<s>
GNU	B-Application
SIP	I-Application
Witch	I-Application
is	O
a	O
free	O
SIP	O
server	O
software	O
with	O
Peer-to-peer	O
capabilities	O
from	O
the	B-Application
GNU	I-Application
Project	I-Application
.	O
</s>
<s>
It	O
is	O
the	O
GNU	O
implementation	O
of	O
the	O
Session	B-Application
Initiation	I-Application
Protocol	I-Application
(	O
SIP	O
)	O
,	O
which	O
is	O
being	O
used	O
for	O
the	O
routing	O
of	O
the	O
calls	O
.	O
</s>
<s>
SIP	O
Witch	O
is	O
released	O
as	O
free	B-Application
software	I-Application
under	O
the	O
terms	O
of	O
version	O
3	O
or	O
later	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
.	O
</s>
<s>
It	O
is	O
designed	O
for	O
Linux	B-Application
,	O
macOS	B-Application
,	O
BSD	B-Operating_System
and	O
Windows	B-Application
and	O
planned	O
support	O
for	O
Android	B-Application
.	O
</s>
<s>
In	O
the	O
popular	O
Linux	B-Application
distributions	O
Ubuntu	B-Operating_System
and	O
Fedora	O
it	O
may	O
be	O
installed	O
directly	O
from	O
the	O
standard	O
package	O
sources	O
.	O
</s>
<s>
SIP	O
Witch	O
is	O
written	O
in	O
the	O
programming	O
language	O
C++	B-Language
and	O
uses	O
the	O
uCommon	O
,	O
eXosip	O
and	O
GNU	B-Protocol
oSIP	I-Protocol
libraries	B-Library
.	O
</s>
<s>
The	O
software	O
enables	O
Voice	B-Application
over	I-Application
IP	I-Application
as	O
part	O
of	O
a	O
self-organising	O
Peer-to-peer	O
telephone	O
network	O
.	O
</s>
<s>
It	O
supports	O
features	O
like	O
call	O
forwarding	O
,	O
call	O
distribution	O
,	O
call	O
hold	O
,	O
presence	B-Protocol
information	I-Protocol
and	O
(	O
text	O
)	O
messages	O
,	O
supports	O
encrypted	B-Protocol
calls	O
and	O
also	O
enables	O
NAT	B-Protocol
traversal	I-Protocol
to	O
establish	O
the	O
peer-to-peer	O
connections	O
.	O
</s>
<s>
It	O
is	O
being	O
used	O
as	O
a	O
component	O
of	O
GNU	O
Free	O
Call	O
,	O
which	O
is	O
supposed	O
to	O
be	O
an	O
alternative	O
to	O
Skype	B-Application
.	O
</s>
