<s>
A	O
packet	B-Protocol
analyzer	I-Protocol
,	O
also	O
known	O
as	O
packet	B-Protocol
sniffer	I-Protocol
,	O
protocol	B-Protocol
analyzer	I-Protocol
,	O
or	O
network	O
analyzer	O
,	O
is	O
a	O
computer	B-Application
program	I-Application
or	O
computer	B-Architecture
hardware	I-Architecture
such	O
as	O
a	O
packet	B-Protocol
capture	I-Protocol
appliance	I-Protocol
,	O
that	O
can	O
intercept	O
and	O
log	O
traffic	O
that	O
passes	O
over	O
a	O
computer	B-Architecture
network	I-Architecture
or	O
part	O
of	O
a	O
network	O
.	O
</s>
<s>
Packet	B-Protocol
capture	I-Protocol
is	O
the	O
process	O
of	O
intercepting	O
and	O
logging	O
traffic	O
.	O
</s>
<s>
As	O
data	B-General_Concept
streams	I-General_Concept
flow	O
across	O
the	O
network	O
,	O
the	O
analyzer	O
captures	O
each	O
packet	B-Protocol
and	O
,	O
if	O
needed	O
,	O
decodes	O
the	O
packet	B-Protocol
's	O
raw	O
data	O
,	O
showing	O
the	O
values	O
of	O
various	O
fields	O
in	O
the	O
packet	B-Protocol
,	O
and	O
analyzes	O
its	O
content	O
according	O
to	O
the	O
appropriate	O
RFC	O
or	O
other	O
specifications	O
.	O
</s>
<s>
A	O
packet	B-Protocol
analyzer	I-Protocol
used	O
for	O
intercepting	O
traffic	O
on	O
wireless	O
networks	O
is	O
known	O
as	O
a	O
wireless	B-Protocol
analyzer	I-Protocol
or	O
WiFi	B-Protocol
analyzer	I-Protocol
.	O
</s>
<s>
While	O
a	O
packet	B-Protocol
analyzer	I-Protocol
can	O
also	O
be	O
referred	O
to	O
as	O
a	O
network	O
analyzer	O
or	O
protocol	B-Protocol
analyzer	I-Protocol
these	O
terms	O
can	O
also	O
have	O
other	O
meanings	O
.	O
</s>
<s>
Protocol	B-Protocol
analyzer	I-Protocol
can	O
technically	O
be	O
a	O
broader	O
,	O
more	O
general	O
class	O
that	O
includes	O
packet	O
analyzers/sniffers	O
.	O
</s>
<s>
On	O
wired	O
shared-medium	B-Protocol
networks	I-Protocol
,	O
such	O
as	O
Ethernet	O
,	O
Token	B-Device
Ring	I-Device
,	O
and	O
FDDI	B-Protocol
,	O
depending	O
on	O
the	O
network	O
structure	O
(	O
hub	B-Protocol
or	O
switch	B-Protocol
)	O
,	O
it	O
may	O
be	O
possible	O
to	O
capture	O
all	O
traffic	O
on	O
the	O
network	O
from	O
a	O
single	O
machine	O
.	O
</s>
<s>
On	O
modern	O
networks	O
,	O
traffic	O
can	O
be	O
captured	O
using	O
a	O
network	B-Protocol
switch	I-Protocol
using	O
port	B-Protocol
mirroring	I-Protocol
,	O
which	O
mirrors	O
all	O
packets	B-Protocol
that	O
pass	O
through	O
designated	O
ports	O
of	O
the	O
switch	B-Protocol
to	O
another	O
port	O
,	O
if	O
the	O
switch	B-Protocol
supports	O
port	B-Protocol
mirroring	I-Protocol
.	O
</s>
<s>
A	O
network	B-Device
tap	I-Device
is	O
an	O
even	O
more	O
reliable	O
solution	O
than	O
to	O
use	O
a	O
monitoring	O
port	O
since	O
taps	O
are	O
less	O
likely	O
to	O
drop	O
packets	B-Protocol
during	O
high	O
traffic	O
load	O
.	O
</s>
<s>
On	O
wireless	B-Architecture
LANs	I-Architecture
,	O
traffic	O
can	O
be	O
captured	O
on	O
one	O
channel	O
at	O
a	O
time	O
,	O
or	O
by	O
using	O
multiple	O
adapters	O
,	O
on	O
several	O
channels	O
simultaneously	O
.	O
</s>
<s>
On	O
wired	O
