<s>
OpenLDAP	B-Language
is	O
a	O
free	B-Application
,	O
open-source	B-Application
implementation	O
of	O
the	O
Lightweight	B-Protocol
Directory	I-Protocol
Access	I-Protocol
Protocol	I-Protocol
(	O
LDAP	B-Protocol
)	O
developed	O
by	O
the	O
OpenLDAP	B-Language
Project	O
.	O
</s>
<s>
It	O
is	O
released	O
under	O
its	O
own	O
BSD-style	O
license	O
called	O
the	O
OpenLDAP	B-Language
Public	O
License	O
.	O
</s>
<s>
LDAP	B-Protocol
is	O
a	O
platform-independent	B-Operating_System
protocol	O
.	O
</s>
<s>
Several	O
common	O
Linux	B-Application
distributions	O
include	O
OpenLDAP	B-Language
Software	O
for	O
LDAP	B-Protocol
support	O
.	O
</s>
<s>
The	O
software	O
also	O
runs	O
on	O
BSD-variants	O
,	O
as	O
well	O
as	O
AIX	B-Application
,	O
Android	B-Application
,	O
HP-UX	B-Application
,	O
macOS	B-Application
,	O
OpenVMS	B-Operating_System
,	O
Solaris	B-Application
,	O
Microsoft	B-Application
Windows	I-Application
(	O
NT	O
and	O
derivatives	O
,	O
e.g.	O
</s>
<s>
)	O
,	O
and	O
z/OS	B-Application
.	O
</s>
<s>
The	O
OpenLDAP	B-Language
project	O
was	O
started	O
in	O
1998	O
by	O
Kurt	O
Zeilenga	O
.	O
</s>
<s>
The	O
project	O
started	O
by	O
cloning	O
the	O
LDAP	B-Protocol
reference	O
source	O
from	O
the	O
University	O
of	O
Michigan	O
where	O
a	O
long-running	O
project	O
had	O
supported	O
development	O
and	O
evolution	O
of	O
the	O
LDAP	B-Protocol
protocol	O
until	O
that	O
project	O
's	O
final	O
release	O
in	O
1996	O
.	O
</s>
<s>
,	O
the	O
OpenLDAP	B-Language
project	O
has	O
four	O
core	O
team	O
members	O
:	O
Howard	O
Chu	O
(	O
chief	O
architect	O
)	O
,	O
Quanah	O
Gibson-Mount	O
,	O
Hallvard	O
Furuseth	O
,	O
and	O
Kurt	O
Zeilenga	O
.	O
</s>
<s>
OpenLDAP	B-Language
has	O
four	O
main	O
components	O
:	O
</s>
<s>
slapd	B-Application
–	O
stand-alone	O
LDAP	B-Protocol
daemon	B-Operating_System
and	O
associated	O
modules	O
and	O
tools	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
OpenLDAP	B-Language
Project	O
is	O
home	O
to	O
a	O
number	O
of	O
subprojects	O
:	O
</s>
<s>
Historically	O
the	O
OpenLDAP	B-Language
server	O
(	O
slapd	B-Application
,	O
the	O
Standalone	O
LDAP	B-Protocol
Daemon	B-Operating_System
)	O
architecture	O
was	O
split	O
between	O
a	O
frontend	O
that	O
handles	O
network	O
access	O
and	O
protocol	O
processing	O
,	O
and	O
a	O
backend	O
that	O
deals	O
strictly	O
with	O
data	O
storage	O
.	O
</s>
<s>
This	O
split	O
design	O
was	O
a	O
feature	O
of	O
the	O
original	O
University	O
of	O
Michigan	O
code	O
written	O
in	O
1996	O
and	O
carried	O
on	O
in	O
all	O
subsequent	O
OpenLDAP	B-Language
releases	O
.	O
</s>
<s>
The	O
slapd	B-Application
server	O
can	O
use	O
arbitrarily	O
many	O
backends	O
at	O
once	O
,	O
and	O
can	O
have	O
arbitrarily	O
many	O
instances	O
of	O
each	O
backend	O
(	O
i.e.	O
,	O
arbitrarily	O
many	O
databases	O
)	O
active	O
at	O
once	O
.	O
</s>
<s>
Currently	O
17	O
different	O
backends	O
are	O
provided	O
in	O
the	O
OpenLDAP	B-Language
distribution	O
,	O
and	O
various	O
third	O
parties	O
are	O
known	O
to	O
maintain	O
other	O
backends	O
independently	O
.	O
</s>
<s>
back-bdb	O
:	O
the	O
first	O
transactional	O
backend	O
for	O
OpenLDAP	B-Language
,	O
built	O
on	O
Berkeley	B-Language
DB	I-Language
,	O
removed	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
back-hdb	O
:	O
a	O
variant	O
of	O
back-bdb	O
that	O
is	O
fully	O
hierarchical	O
and	O
supports	O
subtree	O
renames	O
,	O
