<s>
DirectAccess	B-Application
,	O
also	O
known	O
as	O
Unified	O
Remote	O
Access	O
,	O
is	O
a	O
VPN	B-Application
technology	O
that	O
provides	O
intranet	B-General_Concept
connectivity	O
to	O
client	O
computers	O
when	O
they	O
are	O
connected	O
to	O
the	O
Internet	O
.	O
</s>
<s>
Unlike	O
many	O
traditional	O
VPN	B-Application
connections	O
,	O
which	O
must	O
be	O
initiated	O
and	O
terminated	O
by	O
explicit	O
user	O
action	O
,	O
DirectAccess	B-Application
connections	O
are	O
designed	O
to	O
connect	O
automatically	O
as	O
soon	O
as	O
the	O
computer	O
connects	O
to	O
the	O
Internet	O
.	O
</s>
<s>
DirectAccess	B-Application
was	O
introduced	O
in	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
,	O
providing	O
this	O
service	O
to	O
Windows	B-Device
7	I-Device
and	O
Windows	B-Application
8	I-Application
"	O
Enterprise	O
"	O
edition	O
clients	O
.	O
</s>
<s>
In	O
2010	O
,	O
Microsoft	B-General_Concept
Forefront	I-General_Concept
Unified	I-General_Concept
Access	I-General_Concept
Gateway	I-General_Concept
(	O
UAG	O
)	O
was	O
released	O
,	O
which	O
simplifies	O
the	O
deployment	O
of	O
DirectAccess	B-Application
for	O
Windows	B-Device
2008	I-Device
R2	I-Device
,	O
and	O
includes	O
additional	O
components	O
that	O
make	O
it	O
easier	O
to	O
integrate	O
without	O
the	O
need	O
to	O
deploy	O
IPv6	B-Protocol
on	O
the	O
network	O
,	O
and	O
with	O
a	O
dedicated	O
user	O
interface	O
for	O
the	O
configuration	O
and	O
monitoring	O
.	O
</s>
<s>
Some	O
requirements	O
and	O
limitations	O
that	O
were	O
part	O
of	O
the	O
design	O
of	O
DirectAccess	B-Application
with	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
and	O
UAG	O
have	O
been	O
changed	O
(	O
see	O
requirements	O
below	O
)	O
.	O
</s>
<s>
While	O
DirectAccess	B-Application
is	O
based	O
on	O
Microsoft	O
technology	O
,	O
third-party	O
solutions	O
exist	O
for	O
accessing	O
internal	O
UNIX	B-Application
and	O
Linux	B-Application
servers	O
through	O
DirectAccess	B-Application
.	O
</s>
<s>
With	O
Windows	B-Device
Server	I-Device
2012	I-Device
,	O
DirectAccess	B-Application
is	O
fully	O
integrated	O
into	O
the	O
operating	O
system	O
,	O
providing	O
a	O
user	O
interface	O
to	O
configure	O
and	O
native	O
IPv6	B-Protocol
and	O
IPv4	B-Protocol
support	O
.	O
</s>
<s>
DirectAccess	B-Application
establishes	O
IPsec	B-Protocol
tunnels	O
from	O
the	O
client	O
to	O
the	O
DirectAccess	B-Application
server	O
,	O
and	O
uses	O
IPv6	B-Protocol
to	O
reach	O
intranet	B-General_Concept
resources	O
or	O
other	O
DirectAccess	B-Application
clients	O
.	O
</s>
<s>
This	O
technology	O
encapsulates	O
the	O
IPv6	B-Protocol
traffic	O
over	O
IPv4	B-Protocol
to	O
be	O
able	O
to	O
reach	O
the	O
intranet	B-General_Concept
over	O
the	O
Internet	O
,	O
which	O
still	O
(	O
mostly	B-Architecture
)	O
relies	O
on	O
IPv4	B-Protocol
traffic	O
.	O
</s>
<s>
All	O
traffic	O
to	O
the	O
intranet	B-General_Concept
is	O
encrypted	O
using	O
IPsec	B-Protocol
and	O
encapsulated	O
in	O
IPv4	B-Protocol
packets	O
(	O
if	O
a	O
native	O
IPv6	B-Protocol
connection	O
cannot	O
be	O
established	O
)	O
,	O
which	O
means	O
that	O
in	O
most	O
cases	O
,	O
no	O
configuration	O
of	O
firewalls	O
or	O
proxies	O
should	O
be	O
required	O
.	O
</s>
<s>
A	O
DirectAccess	B-Application
client	O
can	O
