<s>
A	O
news	B-Application
server	I-Application
is	O
a	O
collection	O
of	O
software	O
used	O
to	O
handle	O
Usenet	B-Application
articles	O
.	O
</s>
<s>
It	O
may	O
also	O
refer	O
to	O
a	O
computer	O
itself	O
which	O
is	O
primarily	O
or	O
solely	O
used	O
for	O
handling	O
Usenet	B-Application
.	O
</s>
<s>
Access	O
to	O
Usenet	B-Application
is	O
only	O
available	O
through	O
news	B-Application
server	I-Application
providers	O
.	O
</s>
<s>
End	O
users	O
often	O
use	O
the	O
term	O
"	O
posting	O
"	O
to	O
refer	O
to	O
a	O
single	O
message	O
or	O
file	O
posted	O
to	O
Usenet	B-Application
.	O
</s>
<s>
Typically	O
through	O
the	O
use	O
of	O
numbered	O
Subject	O
:	O
headers	O
,	O
the	O
multiple-article	O
postings	O
are	O
automatically	O
reassembled	O
into	O
a	O
single	O
unit	O
by	O
the	O
newsreader	B-Protocol
.	O
</s>
<s>
Each	O
news	O
article	O
contains	O
a	O
complete	O
set	O
of	O
header	O
lines	O
,	O
but	O
in	O
common	O
use	O
the	O
term	O
"	O
headers	O
"	O
is	O
also	O
used	O
when	O
referring	O
to	O
the	O
News	B-Application
Overview	I-Application
database	O
.	O
</s>
<s>
The	O
overview	O
is	O
a	O
list	O
of	O
the	O
most	O
frequently	O
used	O
headers	O
,	O
and	O
additional	O
information	O
such	O
as	O
article	O
sizes	O
,	O
typically	O
retrieved	O
by	O
the	O
client	O
software	O
using	O
the	O
NNTP	B-Protocol
command	O
.	O
</s>
<s>
Overviews	O
make	O
reading	O
a	O
newsgroup	B-Application
faster	O
for	O
both	O
the	O
client	O
and	O
server	O
by	O
eliminating	O
the	O
need	O
to	O
open	O
each	O
individual	O
article	O
to	O
present	O
them	O
in	O
list	O
form	O
.	O
</s>
<s>
If	O
non-overview	O
headers	O
are	O
required	O
,	O
such	O
as	O
for	O
when	O
using	O
a	O
kill	B-Application
file	I-Application
,	O
it	O
may	O
still	O
be	O
necessary	O
to	O
use	O
the	O
slower	O
method	O
of	O
reading	O
all	O
the	O
complete	O
article	O
headers	O
.	O
</s>
<s>
Among	O
the	O
operators	O
and	O
users	O
of	O
commercial	O
news	B-Application
servers	I-Application
,	O
common	O
concerns	O
are	O
the	O
continually	O
increasing	O
storage	O
and	O
network	O
capacity	O
requirements	O
and	O
their	O
effects	O
.	O
</s>
<s>
Speed	O
,	O
in	O
relation	O
to	O
Usenet	B-Application
,	O
is	O
how	O
quickly	O
a	O
server	O
can	O
deliver	O
an	O
article	O
to	O
the	O
user	O
.	O
</s>
<s>
The	O
speed	O
of	O
data	O
traveling	O
throughout	O
the	O
farm	O
can	O
be	O
severely	O
bottlenecked	O
through	O
hard	B-Device
drive	I-Device
operations	O
.	O
</s>
<s>
Retrieving	O
the	O
article	O
and	O
overview	O
information	O
can	O
cause	O
massive	O
stress	O
on	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
To	O
combat	O
this	O
,	O
caching	B-General_Concept
technology	O
and	O
cylindrical	O
file	O
storage	O
systems	O
have	O
been	O
developed	O
.	O
</s>
<s>
Article	O
sizes	O
are	O
limited	O
to	O
what	O
each	O
news	B-Application
server	I-Application
will	O
accept	O
.	O
</s>
<s>
It	O
's	O
important	O
to	O
understand	O
that	O
retention	O
time	O
varies	O
between	O
different	O
newsgroups	B-Application
within	O
the	O
text	O
and	O
binary	O
categories	O
.	O
</s>
<s>
Omicron	O
's	O
HW	O
Media	O
is	O
currently	O
the	O
Usenet	B-Application
server	O
with	O
the	O
highest	O
amount	O
of	O
binary	O
