to	O
all	O
EFI/UEFI	O
environments	O
.	O
</s>
<s>
while	O
executing	O
in	O
the	O
UEFI	B-Architecture
boot	B-Operating_System
services	O
environment	O
.	O
</s>
<s>
These	O
protocols	O
include	O
the	O
Simple	O
Network	O
Protocol	O
(	O
SNP	O
)	O
,	O
the	O
PXE	O
Base	O
Code	O
Protocol	O
(	O
PXE	O
)	O
,	O
and	O
the	O
Boot	B-Operating_System
Integrity	O
Services	O
Protocol	O
(	O
BIS	O
)	O
.	O
</s>
<s>
Today	O
in	O
a	O
PXE	O
environment	O
the	O
client	B-Protocol
architecture	O
detection	O
is	O
rarely	O
based	O
on	O
the	O
identifiers	O
originally	O
included	O
with	O
the	O
PXE	O
v2.1	O
specification	O
,	O
instead	O
each	O
computer	O
that	O
will	O
be	O
booting	B-Operating_System
from	O
the	O
network	O
should	O
have	O
set	O
DHCP	B-Protocol
option	O
93	O
to	O
indicate	O
the	O
client	B-Protocol
's	O
architecture	O
.	O
</s>
<s>
This	O
enables	O
a	O
PXE	O
server	O
to	O
know	O
(	O
at	O
boot	B-Operating_System
time	I-Operating_System
)	O
the	O
exact	O
architecture	O
of	O
the	O
client	B-Protocol
from	O
the	O
first	O
network	B-Device
boot	I-Device
packet	O
.	O
</s>
<s>
The	O
client	B-Protocol
system	O
architecture	O
values	O
are	O
listed	O
(	O
among	O
other	O
PXE	O
parameters	O
)	O
within	O
the	O
2006	O
published	O
RFC	O
4578	O
(	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
(	O
DHCP	B-Protocol
)	O
Options	O
for	O
the	O
Intel	O
Preboot	B-Device
eXecution	I-Device
Environment	I-Device
(	O
PXE	O
)	O
)	O
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
IPv6	B-Protocol
DHCP	B-Protocol
has	O
evolved	O
into	O
DHCPv6	B-Protocol
;	O
the	O
need	O
for	O
options	O
supporting	O
PXE	O
within	O
the	O
new	O
DHCP	B-Protocol
protocol	O
has	O
been	O
addressed	O
by	O
the	O
2010	O
published	O
RFC	O
5970	O
(	O
DHCPv6	B-Protocol
Options	O
for	O
Network	B-Device
Boot	I-Device
)	O
.	O
</s>
<s>
The	O
original	O
PXE	O
client	B-Protocol
firmware	B-Application
extension	O
was	O
designed	O
as	O
an	O
Option	B-Device
ROM	I-Device
for	O
the	O
IA-32	B-Device
BIOS	B-Operating_System
,	O
so	O
a	O
personal	B-Device
computer	I-Device
(	O
PC	O
)	O
was	O
originally	O
made	O
PXE-capable	O
by	O
installing	O
a	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
(	O
NIC	O
)	O
that	O
provided	O
a	O
PXE	O
Option	B-Device
ROM	I-Device
.	O
</s>
<s>
Today	O
the	O
client	B-Protocol
PXE	O
code	O
is	O
directly	O
included	O
within	O
the	O
NIC	O
's	O
own	O
firmware	B-Application
or	O
as	O
part	O
of	O
the	O
UEFI	B-Architecture
firmware	I-Architecture
on	O
the	O
motherboard	O
.	O
</s>
<s>
Even	O
when	O
the	O
original	O
client	B-Protocol
PXE	O
firmware	B-Application
has	O
been	O
written	O
by	O
Intel	O
and	O
always	O
provided	O
at	O
no	O
cost	O
as	O
a	O
linkable	O
IA32	B-Device
