<s>
In	O
computing	O
,	O
the	O
Distributed	B-Operating_System
Computing	I-Operating_System
Environment	I-Operating_System
(	O
DCE	O
)	O
software	O
system	O
was	O
developed	O
in	O
the	O
early	O
1990s	O
from	O
the	O
work	O
of	O
the	O
Open	B-Application
Software	I-Application
Foundation	I-Application
(	O
OSF	B-Operating_System
)	O
,	O
a	O
consortium	O
(	O
founded	O
in	O
1988	O
)	O
that	O
included	O
Apollo	O
Computer	O
(	O
part	O
of	O
Hewlett-Packard	O
from	O
1989	O
)	O
,	O
IBM	O
,	O
Digital	O
Equipment	O
Corporation	O
,	O
and	O
others	O
.	O
</s>
<s>
The	O
DCE	O
supplies	O
a	O
framework	B-Architecture
and	O
a	O
toolkit	O
for	O
developing	O
client/server	B-Operating_System
applications	O
.	O
</s>
<s>
The	O
framework	B-Architecture
includes	O
:	O
</s>
<s>
Open	B-Application
Software	I-Application
Foundation	I-Application
(	O
OSF	B-Operating_System
)	O
came	O
about	O
to	O
a	O
large	O
degree	O
as	O
part	O
of	O
the	O
Unix	O
wars	O
of	O
the	O
1980s	O
.	O
</s>
<s>
After	O
Sun	O
Microsystems	O
and	O
AT&T	O
Corporation	O
worked	O
together	O
to	O
produce	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
Release	I-Operating_System
4	I-Operating_System
(	O
SVR4	O
)	O
and	O
refused	O
to	O
commit	O
to	O
fair	O
and	O
open	O
licensing	O
of	O
Unix	O
source	O
code	O
,	O
many	O
of	O
the	O
other	O
Unix	O
vendors	O
felt	O
their	O
own	O
market	O
opportunities	O
were	O
unduly	O
disadvantaged	O
.	O
</s>
<s>
The	O
Distributed	B-Operating_System
Computing	I-Operating_System
Environment	I-Operating_System
is	O
a	O
component	O
of	O
the	O
OSF	B-Operating_System
offerings	O
,	O
along	O
with	O
Motif	O
,	O
OSF/1	B-Operating_System
and	O
the	O
Distributed	O
Management	O
Environment	O
(	O
DME	O
)	O
.	O
</s>
<s>
As	O
part	O
of	O
the	O
formation	O
of	O
OSF	B-Operating_System
,	O
various	O
members	O
contributed	O
many	O
of	O
their	O
ongoing	O
research	O
projects	O
as	O
well	O
as	O
their	O
commercial	O
products	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
network	O
computing	O
was	O
quite	O
popular	O
,	O
and	O
many	O
of	O
the	O
companies	O
involved	O
were	O
working	O
on	O
similar	O
RPC-based	O
systems	O
.	O
</s>
<s>
By	O
integrating	O
security	O
,	O
RPC	B-Operating_System
and	O
other	O
distributed	O
services	O
on	O
a	O
single	O
"	O
official	O
"	O
distributed	B-Operating_System
computing	I-Operating_System
environment	I-Operating_System
,	O
OSF	B-Operating_System
could	O
offer	O
a	O
major	O
advantage	O
over	O
SVR4	O
,	O
allowing	O
any	O
DCE-supporting	O
system	O
(	O
namely	O
OSF/1	B-Operating_System
)	O
to	O
interoperate	O
in	O
a	O
larger	O
network	O
.	O
</s>
<s>
DCE/RPC	B-General_Concept
was	O
derived	O
from	O
the	O
Network	B-Protocol
Computing	I-Protocol
System	I-Protocol
(	O
NCS	O
)	O
created	O
at	O
Apollo	O
Computer	O
.	O
</s>
<s>
DCE/DFS	B-Protocol
was	O
based	O
on	O
the	O
Andrew	B-Application
File	I-Application
System	I-Application
(	O
AFS	O
)	O
originally	O
developed	O
at	O
Carnegie	O
Mellon	O
University	O
.	O
</s>
<s>
The	O
authentication	O
system	O
was	O
based	O
on	O
Kerberos	B-Protocol
,	O
and	O
the	O
authorization	O
system	O
based	O
on	O
Access	O
Control	O
Lists	O
(	O
ACLs	O
)	O
.	O
</s>
<s>
By	O
combining	O
these	O
features	O
,	O
DCE	O
offers	O
a	O
fairly	O
complete	O
C-based	O
system	O
for	O
network	O
computing	O
.	O
</s>
<s>
Any	O
machine	O
on	O
the	O
network	O
can	O
authenticate	O
its	O
users	O
,	O
gain	O
access	O
to	O
resources	O
,	O
and	O
then	O
call	O
them	O
remotely	O
using	O
a	O
single	O
integrated	O
API	B-Application
.	O
</s>
<s>
The	O
rise	O
of	O
the	O
Internet	O
,	O