retention	O
,	O
while	O
Google	O
is	O
the	O
Usenet	B-Application
server	O
with	O
the	O
highest	O
amount	O
of	O
text	O
retention	O
.	O
</s>
<s>
A	O
sampling	O
of	O
many	O
or	O
all	O
articles	O
,	O
preferably	O
in	O
more	O
than	O
one	O
newsgroup	B-Application
,	O
is	O
required	O
to	O
detect	O
such	O
anomalies	O
.	O
</s>
<s>
News	B-Application
servers	I-Application
do	O
not	O
have	O
unlimited	O
storage	O
,	O
and	O
due	O
to	O
this	O
fact	O
they	O
can	O
only	O
hold	O
posts	O
for	O
a	O
length	O
of	O
time	O
before	O
they	O
must	O
delete	O
them	O
in	O
order	O
to	O
make	O
room	O
for	O
new	O
posts	O
.	O
</s>
<s>
This	O
is	O
a	O
particular	O
problem	O
to	O
binary	O
newsgroups	B-Application
which	O
transmit	O
large	O
volumes	O
of	O
articles	O
.	O
</s>
<s>
For	O
news	B-Application
servers	I-Application
provided	O
by	O
Internet	O
Service	O
Providers	O
as	O
part	O
of	O
a	O
user	O
's	O
subscription	O
package	O
,	O
typical	O
retention	O
rates	O
are	O
usually	O
only	O
2	O
–	O
4	O
days	O
.	O
</s>
<s>
To	O
deal	O
with	O
the	O
increase	O
of	O
Usenet	B-Application
traffic	O
,	O
many	O
providers	O
turn	O
to	O
a	O
hybrid	O
system	O
,	O
in	O
which	O
old	O
articles	O
not	O
found	O
on	O
the	O
provider	O
's	O
server	O
will	O
request	O
the	O
article	O
from	O
another	O
server	O
with	O
longer	O
retention	O
.	O
</s>
<s>
Practical	O
limitations	O
to	O
this	O
type	O
of	O
measurement	O
include	O
the	O
impossibility	O
of	O
obtaining	O
lists	O
from	O
all	O
servers	O
worldwide	O
,	O
the	O
fact	O
that	O
many	O
servers	O
filter	O
out	O
spam	O
or	O
employ	O
Usenet	B-Architecture
Death	I-Architecture
Penalties	I-Architecture
,	O
and	O
that	O
some	O
servers	O
mask	O
incompletion	O
by	O
hiding	O
multipart	O
binary	O
sets	O
with	O
missing	O
articles	O
.	O
</s>
<s>
All	O
Usenet	B-Application
servers	O
peer	O
with	O
one	O
or	O
more	O
other	O
servers	O
in	O
order	O
to	O
exchange	O
articles	O
.	O
</s>
<s>
Although	O
there	O
are	O
several	O
web	O
resources	O
which	O
may	O
aid	O
in	O
finding	O
peers	O
,	O
a	O
better	O
resource	O
is	O
the	O
newsgroup	B-Application
(	O
Google	O
Groups	O
portal	O
)	O
.	O
</s>
<s>
Due	O
to	O
the	O
large	O
amount	O
of	O
data	O
in	O
a	O
full	O
binary+text	O
Usenet	B-Application
feed	O
(	O
can	O
be	O
high	O
as	O
30	O
terabytes	O
a	O
day	O
)	O
and	O
the	O
high	O
costs	O
of	O
transmitting	O
that	O
data	O
through	O
an	O
IP	O
transit	O
provider	O
like	O
Cogent	O
,	O
Telia	O
,	O
or	O
Zayo	O
,	O
most	O
Usenet	B-Application
providers	O
will	O
only	O
engage	O
in	O
binary	O
peering	O
when	O
they	O
are	O
interconnected	O
at	O
an	O
Internet	O
exchange	O
like	O
AMS-IX	O
,	O
SIX	O
,	O
or	O
DeCIX	O
.	O
</s>
<s>
When	O
the	O
server	O
stores	O
the	O
body	O
of	O
an	O
article	O
,	O
it	O
places	O
it	O
in	O
a	O
disk	B-Device
storage	O
area	O
generically	O
called	O
a	O
"	O
spool	O
"	O
.	O
</s>
<s>
Its	O
performance	O
capability	O
is	O
a	O
direct	O
function	O
of	O
the	O
underlying	O
operating	B-General_Concept
system	I-General_Concept
's	O
ability	O
to	O
create	O
,	O
remove	O
and	O
locate	O
files	O
within	O
a	O
directory	B-Application
,	O
and	O
often	O
this	O
scheme	O
is	O
insufficient	O
to	O
keep	O
up	O
with	O
modern	O
Usenet	B-Application