removed	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
back-ndb	O
:	O
a	O
transactional	O
backend	O
built	O
on	O
MySQL	O
's	O
NDB	O
cluster	O
engine	O
,	O
removed	O
with	O
OpenLDAP	B-Language
2.6	O
.	O
</s>
<s>
back-wiredtiger	O
:	O
an	O
experimental	O
transactional	O
backend	O
built	O
on	O
WiredTiger	B-Application
,	O
introduced	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
back-asyncmeta	O
:	O
an	O
asynchronous	O
proxy	O
with	O
meta-directory	O
features	O
,	O
introduced	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
back-sql	O
:	O
talks	O
to	O
arbitrary	O
SQL	O
databases	O
,	O
deprecated	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
back-perl	O
:	O
invokes	O
arbitrary	O
perl	O
modules	O
in	O
response	O
to	O
LDAP	B-Protocol
requests	O
,	O
deprecated	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
back-shell	O
:	O
invokes	O
shell	O
scripts	O
for	O
LDAP	B-Protocol
requests	O
,	O
removed	O
with	O
OpenLDAP	B-Language
2.5	O
.	O
</s>
<s>
Some	O
backends	O
available	O
in	O
older	O
OpenLDAP	B-Language
releases	O
have	O
been	O
retired	O
from	O
use	O
,	O
most	O
notably	O
back-ldbm	O
which	O
was	O
inherited	O
from	O
the	O
original	O
UMich	O
code	O
,	O
and	O
back-tcl	O
which	O
was	O
similar	O
to	O
back-perl	O
and	O
back-shell	O
.	O
</s>
<s>
In	O
effect	O
the	O
slapd	B-Application
server	O
becomes	O
an	O
RPC	O
engine	O
with	O
a	O
compact	O
,	O
well-defined	O
and	O
ubiquitous	O
API	O
.	O
</s>
<s>
Ordinarily	O
an	O
LDAP	B-Protocol
request	O
is	O
received	O
by	O
the	O
frontend	O
,	O
decoded	O
,	O
and	O
then	O
passed	O
to	O
a	O
backend	O
for	O
processing	O
.	O
</s>
<s>
When	O
the	O
backend	O
completes	O
a	O
request	O
,	O
it	O
returns	O
a	O
result	O
to	O
the	O
frontend	O
,	O
which	O
then	O
sends	O
the	O
result	O
to	O
the	O
LDAP	B-Protocol
client	O
.	O
</s>
<s>
Overlays	O
have	O
complete	O
access	O
to	O
the	O
slapd	B-Application
internal	O
APIs	O
,	O
and	O
so	O
can	O
invoke	O
anything	O
the	O
frontend	O
or	O
other	O
backends	O
could	O
perform	O
.	O
</s>
<s>
Since	O
the	O
introduction	O
of	O
the	O
overlay	O
feature	O
in	O
OpenLDAP	B-Language
2.2	O
many	O
new	O
overlays	O
have	O
been	O
contributed	O
from	O
the	O
OpenLDAP	B-Language
community	O
.	O
</s>
<s>
Currently	O
there	O
are	O
25	O
overlays	O
in	O
the	O
core	O
OpenLDAP	B-Language
distribution	O
,	O
with	O
another	O
24	O
overlays	O
in	O
the	O
user-contributed	O
code	O
section	O
,	O
and	O
more	O
awaiting	O
approval	O
for	O
inclusion	O
.	O
</s>
<s>
ppolicy	O
:	O
LDAP	B-Protocol
Password	O
Policy	O
–	O
password	O
quality	O
,	O
expiration	O
,	O
etc	O
.	O
</s>
<s>
nssov	O
:	O
Answer	O
NSS	O
and	O
PAM	O
requests	O
directly	O
in	O
slapd	B-Application
,	O
replaces	O
nss-ldap	O
and	O
pam-ldap	O
.	O
</s>
<s>
Backends	O
were	O
typically	O
built	O
into	O
the	O
slapd	B-Application
binary	O
,	O
but	O
they	O
may	O
also	O
be	O
built	O
as	O
dynamically	O
loaded	O
modules	O
,	O
and	O
overlays	O
are	O
usually	O
built	O
as	O
dynamic	O
modules	O
.	O
</s>
<s>
In	O
addition	O
,	O
slapd	B-Application
supports	O
dynamic	O
modules	O
for	O
implementing	O
new	O
LDAP	B-Protocol
syntaxes	O
,	O
matching	O
rules	O
,	O
controls	O
,	O
and	O
extended	O
operations	O
,	O
as	O
well	O
as	O
for	O
implementing	O
custom	O
access	O
control	O
mechanisms	O
and	O
password	O
hashing	O
mechanisms	O
.	O
</s>
<s>
OpenLDAP	B-Language
also	O
supports	O
SLAPI	O
,	O
the	O
plugin	O
architecture	O
used	O
by	O
Sun	O