object	B-Application
code	I-Application
format	I-Application
module	O
included	O
in	O
their	O
Product	O
Development	O
Kit	O
(	O
PDK	O
)	O
,	O
the	O
open	O
source	O
world	O
has	O
produced	O
over	O
the	O
years	O
non-standard	O
derivative	O
projects	O
like	O
gPXE/iPXE	O
offering	O
their	O
own	O
ROMs	O
.	O
</s>
<s>
While	O
Intel	O
based	O
ROMs	O
have	O
been	O
implementing	O
the	O
client	B-Protocol
side	O
of	O
the	O
PXE	O
standard	O
for	O
more	O
than	O
20	O
year	O
some	O
users	O
were	O
willing	O
to	O
trade	O
extra	O
features	O
for	O
stability	O
and	O
PXE	O
standard	O
conformance	O
.	O
</s>
<s>
PXE	O
acceptance	O
since	O
v2.1	O
has	O
been	O
ubiquitous	O
;	O
today	O
it	O
is	O
virtually	O
impossible	O
to	O
find	O
a	O
network	B-Protocol
card	I-Protocol
without	O
PXE	O
firmware	B-Application
on	O
it	O
.	O
</s>
<s>
The	O
availability	O
of	O
inexpensive	O
Gigabit	O
Ethernet	O
hardware	O
(	O
NICs	O
,	O
switches	B-Protocol
,	O
routers	B-Protocol
,	O
etc	O
.	O
)	O
</s>
<s>
has	O
made	O
PXE	O
the	O
fastest	O
method	O
available	O
for	O
installing	O
an	O
operating	O
system	O
on	O
a	O
client	B-Protocol
when	O
competing	O
against	O
the	O
classic	O
CD	B-Device
,	O
DVD	O
,	O
and	O
USB	O
flash	O
drive	O
alternatives	O
.	O
</s>
<s>
All	O
the	O
major	O
Linux	B-Operating_System
distributions	O
.	O
</s>
<s>
HP	O
OpenVMS	B-Operating_System
on	O
Itanium	B-General_Concept
hardware	O
.	O
</s>
<s>
In	O
regard	O
to	O
NBP	O
development	O
there	O
are	O
several	O
projects	O
implementing	O
Boot	B-Operating_System
Managers	O
able	O
to	O
offer	O
boot	B-Operating_System
menu	I-Operating_System
extended	O
features	O
,	O
scripting	O
capabilities	O
,	O
etc	O
.	O
</s>
<s>
All	O
the	O
above-mentioned	O
projects	O
,	O
when	O
they	O
are	O
able	O
to	O
boot/install	O
more	O
than	O
one	O
OS	O
,	O
work	O
under	O
a	O
"	O
Boot	B-Operating_System
Manager	O
-	O
Boot	B-Operating_System
Loader	O
"	O
paradigm	O
.	O
</s>
<s>
The	O
initial	O
NBP	O
is	O
a	O
Boot	B-Operating_System
Manager	O
able	O
to	O
retrieve	O
its	O
own	O
configuration	O
and	O
deploy	O
a	O
menu	O
of	O
booting	B-Operating_System
options	O
.	O
</s>
<s>
The	O
user	O
selects	O
a	O
booting	B-Operating_System
option	O
and	O
an	O
OS	O
dependent	O
Boot	B-Operating_System
Loader	O
is	O
downloaded	O
and	O
run	O
in	O
order	O
to	O
continue	O
with	O
the	O
selected	O
specific	O
booting	B-Operating_System
procedure	O
.	O
</s>
<s>
Apple	O
has	O
come	O
up	O
with	O
a	O
very	O
similar	O
network	B-Device
boot	I-Device
approach	O
under	O
the	O
umbrella	O
of	O
the	O
Boot	B-Device
Server	I-Device
Discovery	I-Device
Protocol	I-Device
(	O
BSDP	B-Device
)	O
specification	O
.	O
</s>
<s>
BSDP	B-Device
v0.1	O
was	O
initially	O
published	O
