<s>
Distributed	B-Protocol
Network	I-Protocol
Protocol	I-Protocol
3	O
(	O
DNP3	B-Protocol
)	O
is	O
a	O
set	O
of	O
communications	O
protocols	O
used	O
between	O
components	O
in	O
process	O
automation	O
systems	O
.	O
</s>
<s>
It	O
was	O
developed	O
for	O
communications	O
between	O
various	O
types	O
of	O
data	B-Algorithm
acquisition	I-Algorithm
and	O
control	O
equipment	O
.	O
</s>
<s>
Control	O
Centers	O
)	O
,	O
Remote	B-Device
Terminal	I-Device
Units	I-Device
(	O
RTUs	O
)	O
,	O
and	O
Intelligent	O
Electronic	O
Devices	O
(	O
IEDs	O
)	O
.	O
</s>
<s>
Competing	O
standards	O
include	O
the	O
older	O
Modbus	B-Protocol
protocol	O
and	O
the	O
newer	O
IEC	O
61850	O
protocol	O
.	O
</s>
<s>
While	O
IEC	B-Protocol
60870-5	I-Protocol
was	O
still	O
under	O
development	O
and	O
had	O
not	O
been	O
standardized	O
,	O
there	O
was	O
a	O
need	O
to	O
create	O
a	O
standard	O
that	O
would	O
allow	O
interoperability	O
between	O
various	O
vendors	O
 '	O
SCADA	O
components	O
for	O
the	O
electrical	O
grid	O
.	O
</s>
<s>
Thus	O
,	O
in	O
1993	O
,	O
GE-Harris	O
Canada	O
(	O
formerly	O
known	O
as	O
Westronic	O
)	O
used	O
the	O
partially	O
completed	O
IEC	B-Protocol
60870-5	I-Protocol
protocol	O
specifications	O
as	O
the	O
basis	O
for	O
an	O
open	O
and	O
immediately	O
implementable	O
protocol	O
that	O
specifically	O
catered	O
to	O
North	O
American	O
requirements	O
.	O
</s>
<s>
Because	O
smart	B-Architecture
grid	I-Architecture
applications	O
generally	O
assume	O
access	O
by	O
third	O
parties	O
to	O
the	O
same	O
physical	O
networks	O
and	O
underlying	O
IP	O
infrastructure	O
of	O
the	O
grid	O
,	O
much	O
work	O
has	O
been	O
done	O
to	O
add	O
Secure	O
Authentication	O
features	O
to	O
the	O
DNP3	B-Protocol
protocol	O
.	O
</s>
<s>
The	O
DNP3	B-Protocol
protocol	O
is	O
compliant	O
with	O
IEC	O
62351-5	O
.	O
</s>
<s>
The	O
DNP3	B-Protocol
protocol	O
is	O
also	O
referenced	O
in	O
IEEE	O
Std	O
.	O
</s>
<s>
It	O
is	O
recommended	O
to	O
use	O
DNP3	B-Protocol
with	O
TLS	O
,	O
Transport	B-Architecture
Layer	I-Architecture
Security	O
,	O
in	O
accordance	O
with	O
IEC	O
62351-3	O
.	O
</s>
<s>
The	O
DNP3	B-Protocol
protocol	O
has	O
significant	O
features	O
that	O
make	O
it	O
more	O
robust	O
,	O
efficient	O
,	O
and	O
interoperable	O
than	O
older	O
protocols	O
such	O
as	O
Modbus	B-Protocol
,	O
at	O
the	O
cost	O
of	O
higher	O
complexity	O
.	O
</s>
<s>
In	O
terms	O
of	O
the	O
OSI	O
model	O
for	O
networks	O
,	O
DNP3	B-Protocol
specifies	O
a	O
layer	B-Protocol
2	I-Protocol
protocol	O
.	O
</s>
<s>
It	O
provides	O
multiplexing	O
,	O
data	O
fragmentation	O
,	O
error	O
checking	O
,	O
link	O
control	O
,	O
prioritization	O