and	O
Netscape/Fedora/Red	O
Hat	O
.	O
</s>
<s>
In	O
current	O
releases	O
,	O
the	O
SLAPI	O
framework	O
is	O
implemented	O
inside	O
a	O
slapd	B-Application
overlay	O
.	O
</s>
<s>
While	O
many	O
plugins	O
written	O
for	O
Sun/Netscape/Fedora/Red	O
Hat	O
are	O
compatible	O
with	O
OpenLDAP	B-Language
,	O
very	O
few	O
members	O
of	O
the	O
OpenLDAP	B-Language
community	O
use	O
SLAPI	O
.	O
</s>
<s>
Currently	O
includes	O
Kerberos	B-Protocol
,	O
Netscape	O
,	O
RADIUS	B-Protocol
,	O
and	O
SHA-2	B-Algorithm
.	O
</s>
<s>
The	O
major	O
(	O
functional	O
)	O
releases	O
of	O
OpenLDAP	B-Language
Software	O
include	O
:	O
</s>
<s>
OpenLDAP	B-Language
Version	O
1	O
was	O
a	O
general	O
clean-up	O
of	O
the	O
last	O
release	O
from	O
the	O
University	O
of	O
Michigan	O
project	O
(	O
release	O
3.3	O
)	O
,	O
and	O
consolidation	O
of	O
additional	O
changes	O
.	O
</s>
<s>
OpenLDAP	B-Language
Version	O
2.0	O
,	O
released	O
in	O
August	O
2000	O
,	O
included	O
major	O
enhancements	O
including	O
LDAP	B-Protocol
version	O
3	O
(	O
LDAPv3	O
)	O
support	O
,	O
Internet	B-Protocol
Protocol	I-Protocol
version	I-Protocol
6	I-Protocol
(	O
IPv6	B-Protocol
)	O
support	O
,	O
and	O
numerous	O
other	O
enhancements	O
.	O
</s>
<s>
OpenLDAP	B-Language
Version	O
2.1	O
,	O
released	O
in	O
June	O
2002	O
,	O
included	O
the	O
transactional	O
database	O
backend	O
(	O
based	O
on	O
Berkeley	B-Language
Database	I-Language
or	O
BDB	O
)	O
,	O
Simple	O
Authentication	O
and	O
Security	O
Layer	O
(	O
SASL	O
)	O
support	O
,	O
and	O
Meta	O
,	O
Monitor	O
,	O
and	O
Virtual	O
experimental	O
backends	O
.	O
</s>
<s>
OpenLDAP	B-Language
Version	O
2.2	O
,	O
released	O
in	O
December	O
2003	O
,	O
included	O
the	O
LDAP	B-Protocol
"	O
sync	O
"	O
Engine	O
with	O
replication	O
support	O
(	O
syncrepl	O
)	O
,	O
the	O
overlay	O
interface	O
,	O
and	O
numerous	O
database	O
and	O
RFC-related	O
functional	O
enhancements	O
.	O
</s>
<s>
OpenLDAP	B-Language
Version	O
2.3	O
,	O
released	O
in	O
June	O
2005	O
,	O
included	O
the	O
Configuration	O
Backend	O
(	O
dynamic	O
configuration	O
)	O
,	O
additional	O
overlays	O
including	O
RFC-compliant	O
Password	O
Policy	O
software	O
,	O
and	O
numerous	O
additional	O
enhancements	O
.	O
</s>
<s>
OpenLDAP	B-Language
Version	O
2.4	O
,	O
released	O
in	O
October	O
2007	O
,	O
introduced	O
N-way	O
MultiMaster	B-Operating_System
replication	I-Operating_System
,	O
Stand-by	O
master	O
,	O
and	O
the	O
ability	O
to	O
delete	O
and	O
modify	O
Schema	O
elements	O
on	O
the	O
fly	O
,	O
plus	O
many	O
more	O
.	O
</s>
<s>
OpenLDAP	B-Language
Version	O
2.5	O
,	O
released	O
in	O
April	O
2021	O
,	O
introduced	O
the	O
LDAP	B-Protocol
load	O
balancing	O
proxy	O
server	O
,	O
LDAP	B-Protocol
transaction	O
support	O
,	O
HA	O
proxy	O
protocol	O
v2	O
support	O
,	O
plus	O
much	O
more	O
.	O
</s>
<s>
OpenLDAP	B-Language
supports	O
replication	O
using	O
Content	O
Synchronization	O
as	O
specified	O
in	O
RFC	O
4533	O
.	O
</s>
<s>
Additional	O
enhancements	O
have	O
been	O
implemented	O
to	O
support	O
multi-master	B-Operating_System
replication	I-Operating_System
.	O
</s>
<s>
In	O
the	O
OpenLDAP	B-Language
implementation	O
of	O
the	O
RFC	O
4533	O
,	O
this	O
cookie	O
includes	O
the	O
latest	O
CSN	O
that	O
has	O
been	O
received	O
from	O
the	O
provider	O
(	O
called	O
the	O
contextCSN	O
)	O
.	O
</s>
<s>
The	O
log	O
entries	O
are	O
recorded	O
using	O
the	O
LDAP	B-Protocol
Log	O
Schema	O
.	O
</s>
