<s>
In	O
computer	B-Architecture
networking	I-Architecture
,	O
Fast	B-Protocol
Ethernet	I-Protocol
physical	B-Protocol
layers	I-Protocol
carry	O
traffic	O
at	O
the	O
nominal	O
rate	O
of	O
100Mbit/s	O
.	O
</s>
<s>
Of	O
the	O
Fast	B-Protocol
Ethernet	I-Protocol
physical	B-Protocol
layers	I-Protocol
,	O
100BASE-TX	B-Protocol
is	O
by	O
far	O
the	O
most	O
common	O
.	O
</s>
<s>
Fast	B-Protocol
Ethernet	I-Protocol
was	O
introduced	O
in	O
1995	O
as	O
the	O
IEEE	B-Protocol
802.3u	I-Protocol
standard	O
and	O
remained	O
the	O
fastest	O
version	O
of	O
Ethernet	O
for	O
three	O
years	O
before	O
the	O
introduction	O
of	O
Gigabit	O
Ethernet	O
.	O
</s>
<s>
The	O
"	O
100	O
"	O
in	O
the	O
media	O
type	O
designation	O
refers	O
to	O
the	O
transmission	O
speed	O
of	O
100Mbit/s	O
,	O
while	O
the	O
"	O
BASE	O
"	O
refers	O
to	O
baseband	B-Algorithm
signaling	I-Algorithm
.	O
</s>
<s>
refers	O
to	O
the	O
line	B-Protocol
code	I-Protocol
method	O
used	O
.	O
</s>
<s>
Fast	B-Protocol
Ethernet	I-Protocol
is	O
sometimes	O
referred	O
to	O
as	O
100BASE-X	B-Protocol
,	O
where	O
"	O
X	O
"	O
is	O
a	O
placeholder	O
for	O
the	O
FX	O
and	O
TX	O
variants	O
.	O
</s>
<s>
Fast	B-Protocol
Ethernet	I-Protocol
is	O
an	O
extension	O
of	O
the	O
10-megabit	O
Ethernet	O
standard	O
.	O
</s>
<s>
It	O
runs	O
on	O
twisted	O
pair	O
or	O
optical	B-Architecture
fiber	I-Architecture
cable	O
in	O
a	O
star	B-Architecture
wired	I-Architecture
bus	I-Architecture
topology	I-Architecture
,	O
similar	O
to	O
the	O
IEEE	O
standard	O
802.3i	B-Protocol
called	O
10BASE-T	B-Protocol
,	O
itself	O
an	O
evolution	O
of	O
10BASE5	O
(	O
802.3	O
)	O
and	O
10BASE2	O
(	O
802.3a	O
)	O
.	O
</s>
<s>
Fast	B-Protocol
Ethernet	I-Protocol
devices	O
are	O
generally	O
backward	O
compatible	O
with	O
existing	O
10BASE-T	B-Protocol
systems	O
,	O
enabling	O
plug-and-play	O
upgrades	O
from	O
10BASE-T	B-Protocol
.	O
</s>
<s>
Most	O
switches	O
and	O
other	O
networking	O
devices	O
with	O
ports	O
capable	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
can	O
perform	O
autonegotiation	B-Protocol
,	O
sensing	O
a	O
piece	O
of	O
10BASE-T	B-Protocol
equipment	O
and	O
setting	O
the	O
port	O
to	O
10BASE-T	B-Protocol
half	O
duplex	O
if	O
the	O
10BASE-T	B-Protocol
equipment	O
cannot	O
perform	O
auto	B-Protocol
negotiation	I-Protocol
itself	O
.	O
</s>
<s>
The	O
standard	O
specifies	O
the	O
use	O
of	O
CSMA/CD	O
for	O
media	B-Protocol
access	I-Protocol
control	I-Protocol
.	O
</s>
<s>
A	O
full-duplex	O
mode	O
is	O
also	O
specified	O
and	O
in	O
practice	O
,	O
all	O
modern	O
networks	O
use	O
Ethernet	B-Protocol
switches	I-Protocol
and	O
operate	O
in	O
full-duplex	O
mode	O
,	O
even	O
as	O
legacy	O
devices	O
that	O
use	O
half	O
duplex	O
still	O
exist	O
.	O
</s>
