<s>
A	O
network	B-Protocol
switch	I-Protocol
(	O
also	O
called	O
switching	B-Protocol
hub	I-Protocol
,	O
bridging	B-Protocol
hub	I-Protocol
,	O
and	O
,	O
by	O
the	O
IEEE	O
,	O
MAC	B-Protocol
bridge	I-Protocol
)	O
is	O
networking	B-Device
hardware	I-Device
that	O
connects	O
devices	O
on	O
a	O
computer	B-Architecture
network	I-Architecture
by	O
using	O
packet	B-Protocol
switching	I-Protocol
to	O
receive	O
and	O
forward	O
data	O
to	O
the	O
destination	O
device	O
.	O
</s>
<s>
A	O
network	B-Protocol
switch	I-Protocol
is	O
a	O
multiport	O
network	B-Protocol
bridge	I-Protocol
that	O
uses	O
MAC	O
addresses	O
to	O
forward	O
data	O
at	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
layer	B-Protocol
2	I-Protocol
)	O
of	O
the	O
OSI	O
model	O
.	O
</s>
<s>
Some	O
switches	O
can	O
also	O
forward	O
data	O
at	O
the	O
network	B-Application
layer	I-Application
(	O
layer	B-Application
3	I-Application
)	O
by	O
additionally	O
incorporating	O
routing	B-Protocol
functionality	O
.	O
</s>
<s>
Such	O
switches	O
are	O
commonly	O
known	O
as	O
layer-3	B-Application
switches	I-Application
or	O
multilayer	B-Application
switches	I-Application
.	O
</s>
<s>
Switches	O
for	O
Ethernet	O
are	O
the	O
most	O
common	O
form	O
of	O
network	B-Protocol
switch	I-Protocol
.	O
</s>
<s>
The	O
first	O
MAC	B-Protocol
Bridge	I-Protocol
was	O
invented	O
in	O
1983	O
by	O
Mark	O
Kempf	O
,	O
an	O
engineer	O
in	O
the	O
Networking	O
Advanced	O
Development	O
group	O
of	O
Digital	O
Equipment	O
Corporation	O
.	O
</s>
<s>
The	O
company	O
subsequently	O
produced	O
multi-port	O
switches	O
for	O
both	O
Ethernet	O
and	O
FDDI	B-Protocol
such	O
as	O
GigaSwitch	O
.	O
</s>
<s>
Digital	O
decided	O
to	O
license	O
its	O
MAC	B-Protocol
Bridge	I-Protocol
patent	O
in	O
a	O
royalty-free	O
,	O
non-discriminatory	O
basis	O
that	O
allowed	O
IEEE	O
standardization	O
.	O
</s>
<s>
Ethernet	O
was	O
initially	O
a	O
shared-access	B-Protocol
medium	I-Protocol
,	O
but	O
the	O
introduction	O
of	O
the	O
MAC	B-Protocol
bridge	I-Protocol
began	O
its	O
transformation	O
into	O
its	O
most-common	O
point-to-point	O
form	O
without	O
a	O
collision	B-Protocol
domain	I-Protocol
.	O
</s>
<s>
Switches	O
also	O
exist	O
for	O
other	O
types	O
of	O
networks	O
including	O
Fibre	B-Architecture
Channel	I-Architecture
,	O
Asynchronous	O
Transfer	O
Mode	O
,	O
and	O
InfiniBand	B-Architecture
.	O
</s>
<s>
Unlike	O
repeater	B-Protocol
hubs	I-Protocol
,	O
which	O
broadcast	B-Operating_System
the	O
same	O
data	O
out	O
of	O
each	O
port	O
and	O
let	O
the	O
devices	O
pick	O
out	O
the	O
data	O
addressed	O
to	O
them	O
,	O
a	O
network	B-Protocol
switch	I-Protocol
learns	O
the	O
identities	O
of	O
connected	O
devices	O
and	O
then	O
only	O
forwards	O
data	O
to	O
the	O
port	O
connected	O
to	O
the	O
device	O
to	O
which	O
it	O
is	O
addressed	O
.	O
</s>
<s>
A	O
switch	O
is	O
a	O
device	O
in	O
a	O
computer	B-Architecture
network	I-Architecture
that	O
connects	O
