<s>
Origination	B-Protocol
in	O
VOIP	B-Application
telephony	I-Application
refers	O
to	O
calls	O
that	O
originate	O
in	O
the	O
PSTN	O
public	O
switched	O
telephone	O
network	O
and	O
are	O
carried	O
to	O
their	O
destination	O
over	O
the	O
Internet	O
.	O
</s>
<s>
A	O
VoIP	B-Application
call	I-Application
is	O
initiated	O
between	O
two	O
points	O
,	O
the	O
initiation	O
point	O
is	O
known	O
as	O
originator	O
and	O
the	O
destination	O
point	O
is	O
known	O
as	O
terminator	O
.	O
</s>
<s>
An	O
Internet	B-Protocol
Telephony	I-Protocol
Service	I-Protocol
Provider	I-Protocol
(	O
ITSP	B-Protocol
)	O
involved	O
in	O
the	O
origination	B-Protocol
of	O
telephone	O
calls	O
usually	O
offers	O
either	O
or	O
both	O
of	O
“	O
PC	O
to	O
Phone	O
calls	O
”	O
and	O
“	O
Phone	O
to	O
Phone	O
calls	O
”	O
.	O
</s>
<s>
The	O
two	O
major	O
business	O
models	O
for	O
VoIP	B-Application
Originator	O
are	O
“	O
Prepaid	O
”	O
and	O
“	O
Postpaid	O
”	O
.	O
</s>
<s>
Hardware	O
requirements	O
for	O
VoIP	B-Application
origination	B-Protocol
are	O
simple	O
.	O
</s>
<s>
The	O
only	O
hardware	O
needed	O
is	O
a	O
gateway	B-Application
that	O
takes	O
calls	O
off	O
the	O
Internet	O
and	O
delivers	O
them	O
onto	O
PSTN	O
lines	O
.	O
</s>
<s>
All	O
VoIP	B-Application
originators	O
require	O
a	O
call	O
termination	O
arrangement	O
with	O
a	O
terminator	O
called	O
VoIP	B-Application
terminator	O
.	O
</s>
<s>
An	O
ITSP	B-Protocol
(	O
Internet	B-Protocol
Telephony	I-Protocol
Service	I-Protocol
Provider	I-Protocol
)	O
involved	O
in	O
the	O
origination	B-Protocol
of	O
telephone	O
calls	O
usually	O
offers	O
either	O
or	O
both	O
of	O
:	O
</s>
<s>
Hardware	O
requirements	O
for	O
VoIP	B-Application
origination	B-Protocol
are	O
simple	O
.	O
</s>
<s>
The	O
only	O
hardware	O
needed	O
is	O
a	O
gateway	B-Application
that	O
takes	O
calls	O
off	O
the	O
Internet	O
and	O
delivers	O
them	O
onto	O
PSTN	O
lines	O
.	O
</s>
<s>
A	O
gateway	B-Application
therefore	O
has	O
two	O
types	O
of	O
Interfaces	O
.	O
</s>
<s>
An	O
Ethernet	O
interface	O
that	O
connects	O
the	O
gateway	B-Application
to	O
the	O
Internet	O
.	O
</s>
<s>
One	O
or	O
more	O
telephony	O
interfaces	O
taking	O
analog	O
or	O
digital	B-Application
phone	I-Application
lines	O
.	O
</s>
<s>
An	O
analog	O
line	O
can	O
take	O
one	O
phone	O
call	O
at	O
a	O
time	O
while	O
a	O
digital	B-General_Concept
line	O
can	O
take	O
more	O
.	O
</s>
<s>
A	O
T1	B-Protocol
line	I-Protocol
takes	O
24	O
calls	O
and	O
supports	O
1.5	O
Mbits	O
while	O
an	O
E1	O
line	O
takes	O
30	O
calls	O
and	O
supports	O
2Mbits	O
simultaneously	O
.	O
</s>
<s>
