<s>
SIP	B-Protocol
trunking	I-Protocol
is	O
a	O
voice	B-Application
over	I-Application
Internet	I-Application
Protocol	I-Application
(	O
VoIP	B-Application
)	O
technology	O
and	O
streaming	O
media	O
service	O
based	O
on	O
the	O
Session	B-Application
Initiation	I-Application
Protocol	I-Application
(	O
SIP	O
)	O
by	O
which	O
Internet	B-Protocol
telephony	I-Protocol
service	I-Protocol
providers	I-Protocol
(	O
ITSPs	B-Protocol
)	O
deliver	O
telephone	O
services	O
and	O
unified	B-Protocol
communications	I-Protocol
to	O
customers	O
equipped	O
with	O
SIP-based	O
private	O
branch	O
exchange	O
(	O
IP-PBX	O
)	O
and	O
unified	B-Protocol
communications	I-Protocol
facilities	O
.	O
</s>
<s>
Most	O
unified	B-Protocol
communications	I-Protocol
applications	O
provide	O
voice	O
,	O
video	O
,	O
and	O
other	O
streaming	O
media	O
applications	O
such	O
as	O
desktop	O
sharing	O
,	O
web	O
conferencing	O
,	O
and	O
shared	O
whiteboard	O
.	O
</s>
<s>
The	O
architecture	O
of	O
SIP	B-Protocol
trunking	I-Protocol
provides	O
a	O
partitioning	O
of	O
the	O
unified	B-Protocol
communications	I-Protocol
network	O
into	O
two	O
different	O
domains	O
of	O
expertise	O
:	O
</s>
<s>
Private	O
domain	O
:	O
refers	O
to	O
a	O
part	O
of	O
the	O
network	O
connected	O
to	O
a	O
PBX	O
or	O
unified	B-Protocol
communications	I-Protocol
server	O
.	O
</s>
<s>
The	O
interconnection	O
between	O
the	O
two	O
domains	O
must	O
occur	O
through	O
a	O
SIP	B-Protocol
trunk	I-Protocol
.	O
</s>
<s>
The	O
interconnection	O
between	O
the	O
two	O
domains	O
,	O
created	O
by	O
transport	O
via	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
,	O
involves	O
setting	O
specific	O
rules	O
and	O
regulations	O
as	O
well	O
as	O
the	O
ability	O
to	O
handle	O
some	O
services	O
and	O
protocols	O
that	O
fall	O
under	O
the	O
name	O
of	O
SIP	B-Protocol
trunking	I-Protocol
.	O
</s>
<s>
The	O
ITSP	B-Protocol
is	O
responsible	O
to	O
the	O
applicable	O
regulatory	O
authority	O
regarding	O
all	O
the	O
following	O
law	O
obligations	O
of	O
the	O
public	O
domain	O
:	O
</s>
<s>
The	O
control	O
of	O
access	O
(	O
Class	O
5	O
softswitch	B-Device
)	O
;	O
</s>
<s>
Network-border	O
elements	O
that	O
separate	O
the	O
Public	O
Domain	O
from	O
the	O
Private	O
Domain	O
,	O
implementing	O
all	O
the	O
appropriate	O
ITSP	B-Protocol
phone	O
security	O
policies	O
.	O
</s>