<s>
A	O
Fast	B-Protocol
Ethernet	I-Protocol
adapter	O
can	O
be	O
logically	O
divided	O
into	O
a	O
media	B-Protocol
access	I-Protocol
controller	I-Protocol
(	O
MAC	O
)	O
,	O
which	O
deals	O
with	O
the	O
higher-level	O
issues	O
of	O
medium	O
availability	O
,	O
and	O
a	O
physical	O
layer	O
interface	O
(	O
PHY	O
)	O
.	O
</s>
<s>
The	O
MAC	O
is	O
typically	O
linked	O
to	O
the	O
PHY	O
by	O
a	O
four-bit	O
25MHz	O
synchronous	O
parallel	O
interface	O
known	O
as	O
a	O
media-independent	B-Protocol
interface	I-Protocol
(	O
MII	O
)	O
,	O
or	O
by	O
a	O
two-bit	O
50MHz	O
variant	O
called	O
reduced	O
media	B-Protocol
independent	I-Protocol
interface	I-Protocol
(	O
RMII	O
)	O
.	O
</s>
<s>
In	O
rare	O
cases	O
,	O
the	O
MII	O
may	O
be	O
an	O
external	O
connection	O
but	O
is	O
usually	O
a	O
connection	O
between	O
ICs	O
in	O
a	O
network	B-Protocol
adapter	I-Protocol
or	O
even	O
two	O
sections	O
within	O
a	O
single	O
IC	O
.	O
</s>
<s>
Fast	B-Protocol
Ethernet	I-Protocol
or	O
Ethernet	B-Protocol
hubs	I-Protocol
may	O
use	O
the	O
MII	O
to	O
connect	O
to	O
multiple	O
PHYs	O
for	O
their	O
different	O
interfaces	O
.	O
</s>
<s>
The	O
MII	O
fixes	O
the	O
theoretical	O
maximum	O
data	O
bit	O
rate	O
for	O
all	O
versions	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
to	O
100Mbit/s	O
.	O
</s>
<s>
The	O
information	O
rate	O
actually	O
observed	O
on	O
real	O
networks	O
is	O
less	O
than	O
the	O
theoretical	O
maximum	O
,	O
due	O
to	O
the	O
necessary	O
header	O
and	O
trailer	O
(	O
addressing	O
and	O
error-detection	O
bits	O
)	O
on	O
every	O
Ethernet	B-Protocol
frame	I-Protocol
,	O
and	O
the	O
required	O
interpacket	B-Protocol
gap	I-Protocol
between	O
transmissions	O
.	O
</s>
<s>
100BASE-T	O
is	O
any	O
of	O
several	O
Fast	B-Protocol
Ethernet	I-Protocol
standards	O
for	O
twisted	O
pair	O
cables	O
,	O
including	O
:	O
100BASE-TX	B-Protocol
(	O
100Mbit/s	O
over	O
two-pair	O
Cat5	B-Protocol
or	O
better	O
cable	O
)	O
,	O
100BASE-T4	O
(	O
100Mbit/s	O
over	O
four-pair	O
Cat3	B-Protocol
or	O
better	O
cable	O
,	O
defunct	O
)	O
,	O
100BASE-T2	O
(	O
100Mbit/s	O
over	O
two-pair	O
Cat3	B-Protocol
or	O
better	O
cable	O
,	O
also	O
defunct	O
)	O
.	O
</s>
<s>
The	O
segment	O
length	O
for	O
a	O
100BASE-T	O
cable	O
is	O
limited	O
to	O
(	O
the	O
same	O
limit	O
as	O
10BASE-T	B-Protocol
and	O
gigabit	O
Ethernet	O
)	O
.	O
</s>
<s>
Almost	O
all	O
100BASE-T	O
installations	O
are	O
100BASE-TX	B-Protocol
.	O
</s>
<s>
100BASE-TX	B-Protocol
is	O
the	O
predominant	O
form	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
,	O
and	O
runs	O
over	O
two	O
wire-pairs	O
inside	O
a	O
category	B-Protocol
5	I-Protocol
or	O
above	O
cable	O
.	O
</s>
<s>
Each	O
network	B-Protocol
segment	I-Protocol
can	O
have	O
a	O
maximum	O
