<s>
ZeroTier	B-Application
Inc	O
.	O
is	O
a	O
software	O
company	O
with	O
a	O
freemium	O
business	O
model	O
based	O
in	O
Irvine	O
,	O
California	O
.	O
</s>
<s>
ZeroTier	B-Application
provides	O
proprietary	B-Application
software	I-Application
,	O
SDKs	B-Application
and	O
commercial	O
products	O
and	O
services	O
to	O
create	O
and	O
manage	O
virtual	O
software-defined	O
networks	O
.	O
</s>
<s>
The	O
company	O
's	O
flagship	O
end-user	O
product	O
ZeroTier	B-Application
One	O
is	O
a	O
client	O
application	O
that	O
enables	O
devices	O
such	O
as	O
PCs	O
,	O
phones	O
,	O
servers	O
and	O
embedded	O
devices	O
to	O
securely	O
connect	O
to	O
peer-to-peer	O
virtual	O
networks	O
.	O
</s>
<s>
ZeroTier	B-Application
markets	O
proprietary	B-Application
tools	O
,	O
which	O
are	O
licensed	O
under	O
a	O
Business	O
Source	O
License	O
1.1	O
,	O
intended	O
to	O
support	O
the	O
development	O
and	O
deployment	O
of	O
virtual	O
data	B-Operating_System
centers	I-Operating_System
:	O
</s>
<s>
ZeroTier	B-Application
One	O
,	O
first	O
released	O
in	O
2014	O
,	O
is	O
a	O
portable	O
client	O
application	O
that	O
provides	O
connectivity	O
to	O
public	O
or	O
private	O
virtual	O
networks	O
.	O
</s>
<s>
Central	O
,	O
a	O
web-based	O
UI	B-Application
portal	O
for	O
managing	O
virtual	O
networks	O
.	O
</s>
<s>
libzt	O
(	O
SDK	O
)	O
,	O
a	O
linkable	O
library	O
that	O
provides	O
the	O
functionality	O
of	O
ZeroTier	B-Application
One	O
but	O
that	O
can	O
be	O
embedded	O
in	O
applications	O
or	O
services	O
.	O
</s>
<s>
The	O
ZeroTier	B-Application
client	O
is	O
used	O
to	O
connect	O
to	O
virtual	O
networks	O
previously	O
created	O
in	O
the	O
ZeroTier	B-Application
Central	O
web-based	O
UI	B-Application
.	O
</s>
<s>
STUN	B-Protocol
and	O
hole	O
punching	O
are	O
used	O
to	O
establish	O
direct	O
connections	O
between	O
peers	O
behind	O
NAT	B-Protocol
.	O
</s>
<s>
Direct	O
connection	O
route	O
discovery	O
is	O
made	O
with	O
the	O
help	O
of	O
a	O
global	O
network	O
of	O
root	O
servers	O
via	O
a	O
mechanism	O
similar	O
to	O
ICE	O
in	O
WebRTC	B-Protocol
.	O
</s>
<s>
Virtual	O
networks	O
are	O
created	O
and	O
managed	O
using	O
a	O
ZeroTier	B-Application
controller	O
.	O
</s>
<s>
Management	O
is	O
done	O
using	O
an	O
API	B-General_Concept
,	O
proprietary	B-Application
web-based	O
UI	B-Application
(	O
)	O
,	O
open-source	O
web-based	O
or	O
CLI	B-Application
alternative	O
.	O
</s>
<s>
Using	O
root	O
servers	O
other	O
than	O
those	O
hosted	O
by	O
ZeroTier	B-Application
Inc	O
.	O
is	O
impeded	O
by	O
the	O
software	O
's	O
license	O
.	O
</s>
<s>
The	O
following	O
considerations	O
apply	O
to	O
ZeroTier	B-Application
's	O
use	O
as	O
an	O
SDWAN	B-Architecture
or	O
VPN	B-Application
application	O
:	O
</s>
<s>
All	O
traffic	O
is	O
encrypted	O
end	O
to	O
end	O
on	O
OSI	O
layer	O
1	O
using	O
256-bit	O
Salsa20	B-Algorithm
and	O
authenticated	O
using	O
the	O
Poly1305	B-Algorithm
message	O
authentication	O
(	O
MAC	B-Device
)	O
algorithm	O
.	O
</s>
<s>
MAC	B-Device
is	O
computed	O
after	O
encryption	O
(	O
encrypt-then-MAC	O
)	O
and	O
the	O
cipher/MAC	O
composition	O
used	O
is	O
identical	O
to	O
the	O
NaCl	O
reference	O
implementation	O
.	O
</s>
<s>
ZeroTier	B-Application
One	O
is	O
available	O
on	O
multiple	O
platforms	O
and	O
in	O
multiple	O
forms	O
:	O
</s>