traffic	O
.	O
</s>
<s>
Nearly	O
all	O
current	O
software	O
using	O
this	O
scheme	O
stores	O
articles	O
using	O
the	O
B	B-Application
News	I-Application
2.10	O
layout	O
.	O
</s>
<s>
The	O
major	O
advantages	O
of	O
this	O
system	O
include	O
predictable	O
storage	O
requirements	O
if	O
an	O
overwriting	O
scheme	O
is	O
employed	O
,	O
and	O
some	O
freedom	O
from	O
dependency	O
on	O
the	O
underlying	O
performance	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
There	O
is	O
,	O
however	O
,	O
less	O
flexibility	O
to	O
retain	O
articles	O
by	O
age	O
rather	O
than	O
space	O
used	O
,	O
and	O
traditional	O
text	O
manipulation	O
tools	O
such	O
as	O
grep	B-Application
are	O
less	O
well	O
suited	O
to	O
analyzing	O
these	O
files	O
.	O
</s>
<s>
Some	O
degree	O
of	O
article	O
longevity	O
control	O
can	O
be	O
exercised	O
by	O
directing	O
subsets	O
of	O
the	O
newsgroups	B-Application
to	O
specific	O
sets	O
of	O
container	O
files	O
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
a	O
relational	B-Application
database	I-Application
or	O
similar	O
is	O
used	O
to	O
contain	O
the	O
spool	O
.	O
</s>
<s>
This	O
is	O
most	O
commonly	O
seen	O
with	O
Internet	B-Application
forum	I-Application
software	I-Application
that	O
also	O
offers	O
an	O
NNTP	B-Protocol
interface	O
.	O
</s>
<s>
Some	O
servers	O
,	O
such	O
as	O
INN	B-Application
,	O
allow	O
multiple	O
storage	O
schemes	O
to	O
be	O
used	O
at	O
once	O
.	O
</s>
<s>
Various	O
hybrid	O
storage	O
schemes	O
have	O
also	O
been	O
used	O
in	O
news	B-Application
servers	I-Application
,	O
including	O
different	O
organizations	O
of	O
the	O
file-per-article	O
method	O
,	O
or	O
smaller	O
containers	O
carrying	O
perhaps	O
100	O
articles	O
apiece	O
.	O
</s>
<s>
A	O
reader	O
server	O
provides	O
an	O
interface	O
to	O
read	O
and	O
post	O
articles	O
,	O
generally	O
with	O
the	O
assistance	O
of	O
a	O
news	B-Protocol
client	I-Protocol
.	O
</s>
<s>
Modern	O
transit	O
servers	O
usually	O
use	O
NNTP	B-Protocol
to	O
exchange	O
news	O
continually	O
over	O
the	O
Internet	O
and	O
similar	O
always-on	O
connections	O
.	O
</s>
<s>
In	O
the	O
past	O
,	O
servers	O
normally	O
employed	O
the	O
UUCP	B-Protocol
protocol	O
,	O
which	O
was	O
designed	O
for	O
intermittent	O
dial-up	O
connections	O
.	O
</s>
<s>
News	B-Application
servers	I-Application
normally	O
connect	O
with	O
multiple	O
peers	O
,	O
with	O
the	O
redundancy	O
helping	O
to	O
spread	O
loads	O
and	O
ensure	O
that	O
articles	O
are	O
not	O
lost	O
.	O
</s>
<s>
Distribution	O
-	O
(	O
optional	O
)	O
a	O
supplement	O
to	O
Newsgroups	B-Application
,	O
used	O
to	O
restrict	O
circulation	O
of	O
articles	O
.	O
</s>
<s>
It	O
compares	O
the	O
Newsgroups	B-Application
and	O
Distribution	O
of	O
each	O
newly	O
arrived	O
article	O
against	O
a	O
set	O
of	O
patterns	O
called	O
newsfeeds	O
,	O
listing	O
each	O
remote	O
server	O
and	O
the	O
newsgroups	B-Application
its	O
operator	O
wishes	O
to	O
receive	O
.	O
</s>
<s>
A	O
message	O
is	O
normally	O
discarded	O
if	O
the	O
Message-ID	O
is	O
duplicated	O
by	O
an	O
article	O
already	O
received	O
(	O
i.e.	O
,	O
another	O
server	O
sent	O
it	O
in	O
the	O
meantime	O
)	O
,	O
the	O
Date	O
or	O
Expires	O
lines	O