use	O
one	O
of	O
several	O
tunneling	O
technologies	O
,	O
depending	O
on	O
the	O
configuration	O
of	O
the	O
network	O
the	O
client	O
is	O
connected	O
to	O
.	O
</s>
<s>
The	O
client	O
can	O
use	O
6to4	B-Protocol
,	O
Teredo	B-Protocol
tunneling	I-Protocol
,	O
or	O
IP-HTTPS	B-Protocol
,	O
provided	O
the	O
server	O
is	O
configured	O
correctly	O
to	O
be	O
able	O
to	O
use	O
them	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
client	O
that	O
is	O
connected	O
to	O
the	O
Internet	O
directly	O
will	O
use	O
6to4	B-Protocol
,	O
but	O
if	O
it	O
is	O
inside	O
a	O
NATed	O
network	O
,	O
it	O
will	O
use	O
Teredo	O
instead	O
.	O
</s>
<s>
In	O
addition	O
,	O
Windows	B-Device
Server	I-Device
2012	I-Device
provides	O
two	O
backward	O
compatibility	O
services	O
DNS64	O
and	O
NAT64	B-Protocol
,	O
which	O
allows	O
DirectAccess	B-Application
clients	O
to	O
communicate	O
with	O
servers	O
inside	O
the	O
corporate	O
network	O
even	O
if	O
those	O
servers	O
are	O
only	O
capable	O
of	O
IPv4	B-Protocol
networking	O
.	O
</s>
<s>
Due	O
to	O
the	O
globally	O
routable	O
nature	O
of	O
IPv6	B-Protocol
,	O
computers	O
on	O
the	O
corporate	O
network	O
can	O
also	O
initiate	O
a	O
connection	O
to	O
DirectAccess	B-Application
clients	O
,	O
which	O
allows	O
them	O
to	O
remotely	O
manage	O
(	O
Manage	O
Out	O
)	O
these	O
clients	O
at	O
any	O
time	O
.	O
</s>
<s>
DirectAccess	B-Application
can	O
be	O
deployed	O
for	O
multiple	O
sites	O
.	O
</s>
<s>
It	O
allows	O
for	O
a	O
secure	O
encrypted	O
VPN	B-Application
.	O
</s>
<s>
DirectAccess	B-Application
With	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
or	O
UAG	O
requires	O
:	O
</s>
<s>
One	O
or	O
more	O
DirectAccess	B-Application
servers	O
running	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
with	O
two	O
network	O
adapters	O
:	O
one	O
that	O
is	O
connected	O
directly	O
to	O
the	O
Internet	O
,	O
and	O
a	O
second	O
that	O
is	O
connected	O
to	O
the	O
intranet	B-General_Concept
.	O
</s>
<s>
On	O
the	O
DirectAccess	B-Application
server	O
,	O
at	O
least	O
two	O
consecutive	O
,	O
public	O
IPv4	B-Protocol
addresses	O
assigned	O
to	O
the	O
network	O
adapter	O
that	O
is	O
connected	O
to	O
the	O
Internet	O
.	O
</s>
<s>
At	O
least	O
one	O
domain	B-Protocol
controller	I-Protocol
and	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
server	O
running	O
Windows	O
Server	O
2008	O
SP2	O
or	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
.	O
</s>
<s>
Public	B-Architecture
key	I-Architecture
infrastructure	I-Architecture
(	O
PKI	O
)	O
to	O
issue	O
computer	O
certificates	O
.	O
</s>
<s>
DirectAccess	B-Application
With	O
Windows	B-Device
Server	I-Device
2012	I-Device
requires	O
:	O
</s>
<s>
One	O
or	O
more	O
DirectAccess	B-Application
servers	O
running	O
Windows	B-Device
Server	I-Device
2012	I-Device
with	O
one	O
or	O
more	O
network	O
adapters	O
.	O
</s>
<s>
At	O
least	O
one	O
domain	B-Protocol
controller	I-Protocol
and	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
server	O
running	O
Windows	O
Server	O
2008	O
SP2	O
or	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
.	O
</s>
<s>
A	O
Public	B-Architecture
Key	I-Architecture
Infrastructure	I-Architecture
is	O
not	O
required	O
for	O
Windows	B-Application
8	I-Application
Clients	O
.	O
</s>