cabling	O
distance	O
of	O
.	O
</s>
<s>
Like	O
10BASE-T	B-Protocol
,	O
the	O
active	O
pairs	O
in	O
a	O
standard	O
connection	O
are	O
terminated	O
on	O
pins	O
1	O
,	O
2	O
,	O
3	O
and	O
6	O
.	O
</s>
<s>
Since	O
a	O
typical	O
category	B-Protocol
5	I-Protocol
cable	I-Protocol
contains	O
4	O
pairs	O
,	O
it	O
can	O
support	O
two	O
100BASE-TX	B-Protocol
links	O
with	O
a	O
wiring	O
adaptor	O
.	O
</s>
<s>
The	O
configuration	O
of	O
100BASE-TX	B-Protocol
networks	O
is	O
very	O
similar	O
to	O
10BASE-T	B-Protocol
.	O
</s>
<s>
When	O
used	O
to	O
build	O
a	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
,	O
the	O
devices	O
on	O
the	O
network	O
(	O
computers	O
,	O
printers	O
etc	O
.	O
)	O
</s>
<s>
are	O
typically	O
connected	O
to	O
a	O
hub	B-Protocol
or	O
switch	B-Protocol
,	O
creating	O
a	O
star	B-Architecture
network	I-Architecture
.	O
</s>
<s>
Alternatively	O
,	O
it	O
is	O
possible	O
to	O
connect	O
two	O
devices	O
directly	O
using	O
a	O
crossover	B-Protocol
cable	I-Protocol
.	O
</s>
<s>
With	O
today	O
's	O
equipment	O
,	O
crossover	B-Protocol
cables	I-Protocol
are	O
generally	O
not	O
needed	O
as	O
most	O
equipment	O
supports	O
auto-negotiation	O
along	O
with	O
auto	O
MDI-X	O
to	O
select	O
and	O
match	O
speed	O
,	O
duplex	O
and	O
pairing	O
.	O
</s>
<s>
With	O
100BASE-TX	B-Protocol
hardware	O
,	O
the	O
raw	O
bits	O
,	O
presented	O
4	O
bits	O
wide	O
clocked	O
at	O
25MHz	O
at	O
the	O
MII	O
,	O
go	O
through	O
4B5B	B-Protocol
binary	O
encoding	O
to	O
generate	O
a	O
series	O
of	O
0	O
and	O
1	O
symbols	O
clocked	O
at	O
a	O
125MHz	O
symbol	O
rate	O
.	O
</s>
<s>
The	O
4B5B	B-Protocol
encoding	O
provides	O
DC	O
equalization	O
and	O
spectrum	O
shaping	O
.	O
</s>
<s>
However	O
,	O
100BASE-TX	B-Protocol
introduces	O
an	O
additional	O
,	O
medium-dependent	O
sublayer	O
,	O
which	O
employs	O
MLT-3	B-Protocol
as	O
a	O
final	O
encoding	O
of	O
the	O
data	O
stream	O
before	O
transmission	O
,	O
resulting	O
in	O
a	O
maximum	O
fundamental	O
frequency	O
of	O
31.25MHz	O
.	O
</s>
<s>
The	O
procedure	O
is	O
borrowed	O
from	O
the	O
ANSI	O
X3.263	O
FDDI	B-Protocol
specifications	O
,	O
with	O
minor	O
changes	O
.	O
</s>
<s>
The	O
standard	O
is	O
intended	O
for	O
automotive	O
applications	O
or	O
when	O
Fast	B-Protocol
Ethernet	I-Protocol
is	O
to	O
be	O
integrated	O
into	O
another	O
application	O
.	O
</s>
<s>
In	O
100BASE-T2	O
,	O
standardized	O
in	O
IEEE	O
802.3y	O
,	O
the	O
data	O
is	O
transmitted	O
over	O
two	O
copper	O
pairs	O
,	O
but	O
these	O
pairs	O
are	O
only	O
required	O
to	O
be	O
category	O
3	O
rather	O
than	O
the	O
category	B-Protocol
5	I-Protocol
required	O
by	O
100BASE-TX	B-Protocol
.	O
</s>
<s>
The	O
4-bit	O
symbol	O
is	O
expanded	O
into	O
two	O
3-bit	O
symbols	O
through	O
a	O
