<s>
A	O
time	B-Protocol
server	I-Protocol
is	O
a	O
server	B-Application
computer	I-Application
that	O
reads	O
the	O
actual	O
time	O
from	O
a	O
reference	O
clock	O
and	O
distributes	O
this	O
information	O
to	O
its	O
clients	O
using	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
The	O
time	B-Protocol
server	I-Protocol
may	O
be	O
a	O
local	O
network	B-Protocol
time	I-Protocol
server	I-Protocol
or	O
an	O
internet	B-Protocol
time	I-Protocol
server	I-Protocol
.	O
</s>
<s>
The	O
most	O
important	O
and	O
widely	O
used	O
protocol	O
for	O
distributing	O
and	O
synchronising	O
time	O
over	O
the	O
Internet	O
is	O
the	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
NTP	O
)	O
,	O
though	O
other	O
less-popular	O
or	O
outdated	O
time	O
protocols	O
continue	O
in	O
use	O
.	O
</s>
<s>
The	O
time	O
reference	O
used	O
by	O
a	O
time	B-Protocol
server	I-Protocol
could	O
be	O
another	O
time	B-Protocol
server	I-Protocol
on	O
the	O
network	O
or	O
the	O
Internet	O
,	O
a	O
connected	O
radio	O
clock	O
or	O
an	O
atomic	O
clock	O
.	O
</s>
<s>
Time	B-Protocol
servers	I-Protocol
are	O
sometimes	O
multi-purpose	O
network	B-Application
servers	I-Application
,	O
dedicated	O
network	B-Application
servers	I-Application
,	O
or	O
dedicated	O
devices	O
.	O
</s>
<s>
All	O
a	O
dedicated	O
time	B-Protocol
server	I-Protocol
does	O
is	O
provide	O
accurate	O
time	O
.	O
</s>
<s>
An	O
existing	O
network	B-Application
server	I-Application
(	O
e.g.	O
</s>
<s>
a	O
file	O
server	B-Application
)	O
can	O
become	O
a	O
time	B-Protocol
server	I-Protocol
with	O
additional	O
software	O
.	O
</s>
<s>
The	O
NTP	O
homepage	O
provides	O
a	O
free	O
and	O
widely	O
used	O
reference	O
implementation	O
of	O
the	O
NTP	B-Protocol
server	I-Protocol
and	O
client	O
for	O
many	O
popular	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
The	O
other	O
choice	O
is	O
a	O
dedicated	O
time	B-Protocol
server	I-Protocol
device	O
.	O
</s>
<s>
The	O
term	O
"	O
stratum	O
"	O
is	O
used	O
to	O
label	O
the	O
closeness	O
to	O
a	O
central	O
or	O
high	O
quality	O
time	B-Protocol
server	I-Protocol
.	O
</s>
<s>
The	O
stratum	O
indicates	O
the	O
place	O
of	O
a	O
particular	O
time	B-Protocol
server	I-Protocol
in	O
a	O
hierarchy	O
of	O
servers	O
.	O
</s>
<s>
Some	O
time	O
clients	O
will	O
reject	O
a	O
time	O
update	O
from	O
a	O
server	B-Application
whose	O
stratum	O
is	O
too	O
high	O
,	O
and	O
most	O
will	O
prefer	O
low	O
strata	O
time	O
sources	O
to	O
higher	O
ones	O
.	O
</s>
<s>
This	O
can	O
be	O
a	O
pitfall	O
for	O
administrators	O
setting	O
up	O
an	O
in-house	O
time	B-Protocol
server	I-Protocol
with	O
no	O
true	O
time	O
source	O
.	O
</s>
