<s>
The	O
TV	B-Protocol
Network	I-Protocol
Protocol	I-Protocol
or	O
TVNP	B-Protocol
as	O
it	O
is	O
more	O
commonly	O
referred	O
to	O
is	O
an	O
open	O
network	O
protocol	O
developed	O
to	O
enable	O
CCTV	O
systems	O
from	O
any	O
manufacturer	O
to	O
be	O
integrated	O
into	O
an	O
existing	O
CCTV	O
network	O
.	O
</s>
<s>
As	O
of	O
late	O
of	O
2011	O
there	O
are	O
at	O
least	O
eight	O
manufacturers	O
who	O
have	O
a	O
partial	O
or	O
full	O
TVNP	B-Protocol
interface	O
,	O
including	O
:	O
</s>
<s>
TVNP	B-Protocol
layers	O
are	O
broadly	O
based	O
on	O
the	O
OSI	O
model	O
.	O
</s>
<s>
TVNP	B-Protocol
Layer	O
2	O
and	O
3	O
correspond	O
to	O
OSI	O
Layers	O
2	O
and	O
3	O
.	O
</s>
<s>
When	O
used	O
over	O
RS-232	O
only	O
,	O
TVNP	B-Protocol
Layer	O
1	O
corresponds	O
to	O
OSI	O
Layer	O
1	O
.	O
</s>
<s>
TVNP	B-Protocol
Layer	O
4	O
is	O
equivalent	O
to	O
OSI	O
Layer	O
7	O
.	O
</s>
<s>
Structuring	O
the	O
TVNP	B-Protocol
in	O
such	O
a	O
way	O
means	O
that	O
as	O
future	O
needs	O
and	O
provisions	O
change	O
,	O
aspects	O
of	O
one	O
layer	O
can	O
be	O
enhanced	O
or	O
modified	O
without	O
the	O
need	O
for	O
change	O
to	O
the	O
other	O
layers	O
.	O
</s>
<s>
A	O
digital	O
replacement	O
of	O
TVNP	B-Protocol
has	O
been	O
produced	O
by	O
Costain	O
,	O
Highways	O
England	O
,	O
Transport	O
for	O
London	O
and	O
the	O
Metropolitan	O
Police	O
called	O
DVNP	O
or	O
Digital	O
Video	O
Network	O
Protocol	O
.	O
</s>
<s>
DVNP	O
uses	O
IP	O
networks	O
to	O
link	O
CCTV	O
systems	O
from	O
different	O
manufacturers	O
with	O
control	O
message	O
sent	O
using	O
HTTP	B-Protocol
GET	O
messages	O
and	O
video	O
streamed	O
using	O
standard	O
video	O
streaming	O
protocols	O
like	O
RTMP	O
and	O
RTSP	O
.	O
</s>
