<s>
DECnet	B-Protocol
is	O
a	O
suite	O
of	O
network	O
protocols	B-Protocol
created	O
by	O
Digital	O
Equipment	O
Corporation	O
.	O
</s>
<s>
Originally	O
released	O
in	O
1975	O
in	O
order	O
to	O
connect	O
two	O
PDP-11	B-Device
minicomputers	B-Architecture
,	O
it	O
evolved	O
into	O
one	O
of	O
the	O
first	O
peer-to-peer	O
network	O
architectures	O
,	O
thus	O
transforming	O
DEC	O
into	O
a	O
networking	O
powerhouse	O
in	O
the	O
1980s	O
.	O
</s>
<s>
Initially	O
built	O
with	O
three	O
layers	B-Application
,	O
it	O
later	O
(	O
1982	O
)	O
evolved	O
into	O
a	O
seven-layer	O
OSI-compliant	O
networking	O
protocol	O
.	O
</s>
<s>
DECnet	B-Protocol
was	O
built	O
right	O
into	O
the	O
DEC	O
flagship	O
operating	B-General_Concept
system	I-General_Concept
OpenVMS	B-Operating_System
since	O
its	O
inception	O
.	O
</s>
<s>
Later	O
Digital	O
ported	O
it	O
to	O
Ultrix	B-Operating_System
,	O
as	O
well	O
as	O
Apple	B-Device
Macintosh	I-Device
and	O
IBM	B-Device
PC	I-Device
running	O
variants	O
of	O
DOS	B-Device
and	O
Microsoft	B-Application
Windows	I-Application
under	O
the	O
name	O
DEC	O
Pathworks	O
,	O
allowing	O
these	O
systems	O
to	O
connect	O
to	O
DECnet	B-Protocol
networks	O
of	O
VAX	B-Device
machines	O
as	O
terminal	O
nodes	O
.	O
</s>
<s>
While	O
the	O
DECnet	B-Protocol
protocols	B-Protocol
were	O
designed	O
entirely	O
by	O
Digital	O
Equipment	O
Corporation	O
,	O
DECnet	B-Protocol
Phase	O
II	O
(	O
and	O
later	O
)	O
were	O
open	O
standards	O
with	O
published	O
specifications	O
,	O
and	O
several	O
implementations	O
were	O
developed	O
outside	O
DEC	O
,	O
including	O
ones	O
for	O
FreeBSD	B-Operating_System
and	O
Linux	B-Application
.	O
</s>
<s>
DECnet	B-Protocol
code	O
in	O
the	O
Linux	B-Application
kernel	O
was	O
marked	O
as	O
orphaned	O
on	O
February	O
18	O
,	O
2010	O
.	O
</s>
<s>
DECnet	B-Protocol
refers	O
to	O
a	O
specific	O
set	O
of	O
hardware	O
and	O
software	O
networking	O
products	O
which	O
implement	O
the	O
DIGITAL	B-Protocol
Network	I-Protocol
Architecture	I-Protocol
(	O
DNA	O
)	O
.	O
</s>
<s>
The	O
DIGITAL	B-Protocol
Network	I-Protocol
Architecture	I-Protocol
has	O
a	O
set	O
of	O
documents	O
which	O
define	O
the	O
network	O
architecture	O
in	O
general	O
,	O
state	O
the	O
specifications	O
for	O
each	O
layer	O
of	O
the	O
architecture	O
,	O
and	O
describe	O
the	O
protocols	B-Protocol
which	O
operate	O
within	O
each	O
layer	O
.	O
</s>
<s>
Although	O
network	B-Protocol
protocol	I-Protocol
analyzer	I-Protocol
tools	I-Protocol
tend	O
to	O
categorize	O
all	O
protocols	B-Protocol
from	O
DIGITAL	O
as	O
"	O
DECnet	B-Protocol
"	O
,	O
strictly	O
speaking	O
,	O
non-routed	O
DIGITAL	O
protocols	B-Protocol
such	O
as	O
LAT	B-General_Concept
,	O
SCS	O
,	O
AMDS	O
,	O
LAST/LAD	O
are	O
not	O
DECnet	B-Protocol
protocols	B-Protocol
and	O
are	O
not	O
part	O
of	O
the	O
DIGITAL	B-Protocol
Network	I-Protocol
Architecture	I-Protocol
.	O
</s>
<s>
To	O
trace	O
the	O
evolution	O
of	O
DECnet	B-Protocol
is	O
to	O
trace	O
the	O
development	O
of	O
DNA	O
.	O
</s>
<s>
DIGITAL	O
published	O
its	O
first	O
DNA	O
specification	O
at	O
about	O
the	O
same	O
time	O
that	O
IBM	O
announced	O
its	O
Systems	B-Architecture
Network	I-Architecture
Architecture	I-Architecture
(	O
SNA	O
)	O
.	O
</s>
<s>
Support	O
limited	O
to	O
two	O
PDP-11s	B-Device
running	O
the	O
RSX-11	B-Application
operating	B-General_Concept
system	I-General_Concept
only	O
,	O
with	O
communication	O
over	O