other	O
devices	O
together	O
.	O
</s>
<s>
Switches	O
manage	O
the	O
flow	O
of	O
data	O
across	O
a	O
network	O
by	O
transmitting	O
a	O
received	O
network	B-Protocol
packet	I-Protocol
only	O
to	O
the	O
one	O
or	O
more	O
devices	O
for	O
which	O
the	O
packet	B-Protocol
is	O
intended	O
.	O
</s>
<s>
Each	O
networked	O
device	O
connected	O
to	O
a	O
switch	O
can	O
be	O
identified	O
by	O
its	O
network	B-Protocol
address	I-Protocol
,	O
allowing	O
the	O
switch	O
to	O
direct	O
the	O
flow	O
of	O
traffic	O
maximizing	O
the	O
security	O
and	O
efficiency	O
of	O
the	O
network	O
.	O
</s>
<s>
A	O
switch	O
is	O
more	O
intelligent	O
than	O
an	O
Ethernet	B-Protocol
hub	I-Protocol
,	O
which	O
simply	O
retransmits	O
packets	B-Protocol
out	O
of	O
every	O
port	O
of	O
the	O
hub	B-Protocol
except	O
the	O
port	O
on	O
which	O
the	O
packet	B-Protocol
was	O
received	O
,	O
unable	O
to	O
distinguish	O
different	O
recipients	O
,	O
and	O
achieving	O
an	O
overall	O
lower	O
network	O
efficiency	O
.	O
</s>
<s>
An	O
Ethernet	B-Protocol
switch	I-Protocol
operates	O
at	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
layer2	O
)	O
of	O
the	O
OSI	O
model	O
to	O
create	O
a	O
separate	O
collision	B-Protocol
domain	I-Protocol
for	O
each	O
switch	B-Protocol
port	I-Protocol
.	O
</s>
<s>
Each	O
device	O
connected	O
to	O
a	O
switch	B-Protocol
port	I-Protocol
can	O
transfer	O
data	O
to	O
any	O
of	O
the	O
other	O
ports	O
at	O
any	O
time	O
and	O
the	O
transmissions	O
will	O
not	O
interfere	O
.	O
</s>
<s>
Because	O
broadcasts	B-Operating_System
are	O
still	O
being	O
forwarded	O
to	O
all	O
connected	O
devices	O
by	O
the	O
switch	O
,	O
the	O
newly	O
formed	O
network	B-Protocol
segment	I-Protocol
continues	O
to	O
be	O
a	O
broadcast	B-Architecture
domain	I-Architecture
.	O
</s>
<s>
Switches	O
may	O
also	O
operate	O
at	O
higher	O
layers	O
of	O
the	O
OSI	O
model	O
,	O
including	O
the	O
network	B-Application
layer	I-Application
and	O
above	O
.	O
</s>
<s>
A	O
switch	O
that	O
also	O
operates	O
at	O
these	O
higher	O
layers	O
is	O
known	O
as	O
a	O
multilayer	B-Application
switch	I-Application
.	O
</s>
<s>
Segmentation	O
involves	O
the	O
use	O
of	O
a	O
switch	O
to	O
split	O
a	O
larger	O
collision	B-Protocol
domain	I-Protocol
into	O
smaller	O
ones	O
in	O
order	O
to	O
reduce	O
collision	O
probability	O
and	O
to	O
improve	O
overall	O
network	O
throughput	O
.	O
</s>
<s>
micro-segmentation	O
)	O
,	O
each	O
device	O
is	O
located	O
on	O
a	O
dedicated	O
switch	B-Protocol
port	I-Protocol
.	O
</s>
<s>
In	O
contrast	O
to	O
an	O
Ethernet	B-Protocol
hub	I-Protocol
,	O
there	O
is	O
a	O
separate	O
collision	B-Protocol
domain	I-Protocol
on	O
each	O
of	O
the	O
switch	B-Protocol
ports	I-Protocol
.	O
</s>
<s>
Full-duplex	O
mode	O
has	O
only	O
one	O
transmitter	O
and	O
one	O
receiver	O
per	O
collision	B-Protocol
domain	I-Protocol
,	O
making	O
collisions	O
impossible	O
.	O
</s>
<s>
The	O
network	B-Protocol
switch	I-Protocol