A	O
gatekeeper	B-General_Concept
is	O
an	O
application	B-Application
that	O
receives	O
the	O
registration	O
requests	O
and	O
calls	O
from	O
a	O
dialer	O
.	O
</s>
<s>
When	O
a	O
user	O
signs	O
into	O
the	O
dialer	O
,	O
the	O
request	O
goes	O
to	O
the	O
gatekeeper	B-General_Concept
.	O
</s>
<s>
The	O
gatekeeper	B-General_Concept
asks	O
the	O
Radius	B-Protocol
server	I-Protocol
to	O
see	O
if	O
the	O
username	O
and	O
password	O
are	O
correct	O
and	O
valid	O
.	O
</s>
<s>
The	O
Radius	B-Protocol
server	I-Protocol
queries	O
the	O
database	O
and	O
sends	O
a	O
yes/no	O
reply	O
to	O
the	O
gatekeeper	B-General_Concept
.	O
</s>
<s>
When	O
the	O
user	O
dials	O
a	O
phone	O
number	O
in	O
the	O
dialer	O
,	O
the	O
request	O
again	O
goes	O
to	O
the	O
gatekeeper	B-General_Concept
,	O
gatekeeper	B-General_Concept
again	O
asks	O
the	O
Radius	B-Protocol
server	I-Protocol
if	O
the	O
user	O
is	O
allowed	O
to	O
make	O
this	O
call	O
and	O
has	O
enough	O
money	O
to	O
initiate	O
it	O
.	O
</s>
<s>
The	O
Radius	B-Protocol
server	I-Protocol
asks	O
the	O
billing	O
server	B-Application
for	O
the	O
maximum	O
duration	O
of	O
call	O
can	O
be	O
allowed	O
to	O
this	O
user	O
based	O
on	O
the	O
amount	O
of	O
money	O
remaining	O
in	O
his	O
account	O
or	O
prepaid	O
card	O
.	O
</s>
<s>
The	O
billing	O
solution	O
looks	O
up	O
the	O
destination	O
of	O
the	O
call	O
,	O
finds	O
the	O
appropriate	O
rate	O
based	O
on	O
the	O
peak/	O
off	O
peak	O
hours	O
and	O
the	O
type	O
of	O
the	O
customer	O
and	O
informs	O
the	O
Radius	B-Protocol
server	I-Protocol
exact	O
duration	O
in	O
seconds	O
that	O
the	O
user	O
can	O
call	O
to	O
this	O
destination	O
.	O
</s>
<s>
The	O
same	O
info	O
is	O
returned	O
by	O
the	O
Radius	B-Protocol
server	I-Protocol
to	O
the	O
gatekeeper	B-General_Concept
and	O
the	O
gatekeeper	B-General_Concept
informs	O
the	O
dialer	O
the	O
IP	B-Protocol
address	I-Protocol
of	O
the	O
destination	O
gateway	B-Application
that	O
can	O
deliver	O
the	O
voice	O
call	O
to	O
the	O
destination	O
.	O
</s>
<s>
If	O
they	O
continue	O
to	O
talk	O
until	O
the	O
maximum	O
allowed	O
duration	O
of	O
the	O
call	O
,	O
the	O
call	O
is	O
disconnected	O
by	O
the	O
gatekeeper	B-General_Concept
,	O
so	O
the	O
user	O
does	O
n't	O
consume	O
any	O
amount	O
above	O
the	O
available	O
limit	O
.	O
</s>
<s>
Whenever	O
a	O
call	O
is	O
disconnected	O
naturally	O
or	O
forcefully	O
by	O
the	O
gatekeeper	B-General_Concept
,	O
the	O
gatekeeper	B-General_Concept
informs	O
the	O
billing	O
application	B-Application
with	O
the	O
details	O
of	O
that	O
call	O
.	O
</s>
<s>
The	O
billing	O