point-to-point	O
(	O
DDCMP	B-Protocol
)	O
links	O
between	O
nodes	O
.	O
</s>
<s>
Implementations	O
expanded	O
to	O
include	O
RSTS	B-Operating_System
,	O
TOPS-10	B-Operating_System
and	O
TOPS-20	B-Operating_System
with	O
communications	O
between	O
processors	O
still	O
limited	O
to	O
point-to-point	O
links	O
only	O
.	O
</s>
<s>
Introduction	O
of	O
downline	O
loading	O
(	O
MOP	O
)	O
,	O
and	O
file	O
transfer	O
using	O
File	B-Protocol
Access	I-Protocol
Listener	I-Protocol
(	O
FAL	O
)	O
,	O
remote	O
file	O
access	O
using	O
Data	O
Access	O
Protocol	O
(	O
DAP	O
)	O
,	O
task-to-task	O
programming	O
interfaces	O
and	O
network	O
management	O
features	O
.	O
</s>
<s>
Introduction	O
of	O
adaptive	O
routing	O
capability	O
,	O
record	O
access	O
,	O
a	O
network	O
management	O
architecture	O
,	O
and	O
gateways	O
to	O
other	O
types	O
of	O
networks	O
including	O
IBM	O
's	O
SNA	O
and	O
CCITT	O
Recommendation	O
X.25	B-Protocol
.	O
</s>
<s>
MOP	O
:	O
Maintenance	B-Operating_System
Operations	I-Operating_System
Protocol	I-Operating_System
Session	O
SCP	O
:	O
Session	O
Control	O
Protocol	O
Transport	O
NSP	O
:	O
Network	O
Service	O
Protocol	O
Network	O
DRP	O
:	O
DECnet	B-Protocol
Routing	O
Protocol	O
Data	O
link	O
DDCMP	B-Protocol
:	O
Digital	O
Data	O
Communications	O
Message	O
ProtocolEthernet	O
,	O
Token	B-Device
Ring	I-Device
,	O
HDLC	O
,	O
FDDI	B-Protocol
,	O
...	O
</s>
<s>
Physical	O
Ethernet	O
,	O
Token	B-Device
Ring	I-Device
,	O
FDDI	B-Protocol
,	O
...	O
</s>
<s>
Phase	O
IV	O
was	O
released	O
initially	O
to	O
RSX-11	B-Application
and	O
VMS	B-Operating_System
systems	O
,	O
later	O
TOPS-20	B-Operating_System
,	O
TOPS-10	B-Operating_System
,	O
ULTRIX	B-Operating_System
,	O
VAXELN	B-Operating_System
,	O
and	O
RSTS/E	B-Operating_System
gained	O
support	O
.	O
</s>
<s>
Support	O
for	O
networks	O
of	O
up	O
to	O
64,449	O
nodes	O
(	O
63	O
areas	O
of	O
1023	O
nodes	O
)	O
,	O
datalink	O
capabilities	O
expanded	O
beyond	O
DDCMP	B-Protocol
to	O
include	O
Ethernet	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
support	O
as	O
the	O
datalink	O
of	O
choice	O
,	O
expanded	O
adaptive	O
routing	O
capability	O
to	O
include	O
hierarchical	O
routing	O
(	O
areas	O
,	O
level	O
1	O
and	O
level	O
2	O
routers	O
)	O
,	O
VMScluster	B-Operating_System
support	O
(	O
cluster	O
alias	O
)	O
and	O
host	O
services	O
(	O
CTERM	O
)	O
.	O
</s>
<s>
CTERM	O
allowed	O
a	O
user	O
on	O
one	O
computer	O
to	O
log	O
into	O
another	O
computer	O
remotely	O
,	O
performing	O
the	O
same	O
function	O
that	O
Telnet	B-Protocol
does	O
in	O
the	O
TCP/IP	B-Protocol
protocol	I-Protocol
stack	I-Protocol
.	O
</s>
<s>
Digital	O
also	O
released	O
a	O
product	O
called	O
the	O
PATHWORKS	O
client	O
,	O
and	O
more	O
commonly	O
known	O
as	O
the	O
PATHWORKS	O
32	O
client	O
,	O
that	O
implemented	O
much	O
of	O
DECnet	B-Protocol
Phase	O
IV	O
for	O
DOS	B-Device
,	O
and	O
16	O
and	O
32	O
bit	O
Microsoft	B-Application
Windows	I-Application
platforms	O
(	O
all	O
the	O
way	O
through	O
to	O
Windows	O
Server	O
2003	O
)	O
.	O
</s>
<s>
Since	O
the	O
OSI	O
standards	O
were	O
not	O
yet	O
fully	O
developed	O
at	O
the	O
time	O
,	O
many	O
of	O
the	O
Phase	O
IV	O
protocols	B-Protocol
remained	O
proprietary	O
.	O
</s>
<s>
The	O
Ethernet	O
implementation	O
was	O
unusual	O
in	O
that	O
the	O
software	O
changed	O
the	O
physical	O
address	O
of	O
the	O
Ethernet	O
interface	O
on	O
the	O
network	O
to	O
AA-00-04-00-xx-yy	O
where	O
xx-yy	O