plays	O
an	O
integral	O
role	O
in	O
most	O
modern	O
Ethernet	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
(	O
LANs	B-General_Concept
)	O
.	O
</s>
<s>
Mid-to-large	O
sized	O
LANs	B-General_Concept
contain	O
a	O
number	O
of	O
linked	O
managed	B-Protocol
switches	I-Protocol
.	O
</s>
<s>
Small	O
office/home	O
office	O
(	O
SOHO	O
)	O
applications	O
typically	O
use	O
a	O
single	O
switch	O
,	O
or	O
an	O
all-purpose	O
device	O
such	O
as	O
a	O
residential	B-Application
gateway	I-Application
to	O
access	O
small	O
office/home	O
broadband	B-General_Concept
services	O
such	O
as	O
DSL	O
or	O
cable	B-Device
Internet	I-Device
.	O
</s>
<s>
In	O
most	O
of	O
these	O
cases	O
,	O
the	O
end-user	O
device	O
contains	O
a	O
router	B-Protocol
and	O
components	O
that	O
interface	O
to	O
the	O
particular	O
physical	O
broadband	B-General_Concept
technology	O
.	O
</s>
<s>
In	O
the	O
hierarchical	B-Protocol
internetworking	I-Protocol
model	I-Protocol
and	O
similar	O
network	O
architectures	O
,	O
switches	O
are	O
also	O
used	O
deeper	O
in	O
the	O
network	O
to	O
provide	O
connections	O
between	O
the	O
switches	O
at	O
the	O
edge	O
.	O
</s>
<s>
In	O
switches	O
intended	O
for	O
commercial	O
use	O
,	O
built-in	O
or	O
modular	O
interfaces	O
make	O
it	O
possible	O
to	O
connect	O
different	O
types	O
of	O
networks	O
,	O
including	O
Ethernet	O
,	O
Fibre	B-Architecture
Channel	I-Architecture
,	O
RapidIO	B-General_Concept
,	O
ATM	O
,	O
ITU-T	B-General_Concept
G.hn	I-General_Concept
and	O
802.11	O
.	O
</s>
<s>
While	O
the	O
layer-2	B-Protocol
functionality	O
is	O
adequate	O
for	O
bandwidth-shifting	O
within	O
one	O
technology	O
,	O
interconnecting	O
technologies	O
such	O
as	O
Ethernet	O
and	O
Token	B-Device
Ring	I-Device
is	O
performed	O
more	O
easily	O
at	O
layer	B-Application
3	I-Application
or	O
via	O
routing	B-Protocol
.	O
</s>
<s>
Devices	O
that	O
interconnect	O
at	O
the	O
layer3	O
are	O
traditionally	O
called	O
routers	B-Protocol
.	O
</s>
<s>
Where	O
there	O
is	O
a	O
need	O
for	O
a	O
great	O
deal	O
of	O
analysis	O
of	O
network	O
performance	O
and	O
security	O
,	O
switches	O
may	O
be	O
connected	O
between	O
WAN	O
routers	B-Protocol
as	O
places	O
for	O
analytic	O
modules	O
.	O
</s>
<s>
Some	O
vendors	O
provide	O
firewall	B-Application
,	O
network	O
intrusion	O
detection	O
,	O
and	O
performance	O
analysis	O
modules	O
that	O
can	O
plug	O
into	O
switch	B-Protocol
ports	I-Protocol
.	O
</s>
<s>
Through	O
port	B-Protocol
mirroring	I-Protocol
,	O
a	O
switch	O
can	O
create	O
a	O
mirror	O
image	O
of	O
data	O
that	O
can	O
go	O
to	O
an	O
external	O
device	O
such	O
as	O
intrusion	O
detection	O
systems	O
and	O
packet	B-Protocol
sniffers	I-Protocol
.	O
</s>
<s>
A	O
modern	O
switch	O
may	O
implement	O
power	B-Device
over	I-Device
Ethernet	I-Device
(	O
PoE	B-Device
)	O
,	O
which	O
avoids	O
the	O
need	O
for	O
attached	O
devices	O
,	O
such	O
as	O
a	O
VoIP	B-Device
phone	I-Device
or	O
wireless	B-Device