application	B-Application
computes	O
the	O
total	O
call	O
charges	O
and	O
deducts	O
the	O
amount	O
from	O
the	O
calling	O
customer	O
's	O
account	O
or	O
prepaid	O
card	O
.	O
</s>
<s>
All	O
VoIP	B-Application
originators	O
require	O
a	O
call	O
termination	O
arrangement	O
with	O
a	O
terminator	O
called	O
VoIP	B-Application
terminator	O
.	O
</s>
<s>
A	O
PC	O
to	O
Phone	O
provider	O
first	O
arranges	O
a	O
softphone	B-Protocol
also	O
called	O
a	O
dialer	O
.	O
</s>
<s>
The	O
ITSP	B-Protocol
needs	O
to	O
arrange	O
a	O
set	O
of	O
servers	O
that	O
will	O
run	O
the	O
basic	O
setup	O
to	O
allow	O
them	O
to	O
receive	O
dialer	O
calls	O
and	O
send	O
them	O
to	O
different	O
terminators	O
for	O
delivery	O
.	O
</s>
<s>
A	O
database	O
application	B-Application
.	O
</s>
<s>
Phone-to-Phone	O
business	O
is	O
similar	O
in	O
nature	O
to	O
PC	O
to	O
Phone	O
business	O
,	O
except	O
for	O
the	O
fact	O
that	O
the	O
ITSP	B-Protocol
now	O
also	O
needs	O
to	O
arrange	O
for	O
originating	O
gateways	B-Application
.	O
</s>
<s>
A	O
gateway	B-Application
is	O
a	O
device	O
that	O
can	O
receive	O
a	O
phone	O
call	O
over	O
PSTN	O
and	O
convert	O
it	O
into	O
IP	O
for	O
delivery	O
over	O
Internet	O
.	O
</s>
<s>
A	O
gateway	B-Application
usually	O
has	O
a	O
fixed	O
number	O
of	O
ports	O
.	O
</s>
<s>
Analog	O
gateways	B-Application
take	O
analog	O
phone	O
lines	O
while	O
digital	B-General_Concept
gateways	B-Application
take	O
digital	B-Application
phone	I-Application
lines	O
.	O
</s>
<s>
See	O
the	O
“	O
Basics	O
of	O
VoIP	B-Application
”	O
white	O
paper	O
for	O
details	O
of	O
analog	O
and	O
digital	B-General_Concept
lines	O
.	O
</s>
<s>
Once	O
the	O
gateway	B-Application
has	O
converted	O
the	O
PSTN	O
call	O
to	O
IP	O
,	O
the	O
rest	O
of	O
the	O
delivery	O
is	O
the	O
same	O
as	O
it	O
is	O
in	O
the	O
PC	O
to	O
Phone	O
case	O
.	O
</s>
<s>
In	O
the	O
phone-to-phone	O
scenario	O
,	O
an	O
IVR	O
(	O
interactive	O
voice	O
response	O
)	O
system	O
is	O
required	O
with	O
the	O
gateway	B-Application
to	O
prompt	O
the	O
customer	O
for	O
their	O
PIN	O
.	O
</s>
<s>
The	O
PIN	O
entered	O
by	O
the	O
customer	O
is	O
taken	O
by	O
the	O
gateway	B-Application
or	O
gatekeeper	B-General_Concept
and	O
given	O
to	O
the	O
Radius	B-Protocol
server	I-Protocol
for	O
authorization	O
.	O
</s>
<s>
VoIP	B-Application
origination	B-Protocol
is	O
mostly	O
prepaid	O
nowadays	O
.	O
</s>
<s>
In	O
postpaid	O
,	O
the	O
ITSP	B-Protocol
sends	O
an	O
invoice	O
at	O
the	O
end	O
of	O
the	O
accounting	O
period	O
,	O
usually	O
a	O
month	O
,	O
and	O
the	O
customer	O
pays	O
later	O
.	O
</s>
