<s>
The	O
Web	O
Proxy	O
Auto-Discovery	O
(	O
WPAD	B-Protocol
)	O
Protocol	O
is	O
a	O
method	O
used	O
by	O
clients	O
to	O
locate	O
the	O
URL	O
of	O
a	O
configuration	O
file	O
using	O
DHCP	B-Protocol
and/or	O
DNS	B-Protocol
discovery	O
methods	O
.	O
</s>
<s>
The	O
WPAD	B-Protocol
protocol	O
only	O
outlines	O
the	O
mechanism	O
for	O
discovering	O
the	O
location	O
of	O
this	O
file	O
,	O
but	O
the	O
most	O
commonly	O
deployed	O
configuration	O
file	O
format	O
is	O
the	O
proxy	B-Protocol
auto-config	I-Protocol
format	O
originally	O
designed	O
by	O
Netscape	B-Protocol
in	O
1996	O
for	O
Netscape	B-Protocol
Navigator	I-Protocol
2.0	I-Protocol
.	O
</s>
<s>
The	O
WPAD	B-Protocol
protocol	O
was	O
drafted	O
by	O
a	O
consortium	O
of	O
companies	O
including	O
Inktomi	B-Application
Corporation	I-Application
,	O
Microsoft	O
Corporation	O
,	O
RealNetworks	O
,	O
Inc.	O
,	O
and	O
Sun	O
Microsystems	O
,	O
Inc	O
.	O
(	O
now	O
Oracle	B-Application
Corp	I-Application
.	I-Application
)	O
.	O
</s>
<s>
WPAD	B-Protocol
is	O
documented	O
in	O
an	O
INTERNET-DRAFT	O
which	O
expired	O
in	O
December	O
1999	O
.	O
</s>
<s>
However	O
,	O
WPAD	B-Protocol
is	O
still	O
supported	O
by	O
all	O
major	O
browsers	B-Application
.	O
</s>
<s>
WPAD	B-Protocol
was	O
first	O
included	O
with	O
Internet	B-Protocol
Explorer	I-Protocol
5.0	I-Protocol
.	O
</s>
<s>
In	O
order	O
for	O
all	O
browsers	B-Application
in	O
an	O
organization	O
to	O
be	O
supplied	O
the	O
same	O
proxy	O
policy	O
,	O
without	O
configuring	O
each	O
browser	B-Application
manually	O
,	O
both	O
the	O
below	O
technologies	O
are	O
required	O
:	O
</s>
<s>
Proxy	B-Protocol
auto-config	I-Protocol
(	O
PAC	O
)	O
standard	O
:	O
create	O
and	O
publish	O
one	O
central	O
proxy	O
configuration	O
file	O
.	O
</s>
<s>
Web	B-Protocol
Proxy	I-Protocol
Auto-Discovery	I-Protocol
Protocol	I-Protocol
(	O
WPAD	B-Protocol
)	O
standard	O
:	O
ensure	O
that	O
an	O
organization	O
's	O
browsers	B-Application
will	O
find	O
this	O
file	O
without	O
manual	O
configuration	O
.	O
</s>
<s>
The	O
WPAD	B-Protocol
standard	O
defines	O
two	O
alternative	O
methods	O
the	O
system	O
administrator	O
can	O
use	O
to	O
publish	O
the	O
location	O
of	O
the	O
proxy	O
configuration	O
file	O
,	O
using	O
the	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
(	O
DHCP	B-Protocol
)	O
or	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
:	O
</s>
<s>
Before	O
fetching	O
its	O
first	O
page	O
,	O
a	O
web	B-Application
browser	I-Application
implementing	O
this	O
method	O
sends	O
a	O
DHCPINFORM	O
query	O
to	O
the	O
local	O
DHCP	B-Protocol
server	I-Protocol
,	O
and	O
uses	O
the	O
URL	O
from	O
the	O
WPAD	B-Protocol
option	O
in	O
the	O
server	O
's	O
reply	O
.	O
</s>
<s>
If	O
the	O
DHCP	B-Protocol
server	I-Protocol
does	O
not	O
provide	O
the	O
desired	O
information	O
,	O
DNS	B-Protocol
is	O
used	O
.	O
</s>
<s>
If	O
,	O
for	O
example	O
,	O
the	O
network	O
name	O
of	O
the	O
user	O
's	O
computer	O
is	O
pc.department.branch.example.com,	O
the	O
browser	B-Application
will	O
try	O
the	O
following	O
URLs	O
in	O
turn	O
until	O
it	O
finds	O
a	O
proxy	O
configuration	O
file	O
within	O
the	O
domain	O
of	O
the	O
client	O
:	O
</s>
<s>
Additionally	O
on	O
Windows	O
if	O
the	O
DNS	B-Protocol
query	I-Protocol
is	O
unsuccessful	O
then	O
Link-Local	B-Protocol
Multicast	I-Protocol
Name	I-Protocol
Resolution	I-Protocol
(	O
LLMNR	B-Protocol
)	O
and/or	O
NetBIOS	B-Protocol
will	O
be	O
used	O
.	O
</s>