access	I-Device
point	I-Device
,	O
to	O
have	O
a	O
separate	O
power	O
supply	O
.	O
</s>
<s>
The	O
core	O
function	O
of	O
an	O
Ethernet	B-Protocol
switch	I-Protocol
is	O
to	O
provide	O
multiple	O
ports	O
of	O
layer-2	B-Protocol
bridging	B-Protocol
.	O
</s>
<s>
A	O
device	O
capable	O
of	O
more	O
than	O
bridging	B-Protocol
is	O
known	O
as	O
a	O
multilayer	B-Application
switch	I-Application
.	O
</s>
<s>
A	O
layer	B-Protocol
2	I-Protocol
network	B-Device
device	I-Device
is	O
a	O
multiport	O
device	O
that	O
uses	O
hardware	O
addresses	O
(	O
MAC	O
addresses	O
)	O
to	O
process	O
and	O
forward	O
data	O
at	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
layer	B-Protocol
2	I-Protocol
)	O
.	O
</s>
<s>
A	O
switch	O
operating	O
as	O
a	O
network	B-Protocol
bridge	I-Protocol
may	O
interconnect	O
otherwise	O
separate	O
layer	B-Protocol
2	I-Protocol
networks	O
.	O
</s>
<s>
Bridges	O
also	O
buffer	O
an	O
incoming	O
packet	B-Protocol
and	O
adapt	O
the	O
transmission	O
speed	O
to	O
that	O
of	O
the	O
outgoing	O
port	O
.	O
</s>
<s>
While	O
there	O
are	O
specialized	O
applications	O
,	O
such	O
as	O
storage	O
area	O
networks	O
,	O
where	O
the	O
input	O
and	O
output	O
interfaces	O
are	O
the	O
same	O
bandwidth	O
,	O
this	O
is	O
not	O
always	O
the	O
case	O
in	O
general	O
LAN	B-General_Concept
applications	I-General_Concept
.	O
</s>
<s>
In	O
LANs	B-General_Concept
,	O
a	O
switch	O
used	O
for	O
end-user	O
access	O
typically	O
concentrates	O
lower	O
bandwidth	O
and	O
uplinks	B-Application
into	O
a	O
higher	O
bandwidth	O
.	O
</s>
<s>
Interconnects	O
between	O
switches	O
may	O
be	O
regulated	O
using	O
the	O
spanning	B-Protocol
tree	I-Protocol
protocol	I-Protocol
(	O
STP	O
)	O
that	O
disables	O
forwarding	O
on	O
links	O
so	O
that	O
the	O
resulting	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
is	O
a	O
tree	O
without	O
switching	B-Architecture
loops	I-Architecture
.	O
</s>
<s>
In	O
contrast	O
to	O
routers	B-Protocol
,	O
spanning	O
tree	O
bridges	O
must	O
have	O
topologies	O
with	O
only	O
one	O
active	O
path	O
between	O
two	O
points	O
.	O
</s>
<s>
Shortest	B-Protocol
path	I-Protocol
bridging	I-Protocol
and	O
TRILL	B-Protocol
(	O
TRansparent	B-Protocol
Interconnection	I-Protocol
of	I-Protocol
Lots	I-Protocol
of	I-Protocol
Links	I-Protocol
)	O
are	O
layer	B-Protocol
2	I-Protocol
alternatives	O
to	O
STP	O
which	O
allow	O
all	O
paths	O
to	O
be	O
active	O
with	O
multiple	O
equal	O
cost	O
paths	O
.	O
</s>
<s>
Switches	O
are	O
available	O
in	O
many	O
form	O
factors	O
,	O
including	O
stand-alone	O
,	O
desktop	O
units	O
which	O
are	O
typically	O
intended	O
to	O
be	O
used	O
in	O
a	O
home	O
or	O
office	O
environment	O
outside	O
a	O
wiring	O
closet	O
;	O
rack-mounted	B-Application
switches	O
for	O
use	O
in	O
an	O
equipment	B-Application
rack	I-Application
or	O
an	O
enclosure	O
;	O
DIN	O
rail	O
mounted	O
for	O
use	O
in	O
industrial	B-Protocol
environments	I-Protocol
;	O