Java	B-Language
and	O
web	O
services	O
stole	O
much	O
of	O
DCE	O
's	O
mindshare	O
through	O
the	O
mid-to-late	O
1990s	O
,	O
and	O
competing	O
systems	O
such	O
as	O
CORBA	B-Architecture
muddied	O
the	O
waters	O
as	O
well	O
.	O
</s>
<s>
One	O
of	O
the	O
major	O
uses	O
of	O
DCE	O
today	O
is	O
Microsoft	O
's	O
DCOM	B-Operating_System
and	O
ODBC	B-Application
systems	O
,	O
which	O
use	O
DCE/RPC	B-General_Concept
(	O
in	O
MSRPC	B-General_Concept
)	O
as	O
their	O
network	O
transport	O
layer	O
.	O
</s>
<s>
OSF	B-Operating_System
and	O
its	O
projects	O
eventually	O
became	O
part	O
of	O
The	B-Application
Open	I-Application
Group	I-Application
,	O
which	O
released	O
DCE	O
1.2.2	O
under	O
a	O
free	B-License
software	I-License
license	I-License
(	O
the	O
LGPL	B-Application
)	O
on	O
12	O
January	O
2005	O
.	O
</s>
<s>
DCE	O
1.1	O
was	O
available	O
much	O
earlier	O
under	O
the	O
OSF	B-Operating_System
BSD	O
license	O
,	O
and	O
resulted	O
in	O
FreeDCE	B-Operating_System
being	O
available	O
since	O
2000	O
.	O
</s>
<s>
FreeDCE	B-Operating_System
contains	O
an	O
implementation	O
of	O
DCOM	B-Operating_System
.	O
</s>
<s>
One	O
of	O
the	O
major	O
implementations	O
of	O
DCE	O
was	O
Encina	B-Application
,	O
originally	O
developed	O
by	O
Transarc	O
(	O
who	O
were	O
acquired	O
by	O
IBM	O
)	O
.	O
</s>
<s>
IBM	O
used	O
Encina	B-Application
as	O
a	O
foundation	O
to	O
port	O
its	O
primary	O
mainframe	O
transaction	O
processing	O
system	O
(	O
CICS	B-Application
)	O
to	O
non-mainframe	O
platforms	O
,	O
as	O
IBM	B-Application
TXSeries	I-Application
.	O
</s>
<s>
(	O
However	O
,	O
later	O
versions	O
of	O
TXSeries	B-Application
have	O
removed	O
the	O
Encina	B-Application
component	O
.	O
)	O
</s>
<s>
Modern	O
DCE	O
implementations	O
such	O
as	O
IBM	O
's	O
are	O
fully	O
capable	O
of	O
interoperating	O
with	O
Kerberos	B-Protocol
as	O
the	O
security	O
server	O
,	O
LDAP	O
for	O
the	O
CDS	O
and	O
the	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
implementations	O
for	O
the	O
time	O
server	O
.	O
</s>
<s>
While	O
it	O
is	O
possible	O
to	O
implement	O
a	O
distributed	B-Protocol
file	I-Protocol
system	I-Protocol
using	O
the	O
DCE	O
underpinnings	O
by	O
adding	O
filenames	O
to	O
the	O
CDS	O
and	O
defining	O
the	O
appropriate	O
ACLs	O
on	O
them	O
,	O
this	O
is	O
not	O
user-friendly	O
.	O
</s>
<s>
DCE/DFS	B-Protocol
is	O
a	O
DCE-based	O
application	O
which	O
provides	O
a	O
distributed	O
filesystem	O
on	O
DCE	O
.	O
</s>
<s>
DCE/DFS	B-Protocol
can	O
support	O
replicas	O
of	O
a	O
fileset	O
(	O
the	O
DCE/DFS	B-Protocol
equivalent	O
of	O
a	O
filesystem	O
)	O
on	O
multiple	O
DFS	B-Protocol
servers	O
-	O
there	O
is	O
one	O
read-write	O
copy	O
and	O
zero	O
or	O
more	O
read	O
only	O
copies	O
.	O
</s>
<s>
In	O
addition	O
,	O
DCE/DFS	B-Protocol
also	O
supports	O
what	O
are	O
called	O
"	O
backup	O
"	O
filesets	O
,	O
which	O
if	O
defined	O
for	O
a	O
fileset	O
are	O
capable	O
of	O
storing	O
a	O
version	O
of	O
the	O
fileset	O
as	O
it	O
was	O
prior	O
to	O
the	O
last	O
replication	O
.	O
</s>
<s>
DCE/DFS	B-Protocol
is	O
believed	O
to	O
be	O
the	O
world	O
's	O
only	O
distributed	O
filesystem	O
that	O
correctly	O
implements	O
the	O
full	O
POSIX	O
filesystem	O
semantics	O
,	O
including	O
byte	O
range	O
locking	O
.	O
</s>
<s>
DCE/DFS	B-Protocol
was	O
sufficiently	O
reliable	O
and	O
stable	O
to	O
be	O
utilised	O
by	O
IBM	O
to	O
run	O
the	O
back-end	O
filesystem	O
for	O
the	O
1996	O
Olympics	O
web	O
site	O
,	O
seamlessly	O
and	O
automatically	O
distributed	O
and	O
edited	O
worldwide	O
in	O
different	O
time	O
zones	O
.	O
</s>