,	O
and	O
layer	B-Protocol
2	I-Protocol
addressing	O
services	O
for	O
user	O
data	O
.	O
</s>
<s>
It	O
also	O
defines	O
a	O
Transport	O
function	O
(	O
somewhat	O
similar	O
to	O
the	O
function	O
of	O
layer	B-Architecture
4	I-Architecture
)	O
and	O
an	O
Application	O
Layer	O
(	O
layer	O
7	O
)	O
that	O
defines	O
functions	O
and	O
generic	O
data	O
types	O
suitable	O
for	O
common	O
SCADA	O
applications	O
.	O
</s>
<s>
The	O
DNP3	B-Protocol
frame	B-Protocol
strongly	O
resembles	O
,	O
but	O
is	O
not	O
identical	O
to	O
the	O
IEC	B-Protocol
60870-5	I-Protocol
FT3	O
frame	B-Protocol
.	O
</s>
<s>
The	O
improved	O
bandwidth	O
efficiency	O
is	O
accomplished	O
through	O
event	O
oriented	O
data	B-General_Concept
reporting	I-General_Concept
.	O
</s>
<s>
The	O
Remote	B-Device
Terminal	I-Device
Unit	I-Device
monitors	O
data	O
points	O
and	O
generates	O
events	O
when	O
it	O
determines	O
that	O
the	O
data	O
should	O
be	O
reported	O
(	O
for	O
example	O
,	O
when	O
it	O
changes	O
value	O
)	O
.	O
</s>
<s>
The	O
Remote	B-Device
Terminal	I-Device
Unit	I-Device
is	O
initially	O
interrogated	O
with	O
what	O
DNP3	B-Protocol
terms	O
an	O
"	O
Integrity	O
Poll	O
"	O
(	O
a	O
combined	O
Read	O
of	O
Class	O
1	O
,	O
2	O
,	O
3	O
and	O
0	O
data	O
)	O
.	O
</s>
<s>
This	O
causes	O
the	O
Remote	B-Device
Terminal	I-Device
Unit	I-Device
to	O
send	O
all	O
buffered	O
events	O
and	O
also	O
all	O
static	O
point	O
data	O
to	O
the	O
Master	O
station	O
.	O
</s>
<s>
The	O
Remote	B-Device
Terminal	I-Device
Unit	I-Device
can	O
also	O
be	O
configured	O
to	O
spontaneously	O
report	O
Class	O
1	O
,	O
2	O
,	O
or	O
3	O
data	O
,	O
when	O
it	O
becomes	O
available	O
.	O
</s>
<s>
The	O
DNP3	B-Protocol
protocol	O
supports	O
time	O
synchronization	O
with	O
an	O
RTU	O
.	O
</s>
<s>
The	O
DNP3	B-Protocol
protocol	O
has	O
a	O
substantial	O
library	O
of	O
common	O
point-oriented	O
objects	O
.	O
</s>
<s>
The	O
focus	O
of	O
this	O
extensive	O
library	O
was	O
to	O
eliminate	O
the	O
need	O
for	O
bit-mapping	O
data	O
over	O
other	O
objects	O
,	O
as	O
is	O
often	O
done	O
in	O
many	O
Modbus	B-Protocol
installations	O
.	O
</s>
<s>
A	O
Remote	B-Device
Terminal	I-Device
Unit	I-Device
for	O
the	O
DNP3	B-Protocol
protocol	O
can	O
be	O
a	O
small	O
,	O
simple	O
embedded	O
device	O
,	O
or	O
it	O
can	O
be	O
a	O
large	O
,	O
complex	O
rack	O
filled	O
with	O
equipment	O
.	O
</s>
<s>
The	O
IEEE	O
adopted	O
DNP3	B-Protocol
as	O
on	O
July	O
23	O
,	O
2010	O
.	O
</s>
<s>
The	O
new	O
version	O
is	O
capable	O
of	O
using	O
Public	B-Architecture
Key	I-Architecture
Infrastructure	I-Architecture
,	O
and	O
it	O
facilitates	O
remote	O
key	O
changes	O
.	O
</s>