reflected	O
the	O
DECnet	B-Protocol
network	B-Protocol
address	I-Protocol
of	O
the	O
host	O
.	O
</s>
<s>
This	O
allowed	O
ARP-less	O
LAN	B-General_Concept
operation	O
because	O
the	O
LAN	B-General_Concept
address	O
could	O
be	O
deduced	O
from	O
the	O
DECnet	B-Protocol
address	O
.	O
</s>
<s>
This	O
precluded	O
connecting	O
two	O
NICs	B-Protocol
from	O
the	O
same	O
DECnet	B-Protocol
node	O
onto	O
the	O
same	O
LAN	B-General_Concept
segment	O
,	O
however	O
.	O
</s>
<s>
The	O
initial	O
implementations	O
released	O
were	O
for	O
VAX/VMS	B-Operating_System
and	O
RSX-11	B-Application
,	O
later	O
this	O
expanded	O
to	O
virtually	O
every	O
operating	B-General_Concept
system	I-General_Concept
DIGITAL	O
ever	O
shipped	O
with	O
the	O
notable	O
exception	O
of	O
RT-11	B-Operating_System
.	O
</s>
<s>
DECnet	B-Protocol
stacks	O
are	O
found	O
on	O
Linux	B-Application
,	O
SunOS	O
and	O
other	O
platforms	O
,	O
and	O
Cisco	O
and	O
other	O
network	O
vendors	O
offer	O
products	O
that	O
can	O
cooperate	O
with	O
and	O
operate	O
within	O
DECnet	B-Protocol
networks	O
.	O
</s>
<s>
Full	O
DECnet	B-Protocol
Phase	O
IV	O
specifications	O
are	O
available	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
that	O
DECnet	B-Protocol
Phase	O
IV	O
was	O
released	O
,	O
the	O
company	O
also	O
released	O
a	O
proprietary	O
protocol	O
called	O
LAT	B-General_Concept
for	O
serial	O
terminal	O
access	O
via	O
Terminal	B-Device
servers	I-Device
.	O
</s>
<s>
LAT	B-General_Concept
shared	O
the	O
OSI	O
physical	O
and	O
datalink	O
layers	B-Application
with	O
DECnet	B-Protocol
and	O
LAT	B-General_Concept
terminal	B-Device
servers	I-Device
used	O
MOP	O
for	O
the	O
server	O
image	O
download	O
and	O
related	O
bootstrap	O
processing	O
.	O
</s>
<s>
Enhancements	O
made	O
to	O
DECnet	B-Protocol
Phase	O
IV	O
eventually	O
became	O
known	O
as	O
DECnet	B-Protocol
Phase	O
IV+	O
,	O
although	O
systems	O
running	O
this	O
protocol	O
remained	O
completely	O
interoperable	O
with	O
DECnet	B-Protocol
Phase	O
IV	O
systems	O
.	O
</s>
<s>
Transparent	O
transport	O
level	O
links	O
to	O
TCP/IP	B-Protocol
were	O
added	O
via	O
the	O
IETF	O
RFC	O
1006	O
(	O
OSI	O
over	O
IP	O
)	O
and	O
RFC	O
1859	O
(	O
NSP	O
over	O
IP	O
)	O
standards	O
(	O
see	O
diagram	O
)	O
.	O
</s>
<s>
It	O
was	O
later	O
renamed	O
DECnet/OSI	O
to	O
emphasize	O
its	O
OSI	O
interconnectibility	O
,	O
and	O
subsequently	O
DECnet-Plus	O
as	O
TCP/IP	B-Protocol
protocols	I-Protocol
were	O
incorporated	O
.	O
</s>
<s>
DEC	O
's	O
internal	O
corporate	O
network	O
was	O
a	O
DECnet	B-Protocol
network	O
called	O
Easynet	O
,	O
which	O
had	O
evolved	O
from	O
DEC	O
's	O
Engineering	O
Net	O
(	O
E-NET	O
)	O
.	O
</s>
<s>
DECnet	B-Protocol
was	O
used	O
at	O
various	O
scientific	O
research	O
centers	O
which	O
linked	O
their	O
networks	O
to	O
form	O
an	O
international	O
network	O
called	O
the	O
DECnet	B-Protocol
Internet	O
.	O
</s>
<s>
In	O
December	O
1988	O
,	O
VAX/VMS	B-Operating_System
hosts	O
on	O
the	O
DECnet	B-Protocol
Internet	O
were	O
attacked	O
by	O
the	O
Father	O
Christmas	O
worm	O
.	O
</s>
<s>
CCNET	O
(	O
Computer	O
Center	O
Network	O
)	O
was	O
a	O
DECnet	B-Protocol
network	O
that	O
connected	O
the	O
campuses	O
of	O
various	O
universities	O
in	O
the	O
eastern	O
regions	O
of	O
the	O
United	O
States	O
during	O
the	O
1980s	O
.	O
</s>
<s>
Hobbyist	O
DECnet	B-Protocol
networks	O
have	O
been	O
in	O
use	O
during	O
the	O
21st	O
century	O
.	O
</s>
