<s>
University	O
of	O
Tsukuba	O
Virtual	B-Application
Private	I-Application
Network	I-Application
,	O
UT-VPN	B-Protocol
is	O
a	O
free	B-Application
and	I-Application
open	I-Application
source	I-Application
software	I-Application
application	O
that	O
implements	O
virtual	B-Application
private	I-Application
network	I-Application
(	O
VPN	B-Application
)	O
techniques	O
for	O
creating	O
secure	O
point-to-point	O
or	O
site-to-site	O
connections	O
in	O
routed	O
or	O
bridged	O
configurations	O
and	O
remote	O
access	O
facilities	O
.	O
</s>
<s>
It	O
uses	O
SSL/TLS	B-Protocol
security	O
for	O
encryption	O
and	O
is	O
capable	O
of	O
traversing	O
network	B-Protocol
address	I-Protocol
translators	I-Protocol
(	O
NATs	O
)	O
and	O
firewalls	B-Application
.	O
</s>
<s>
It	O
was	O
written	O
by	O
Daiyuu	O
Nobori	O
and	O
SoftEther	B-Operating_System
Corporation	I-Operating_System
,	O
and	O
is	O
published	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
by	O
University	O
of	O
Tsukuba	O
.	O
</s>
<s>
UT-VPN	B-Protocol
has	O
compatible	O
as	O
PacketiX	B-Operating_System
VPN	I-Operating_System
product	O
of	O
SoftEther	B-Operating_System
Corporation	I-Operating_System
.	O
</s>
<s>
UT-VPN	B-Protocol
developed	O
based	O
on	O
PacketiX	B-Operating_System
VPN	I-Operating_System
,	O
but	O
some	O
functions	O
was	O
deleted	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
RADIUS	O
client	O
is	O
supported	O
by	O
PacketiX	B-Operating_System
VPN	I-Operating_System
Server	O
,	O
but	O
it	O
is	O
not	O
supported	O
by	O
UT-VPN	B-Protocol
Server	O
.	O
</s>
<s>
UT-VPN	B-Protocol
uses	O
the	O
OpenSSL	B-Language
library	O
to	O
provide	O
encryption	O
to	O
packets	O
.	O
</s>
<s>
UT-VPN	B-Protocol
offers	O
username/password	O
-based	O
authentication	O
.	O
</s>
<s>
UT-VPN	B-Protocol
is	O
software	O
to	O
consist	O
of	O
UT-VPN	B-Protocol
Server	O
and	O
UT-VPN	B-Protocol
Client	O
.	O
</s>
<s>
UT-VPN	B-Protocol
functions	O
as	O
L2-VPN	O
(	O
over	O
SSL/TLS	B-Protocol
)	O
.	O
</s>
<s>
'	O
Virtual	O
NIC	O
 '	O
(	O
virtual	O
network	O
interface	O
card	O
)	O
is	O
installed	O
in	O
OS	O
how	O
UT-VPN	B-Protocol
Client	O
was	O
installed	O
in	O
.	O
</s>
<s>
UT-VPN	B-Protocol
does	O
encapsulation	O
to	O
TCP	O
(	O
or	O
SSL/TLS	B-Protocol
)	O
packets	O
from	O
L2	O
frames	O
by	O
Virtual	O
NIC	O
.	O
</s>
<s>
UT-VPN	B-Protocol
Client	O
connects	O
with	O
UT-VPN	B-Protocol
Server	O
.	O
</s>
<s>
If	O
authorization	O
with	O
UT-VPN	B-Protocol
Server	O
succeeded	O
,	O
UT-VPN	B-Protocol
Client	O
establishes	O
connection	O
with	O
Virtual	O
HUB	O
.	O
</s>
<s>
UT-VPN	B-Protocol
Server	O
have	O
some	O
'	O
Virtual	O
HUB	O
 '	O
,	O
and	O
they	O
function	O
as	O
virtual	O
L2	O
switch	O
.	O
</s>
<s>
Virtual	O
HUB	O
does	O
handle	O
frames	O
which	O
received	O
from	O
UT-VPN	B-Protocol
Client	O
.	O
</s>
<s>
If	O
necessary	O
,	O
UT-VPN	B-Protocol
Server	O
forwards	O
encapsulated	O
L2	O
frames	O
to	O
UT-VPN	B-Protocol
Client	O
.	O
</s>
<s>
Virtual	O
HUB	O
on	O
UT-VPN	B-Protocol
Server	O
has	O
function	O
cascading	O
connection	O
for	O
Virtual	O
HUB	O
on	O
other	O
UT-VPN	B-Protocol
Server	O
.	O
</s>
<s>
UT-VPN	B-Protocol
Server	O
has	O
bridging	O
function	O
between	O
arbitrary	O
NIC	O
which	O
OS	O
has	O
and	O
virtual	O
HUB	O
.	O
</s>
<s>
UT-VPN	B-Protocol
Server	O
has	O
Virtual	O
L3	O
switch	O
function	O
.	O
</s>
<s>
Virtual	O
L3	O
switch	O
does	O
L3-switching	O
between	O
virtual	O
HUB	O
on	O
the	O
UT-VPN	B-Protocol
Server	O
.	O
</s>
<s>
*	O
If	O
it	O
is	O
the	O
environment	O
where	O
compiling	O
it	O
is	O
possible	O
of	O
the	O
source	O
code	O
,	O
UT-VPN	B-Protocol
Server	O
works	O
.	O
</s>
<s>
*	O
The	O
Virtual	O
NIC	O
does	O
not	O
work	O
in	O
other	O
UNIX	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
