<s>
The	O
Network	B-Operating_System
Information	I-Operating_System
Service	I-Operating_System
,	O
or	O
NIS	O
(	O
originally	O
called	O
Yellow	B-Operating_System
Pages	I-Operating_System
or	O
YP	O
)	O
,	O
is	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
directory	O
service	O
protocol	O
for	O
distributing	B-Architecture
system	O
configuration	O
data	O
such	O
as	O
user	O
and	O
host	B-Protocol
names	I-Protocol
between	O
computers	O
on	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
Sun	O
Microsystems	O
developed	O
the	O
NIS	O
;	O
the	O
technology	O
is	O
licensed	B-License
to	O
virtually	O
all	O
other	O
Unix	B-Application
vendors	O
.	O
</s>
<s>
Because	O
British	O
Telecom	O
PLC	O
owned	O
the	O
name	O
"	O
Yellow	B-Operating_System
Pages	I-Operating_System
"	O
as	O
a	O
registered	O
trademark	O
in	O
the	O
United	O
Kingdom	O
for	O
its	O
paper-based	O
,	O
commercial	O
telephone	O
directory	O
,	O
Sun	O
changed	O
the	O
name	O
of	O
its	O
system	O
to	O
NIS	O
,	O
though	O
all	O
the	O
commands	O
and	O
functions	O
still	O
start	O
with	O
"	O
yp	O
"	O
.	O
</s>
<s>
A	O
NIS/YP	O
system	O
maintains	O
and	O
distributes	O
a	O
central	O
directory	O
of	O
user	O
and	O
group	O
information	O
,	O
hostnames	B-Protocol
,	O
e-mail	O
aliases	O
and	O
other	O
text-based	O
tables	O
of	O
information	O
in	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
For	O
example	O
,	O
in	O
a	O
common	O
UNIX	B-Application
environment	O
,	O
the	O
list	O
of	O
users	O
for	O
identification	O
is	O
placed	O
in	O
and	O
secret	O
authentication	O
hashes	B-Algorithm
in	O
.	O
</s>
<s>
NIS	O
adds	O
another	O
"	O
global	O
"	O
user	O
list	O
which	O
is	O
used	O
for	O
identifying	O
users	O
on	O
any	O
client	B-Protocol
of	O
the	O
NIS	O
domain	O
.	O
</s>
<s>
Administrators	O
have	O
the	O
ability	O
to	O
configure	O
NIS	O
to	O
serve	O
password	O
data	O
to	O
outside	O
processes	O
to	O
authenticate	O
users	O
using	O
various	O
versions	O
of	O
the	O
Unix	B-Application
crypt(3 )	O
hash	B-Algorithm
algorithms	O
.	O
</s>
<s>
However	O
,	O
in	O
such	O
cases	O
,	O
any	O
NIS(0307 )	O
client	B-Protocol
can	O
retrieve	O
the	O
entire	O
password	O
database	O
for	O
offline	O
inspection	O
.	O
</s>
<s>
Sun	O
introduced	O
NIS+	O
as	O
part	O
of	O
Solaris	B-Application
2	I-Application
in	O
1992	O
,	O
with	O
the	O
intention	O
for	O
it	O
to	O
eventually	O
supersede	O
NIS	O
.	O
</s>
<s>
NIS+	O
has	O
been	O
removed	O
from	O
Solaris	B-Application
11	I-Application
.	O
</s>
<s>
As	O
a	O
result	O
,	O
many	O
users	O
choose	O
to	O
stick	O
with	O
NIS	O
,	O
and	O
over	O
time	O
other	O
modern	O
and	O
secure	O
distributed	O
directory	O
systems	O
,	O
most	O
notably	O
Lightweight	B-Protocol
Directory	I-Protocol
Access	I-Protocol
Protocol	I-Protocol
(	O
LDAP	B-Protocol
)	O
,	O
came	O
to	O
replace	O
it	O
.	O
</s>
<s>
For	O
example	O
,	O
slapd	B-Application
(	O
the	O
standalone	O
LDAP	B-Protocol
daemon	B-Operating_System
)	O
generally	O
runs	O
as	O
a	O
non-root	O
user	O
,	O
and	O
SASL-based	O
encryption	O
of	O
LDAP	B-Protocol
traffic	O
is	O
natively	O
supported	O
.	O
</s>
<s>
On	O
large	O
LANs	B-General_Concept
,	O
DNS	B-Protocol
servers	I-Protocol
may	O
provide	O
better	O
nameserver	B-Protocol
functionality	O
than	O
NIS	O
or	O
LDAP	B-Protocol
can	O
provide	O
,	O
leaving	O
just	O
site-wide	O
identification	O
information	O
for	O
NIS	O
master	O
and	O
slave	O
systems	O
to	O
serve	O
.	O
</s>
<s>
However	O
,	O
some	O
functionssuch	O
as	O
the	O
distribution	O
of	O
netmask	O
information	O
to	O
clients	O
,	O
as	O
well	O
as	O
the	O
maintenance	O
of	O
e-mail	O
aliasesmay	O
still	O
be	O
performed	O
by	O
NIS	O
or	O
LDAP	B-Protocol
.	O
</s>
<s>
NIS	O
maintains	O
an	O
NFS	B-Protocol
database	O
information	O
file	O
as	O
well	O
as	O
so	O
called	O
maps	O
.	O
</s>
