<s>
The	O
Network	B-Protocol
Voice	I-Protocol
Protocol	I-Protocol
(	O
NVP	B-Protocol
)	O
was	O
a	O
pioneering	O
computer	O
network	O
protocol	O
for	O
transporting	O
human	O
speech	O
over	O
packetized	O
communications	O
networks	O
.	O
</s>
<s>
It	O
was	O
an	O
early	O
example	O
of	O
Voice	B-Application
over	I-Application
Internet	I-Application
Protocol	I-Application
technology	O
.	O
</s>
<s>
NVP	B-Protocol
was	O
first	O
defined	O
and	O
implemented	O
in	O
1974	O
,	O
with	O
definition	O
led	O
by	O
the	O
“	O
Speech	O
”	O
project	O
at	O
ISI	O
,	O
the	O
USC	O
Information	O
Sciences	O
Institute	O
following	O
initial	O
work	O
begun	O
in	O
1973	O
.	O
</s>
<s>
The	O
project	O
's	O
stated	O
goals	O
were	O
"	O
to	O
develop	O
and	O
demonstrate	O
the	O
feasibility	O
of	O
secure	O
,	O
high-quality	O
,	O
low-bandwidth	O
,	O
real-time	O
,	O
full-duplex	O
(	O
two-way	O
)	O
digital	O
voice	O
communications	O
over	O
packet-switched	O
computer	O
communications	O
networks	O
...	O
[	O
and	O
to ]	O
supply	O
digitized	O
speech	O
which	O
can	O
be	O
secured	O
by	O
existing	O
encryption	O
devices	O
.	O
</s>
<s>
NVP	B-Protocol
’s	O
first	O
demonstration	O
was	O
in	O
August	O
1974	O
between	O
the	O
groups	O
at	O
ISI	O
and	O
MIT	O
Lincoln	O
Laboratory	O
.	O
</s>
<s>
Necessary	O
subnet	O
(	O
IMP-to-IMP	O
)	O
changes	O
for	O
real-time	O
packet	B-Protocol
forwarding	O
were	O
discussed	O
at	O
ISI	O
in	O
March	O
1974	O
,	O
chaired	O
by	O
Bob	O
Kahn	O
,	O
DARPA	O
’s	O
program	O
director	O
for	O
the	O
speech	O
project	O
.	O
</s>
<s>
NVP	B-Protocol
was	O
used	O
to	O
send	O
speech	O
between	O
distributed	O
sites	O
on	O
the	O
ARPANET	O
using	O
several	O
different	O
voice-encoding	O
techniques	O
,	O
including	O
linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
(	O
LPC	O
)	O
and	O
continuously	B-Algorithm
variable	I-Algorithm
slope	I-Algorithm
delta	I-Algorithm
modulation	I-Algorithm
(	O
CVSD	B-Algorithm
)	O
.	O
</s>
<s>
NVP	B-Protocol
was	O
used	O
by	O
experimental	O
Voice	B-Protocol
Funnel	I-Protocol
equipment	O
(	O
circa	O
February	O
1981	O
)	O
,	O
based	O
on	O
BBN	B-Device
Butterfly	I-Device
computers	I-Device
,	O
as	O
part	O
of	O
ongoing	O
ARPA	O
research	O
into	O
packetized	O
audio	O
.	O
</s>
<s>
ARPA	O
staff	O
and	O
contractors	O
used	O
the	O
Voice	B-Protocol
Funnel	I-Protocol
,	O
and	O
related	O
video	O
facilities	O
,	O
to	O
do	O
three-way	O
and	O
four-way	O
video	O
conferencing	O
among	O
a	O
handful	O
of	O
US	O
East	O
and	O
West	O
Coast	O
sites	O
.	O
</s>
<s>
For	O
each	O
encoding	O
scheme	O
(	O
vocoder	O
)	O
a	O
frame	O
was	O
defined	O
as	O
a	O
packet	B-Protocol
containing	O
the	O
negotiated	O
transmission	O
interval	O
of	O
a	O
number	O
of	O
digitized	O
voice	O
samples	O
.	O
</s>
<s>
NVP	B-Protocol
was	O
transported	O
over	O
the	O
Internet	B-Protocol
Stream	I-Protocol
Protocol	I-Protocol
(	O
ST	O
)	O
and	O
a	O
later	O
version	O
called	O
Stream	O
Protocol	O
,	O
version	O
2	O
(	O
ST-II	O
)	O
,	O
both	O
connection-oriented	O
versions	O
of	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
and	O
which	O
carried	O
the	O
IP	B-Protocol
protocol	I-Protocol
version	O
5	O
.	O
</s>