broadcast	B-Operating_System
and	O
wireless	B-Architecture
LANs	I-Architecture
,	O
to	O
capture	O
unicast	B-Protocol
traffic	O
between	O
other	O
machines	O
,	O
the	O
network	B-Protocol
adapter	I-Protocol
capturing	O
the	O
traffic	O
must	O
be	O
in	O
promiscuous	B-Protocol
mode	I-Protocol
.	O
</s>
<s>
On	O
wireless	B-Architecture
LANs	I-Architecture
,	O
even	O
if	O
the	O
adapter	O
is	O
in	O
promiscuous	B-Protocol
mode	I-Protocol
,	O
packets	B-Protocol
not	O
for	O
the	O
service	B-General_Concept
set	I-General_Concept
the	O
adapter	O
is	O
configured	O
for	O
are	O
usually	O
ignored	O
.	O
</s>
<s>
To	O
see	O
those	O
packets	B-Protocol
,	O
the	O
adapter	O
must	O
be	O
in	O
monitor	B-Protocol
mode	I-Protocol
.	O
</s>
<s>
No	O
special	O
provisions	O
are	O
required	O
to	O
capture	O
multicast	O
traffic	O
to	O
a	O
multicast	O
group	O
the	O
packet	B-Protocol
analyzer	I-Protocol
is	O
already	O
monitoring	O
,	O
or	O
broadcast	B-Operating_System
traffic	I-Operating_System
.	O
</s>
<s>
When	O
traffic	O
is	O
captured	O
,	O
either	O
the	O
entire	O
contents	O
of	O
packets	B-Protocol
or	O
just	O
the	O
headers	B-General_Concept
are	O
recorded	O
.	O
</s>
<s>
Recording	O
just	O
headers	B-General_Concept
reduces	O
storage	O
requirements	O
,	O
and	O
avoids	O
some	O
privacy	O
legal	O
issues	O
,	O
yet	O
often	O
provides	O
sufficient	O
information	O
to	O
diagnose	O
problems	O
.	O
</s>
<s>
Captured	O
information	O
is	O
decoded	O
from	O
raw	O
digital	O
form	O
into	O
a	O
human-readable	B-General_Concept
format	I-General_Concept
that	O
lets	O
engineers	O
review	O
exchanged	O
information	O
.	O
</s>
<s>
Protocol	B-Protocol
analyzers	I-Protocol
vary	O
in	O
their	O
abilities	O
to	O
display	O
and	O
analyze	O
data	O
.	O
</s>
<s>
Some	O
protocol	B-Protocol
analyzers	I-Protocol
can	O
also	O
generate	O
traffic	O
.	O
</s>
<s>
Protocol	B-Protocol
analyzers	I-Protocol
can	O
also	O
be	O
hardware-based	O
,	O
either	O
in	O
probe	O
format	O
or	O
,	O
as	O
is	O
increasingly	O
common	O
,	O
combined	O
with	O
a	O
disk	O
array	O
.	O
</s>
<s>
These	O
devices	O
record	O
packets	B-Protocol
or	O
packet	B-General_Concept
headers	I-General_Concept
to	O
a	O
disk	O
array	O
.	O
</s>
<s>
Packet	B-Protocol
analyzers	I-Protocol
can	O
:	O
</s>
<s>
Packet	B-Protocol
capture	I-Protocol
can	O
be	O
used	O
to	O
fulfill	O
a	O
warrant	O
from	O
a	O
law	O
enforcement	O
agency	O
to	O
wiretap	O
all	O
network	O
traffic	O
generated	O
by	O
an	O
individual	O
.	O
</s>
<s>
Internet	O
service	O
providers	O
and	O
VoIP	B-Application
providers	O
in	O
the	O
United	O
States	O
must	O
comply	O
with	O
Communications	O
Assistance	O
for	O
Law	O
Enforcement	O
Act	O
regulations	O
.	O
</s>
<s>
Using	O
packet	B-Protocol
capture	I-Protocol
and	O
storage	O
,	O
telecommunications	O
carriers	O
can	O
provide	O
the	O
legally	O
required	O
secure	O
and	O
separate	O
access	O
to	O
targeted	O
network	O
traffic	O
and	O
can	O
use	O
the	O
same	O
device	O
for	O
internal	O
security	O
purposes	O
.	O
</s>