by	O
Apple	O
in	O
August	O
1999	O
and	O
its	O
last	O
v1.0.8	O
was	O
published	O
in	O
September	O
2010	O
.	O
</s>
<s>
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Server	I-Operating_System
included	O
a	O
system	O
tool	O
called	O
NetBoot	B-Device
.	O
</s>
<s>
A	O
NetBoot	B-Device
client	B-Protocol
uses	O
BSDP	B-Device
to	O
dynamically	O
acquire	O
resources	O
that	O
enable	O
it	O
to	O
boot	B-Operating_System
a	O
suitable	O
operating	O
system	O
.	O
</s>
<s>
BSDP	B-Device
is	O
crafted	O
on	O
top	O
of	O
DHCP	B-Protocol
using	O
vendor-specific	O
information	O
to	O
provide	O
the	O
additional	O
NetBoot	B-Device
functionality	O
not	O
present	O
in	O
standard	O
DHCP	B-Protocol
.	O
</s>
<s>
The	O
protocol	O
is	O
implemented	O
in	O
client	B-Protocol
firmware	B-Application
.	O
</s>
<s>
At	O
boot	B-Operating_System
time	I-Operating_System
,	O
the	O
client	B-Protocol
obtains	O
an	O
IP	B-Protocol
address	O
via	O
DHCP	B-Protocol
then	O
discovers	O
boot	B-Operating_System
servers	B-Application
using	O
BSDP	B-Device
.	O
</s>
<s>
Each	O
BSDP	B-Device
server	O
responds	O
with	O
boot	B-Operating_System
information	O
consisting	O
of	O
:	O
</s>
<s>
The	O
client	B-Protocol
chooses	O
an	O
operating	O
system	O
from	O
the	O
list	O
and	O
sends	O
a	O
message	O
to	O
the	O
server	O
indicating	O
its	O
selection	O
.	O
</s>
<s>
boot	B-Operating_System
image	O
,	O
and	O
any	O
other	O
information	O
needed	O
to	O
download	O
and	O
execute	O
the	O
selected	O
operating	O
system	O
.	O
</s>
<s>
Microsoft	O
created	O
a	O
non-overlapping	O
extension	O
of	O
the	O
PXE	O
environment	O
with	O
their	O
Boot	B-Operating_System
Information	O
Negotiation	O
Layer	O
(	O
BINL	O
)	O
.	O
</s>
<s>
It	O
includes	O
certain	O
preparation	O
processes	O
and	O
a	O
network	O
protocol	O
that	O
could	O
be	O
somehow	O
considered	O
a	O
Microsoft-crafted	O
DHCP	B-Protocol
extension	O
.	O
</s>
<s>
BINL	O
is	O
a	O
Microsoft	O
proprietary	O
technology	O
that	O
uses	O
PXE	O
standard	O
client	B-Protocol
firmware	B-Application
.	O
</s>
<s>
RFC	O
#	O
Title	O
Published	O
Author	O
Obsolete	O
and	O
Update	O
InformationThe	O
TFTP	B-Device
Protocol	O
(	O
Revision	O
2	O
)	O
Jun-1981K	O
.	O
</s>
<s>
Sollins	O
Bootstrap	O
Loading	O
using	O
TFTPJun-1984Ross	O
Finlayson	O
Bootstrap	O
ProtocolSep-1985Bill	O
CroftUpdated	O
by	O
RFC	O
1395	O
,	O
RFC	O
1497	O
,	O
RFC	O
1532	O
,	O
RFC	O
1542	O
,	O
RFC	O
5494The	O
TFTP	B-Device
Protocol	O
(	O
Revision	O
2	O
)	O
Jul-1992K	O
.	O
</s>
<s>
Malkin	O
DHCP	B-Protocol
Options	O
for	O
the	O
Intel	O
PXENov-2006M	O
.	O
</s>
<s>
Johnston	O
DHCPv6	B-Protocol
Options	O
for	O
Network	O
BootSep-2010T	O
.	O
</s>
<s>
Huth	O
TFTP	B-Device
Windowsize	O
OptionJan-2015P	O
.	O
</s>