and	O
small	O
installation	O
switches	O
,	O
mounted	O
into	O
a	O
cable	O
duct	O
,	O
floor	O
box	O
or	O
communications	O
tower	O
,	O
as	O
found	O
,	O
for	O
example	O
,	O
in	O
fiber	B-Architecture
to	I-Architecture
the	I-Architecture
office	I-Architecture
infrastructures	O
.	O
</s>
<s>
Rack-mounted	B-Application
switches	O
may	O
be	O
standalone	O
units	O
,	O
stackable	B-Protocol
switches	I-Protocol
or	O
large	O
chassis	O
units	O
with	O
swappable	O
line	O
cards	O
.	O
</s>
<s>
They	O
are	O
plug	B-Device
and	I-Device
play	I-Device
.	O
</s>
<s>
Unmanaged	O
switches	O
can	O
be	O
desktop	O
or	O
rack	B-Application
mounted	I-Application
.	O
</s>
<s>
Managed	B-Protocol
switches	I-Protocol
have	O
one	O
or	O
more	O
methods	O
to	O
modify	O
the	O
operation	O
of	O
the	O
switch	O
.	O
</s>
<s>
Common	O
management	O
methods	O
include	O
:	O
a	O
command-line	B-Application
interface	I-Application
(	O
CLI	O
)	O
accessed	O
via	O
serial	B-Device
console	I-Device
,	O
telnet	B-Protocol
or	O
Secure	B-Protocol
Shell	I-Protocol
,	O
an	O
embedded	O
Simple	B-Protocol
Network	I-Protocol
Management	I-Protocol
Protocol	I-Protocol
(	O
SNMP	B-Protocol
)	O
agent	O
allowing	O
management	O
from	O
a	O
remote	O
console	O
or	O
management	O
station	O
,	O
or	O
a	O
web	O
interface	O
for	O
management	O
from	O
a	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
Two	O
sub-classes	O
of	O
managed	B-Protocol
switches	I-Protocol
are	O
smart	O
and	O
enterprise	O
managed	B-Protocol
switches	I-Protocol
.	O
</s>
<s>
Smart	O
switches	O
(	O
aka	O
intelligent	O
switches	O
)	O
are	O
managed	B-Protocol
switches	I-Protocol
with	O
a	O
limited	O
set	O
of	O
management	O
features	O
.	O
</s>
<s>
For	O
a	O
price	O
much	O
lower	O
than	O
a	O
fully	O
managed	B-Protocol
switch	I-Protocol
they	O
provide	O
a	O
web	O
interface	O
(	O
and	O
usually	O
no	O
CLI	O
access	O
)	O
and	O
allow	O
configuration	O
of	O
basic	O
settings	O
,	O
such	O
as	O
VLANs	O
,	O
port-bandwidth	O
and	O
duplex	O
.	O
</s>
<s>
Enterprise	O
managed	B-Protocol
switches	I-Protocol
(	O
aka	O
managed	B-Protocol
switches	I-Protocol
)	O
have	O
a	O
full	O
set	O
of	O
management	O
features	O
,	O
including	O
CLI	O
,	O
SNMP	B-Protocol
agent	O
,	O
and	O
web	O
interface	O
.	O
</s>
<s>
A	O
stackable	B-Protocol
switch	I-Protocol
is	O
a	O
type	O
of	O
an	O
enterprise-managed	O
switch	O
.	O
</s>
<s>
Port	B-Protocol
mirroring	I-Protocol
the	O
switch	O
sends	O
a	O
copy	O
of	O
network	B-Protocol
packets	I-Protocol
to	O
a	O
monitoring	O
network	O
connection	O
.	O
</s>
<s>
SMON	O
"	O
Switch	O
Monitoring	O
"	O
is	O
described	O
by	O
RFC	O
2613	O
and	O
is	O
a	O
protocol	O
for	O
controlling	O
facilities	O
such	O
as	O
port	B-Protocol
mirroring	I-Protocol
.	O
</s>
<s>
Other	O
monitoring	O
methods	O
include	O
connecting	O
a	O
layer-1	O
hub	B-Protocol
or	O
network	B-Device
tap	I-Device
between	O
the	O
monitored	O
device	O
and	O
its	O
switch	B-Protocol
port	I-Protocol
.	O
</s>