indicate	O
that	O
the	O
article	O
is	O
too	O
old	O
,	O
the	O
header	O
syntax	O
appears	O
to	O
be	O
invalid	O
,	O
the	O
Approved	O
header	O
is	O
missing	O
for	O
a	O
moderated	O
newsgroup	B-Application
,	O
or	O
additional	O
local	O
rules	O
disallow	O
it	O
.	O
</s>
<s>
Most	O
servers	O
also	O
maintain	O
a	O
list	O
of	O
active	O
newsgroups	B-Application
.	O
</s>
<s>
If	O
the	O
Newsgroups	B-Application
header	O
of	O
a	O
new	O
article	O
does	O
not	O
match	O
the	O
active	O
list	O
,	O
it	O
may	O
be	O
discarded	O
or	O
placed	O
in	O
a	O
special	O
"	O
junk	O
"	O
newsgroup	B-Application
.	O
</s>
<s>
They	O
are	O
typically	O
filed	O
in	O
special	O
"	O
control	O
"	O
newsgroups	B-Application
and	O
may	O
cause	O
the	O
server	O
to	O
automatically	O
carry	O
out	O
exceptional	O
actions	O
.	O
</s>
<s>
The	O
newgroup	B-Protocol
and	O
rmgroup	O
commands	O
can	O
cause	O
newsgroups	B-Application
to	O
be	O
created	O
or	O
removed	O
;	O
checkgroups	O
can	O
be	O
used	O
to	O
reconcile	O
the	O
local	O
active	O
list	O
with	O
a	O
commonly	O
accepted	O
set	O
;	O
and	O
cancel	O
commands	O
are	O
used	O
to	O
request	O
the	O
deletion	O
of	O
a	O
specific	O
article	O
.	O
</s>
<s>
ihave	O
and	O
sendme	O
are	O
sometimes	O
used	O
with	O
UUCP	B-Protocol
to	O
transmit	O
lists	O
of	O
offered	O
and	O
wanted	O
Message-IDs	O
.	O
</s>
<s>
A	O
reader	O
server	O
is	O
one	O
that	O
makes	O
the	O
articles	O
available	O
in	O
the	O
hierarchical	O
disk	B-Device
directory	B-Application
format	O
originated	O
by	O
B	B-Application
News	I-Application
2.10	O
,	O
or	O
offers	O
the	O
NNTP	B-Protocol
or	O
IMAP	B-Protocol
commands	O
,	O
for	O
use	O
by	O
newsreaders	B-Protocol
.	O
</s>
<s>
A	O
reader	O
server	O
typically	O
also	O
works	O
as	O
a	O
transit	O
server	O
,	O
but	O
it	O
may	O
operate	O
independently	O
or	O
serve	O
as	O
an	O
alternative	O
interface	O
to	O
an	O
Internet	B-Application
forum	I-Application
.	O
</s>
<s>
When	O
receiving	O
news	O
,	O
this	O
type	O
of	O
server	O
must	O
perform	O
the	O
additional	O
steps	O
of	O
filing	O
articles	O
into	O
newsgroups	B-Application
and	O
assigning	O
sequential	O
numbers	O
within	O
each	O
group	O
.	O
</s>
<s>
Reader	O
servers	O
typically	O
also	O
maintain	O
a	O
News	B-Application
Overview	I-Application
(	O
NOV	B-Application
)	O
database	O
that	O
allows	O
newsreaders	B-Protocol
to	O
quickly	O
obtain	O
message	O
summaries	O
and	O
present	O
messages	O
in	O
threaded	O
form	O
.	O
</s>
<s>
Most	O
reader	O
servers	O
support	O
posting	O
,	O
either	O
through	O
NNTP	B-Protocol
or	O
a	O
special	O
inews	O
program	O
.	O
</s>
<s>
If	O
the	O
article	O
is	O
posted	O
to	O
a	O
moderated	O
group	O
,	O
the	O
server	O
will	O
attempt	O
to	O
mail	O
it	O
to	O
the	O
newsgroup	B-Application
moderator	O
if	O
the	O
Approved	O
header	O
is	O
absent	O
.	O
</s>
<s>
Smaller	O
sites	O
with	O
limited	O
network	O
bandwidth	O
may	O
operate	O
"	O
sucking	O
"	O
or	O
cache	B-General_Concept
servers	O
.	O
</s>
<s>
These	O
perform	O
the	O
same	O
reader	O
server	O
role	O
as	O
conventional	O
news	B-Application
servers	I-Application
,	O
but	O
themselves	O
act	O
as	O
newsreaders	B-Protocol
to	O
exchange	O
articles	O
with	O
other	O
reader	O
servers	O
.	O
</s>