non-trivial	O
scrambling	O
procedure	O
based	O
on	O
a	O
linear-feedback	B-Architecture
shift	I-Architecture
register	I-Architecture
.	O
</s>
<s>
The	O
final	O
mapping	O
from	O
symbols	O
to	O
PAM-5	B-Device
line	O
modulation	O
levels	O
obeys	O
the	O
table	O
on	O
the	O
right	O
.	O
</s>
<s>
100BASE-T4	O
was	O
an	O
early	O
implementation	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
.	O
</s>
<s>
It	O
requires	O
four	O
twisted	O
copper	O
pairs	O
of	O
voice	B-Protocol
grade	I-Protocol
twisted	I-Protocol
pair	I-Protocol
,	O
a	O
lower-performing	O
cable	O
compared	O
to	O
category	B-Protocol
5	I-Protocol
cable	I-Protocol
used	O
by	O
100BASE-TX	B-Protocol
.	O
</s>
<s>
One	O
pair	O
is	O
reserved	O
for	O
transmit	O
,	O
one	O
for	O
receive	O
,	O
and	O
the	O
remaining	O
two	O
switch	B-Protocol
direction	O
.	O
</s>
<s>
The	O
two	O
resulting	O
3-digit	O
base-3	O
symbols	O
are	O
sent	O
in	O
parallel	O
over	O
3	O
pairs	O
using	O
3-level	O
pulse-amplitude	B-Device
modulation	I-Device
(	O
PAM-3	O
)	O
.	O
</s>
<s>
Very	O
few	O
hubs	B-Protocol
were	O
released	O
with	O
100BASE-T4	O
support	O
.	O
</s>
<s>
Some	O
examples	O
include	O
the	O
3com	O
3C250-T4	O
Superstack	O
II	O
HUB	B-Protocol
100	O
,	O
IBM	O
8225	O
Fast	B-Protocol
Ethernet	I-Protocol
Stackable	O
Hub	B-Protocol
and	O
Intel	O
LinkBuilder	O
FMS	O
100	O
T4	O
.	O
</s>
<s>
The	O
same	O
applies	O
to	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
cards	O
.	O
</s>
<s>
Bridging	O
100BASE-T4	O
with	O
100BASE-TX	B-Protocol
required	O
additional	O
network	O
equipment	O
.	O
</s>
<s>
Proposed	O
and	O
marketed	O
by	O
Hewlett-Packard	O
,	O
100BaseVG	B-Protocol
was	O
an	O
alternative	O
design	O
using	O
category	O
3	O
cabling	O
and	O
a	O
token	O
concept	O
instead	O
of	O
CSMA/CD	O
.	O
</s>
<s>
It	O
was	O
slated	O
for	O
standardization	O
as	O
IEEE	B-Protocol
802.12	I-Protocol
but	O
it	O
quickly	O
vanished	O
when	O
switched	O
100BASE-TX	B-Protocol
became	O
popular	O
.	O
</s>
<s>
Fiber	O
variants	O
use	O
fiber-optic	B-Architecture
cable	I-Architecture
with	O
the	O
listed	O
interface	O
types	O
.	O
</s>
<s>
Interfaces	O
may	O
be	O
fixed	O
or	O
modular	O
,	O
often	O
as	O
small	B-Protocol
form-factor	I-Protocol
pluggable	I-Protocol
(	O
SFP	O
)	O
.	O
</s>
<s>
412	O
m	O
for	O
half-duplex	O
connections	O
to	O
ensure	O
collision	O
detection	O
;	O
specification	O
largely	O
derived	O
from	O
FDDI.Modal	O
bandwidth	O
:	O
800	O
MHz·km	O
rowspan	O
=	O
"	O
5	O
"	O
rowspan	O
=	O
"	O
5	O
"	O
rowspan	O
=	O
"	O
5	O
"	O
rowspan	O
=	O
"	O
5	O
"	O
SFP	O
2	O
1	O
1	O
vendor-specific	O
FP	O
laser	O
transmitterFull-duplexModal	O
bandwidth	O
:	O
800	O
MHz·km	O
rowspan	O
=	O
"	O
2	O
"	O
rowspan	O
=	O
"	O
2	O
"	O
rowspan	O
=	O
"	O
2	O
"	O
rowspan	O
=	O
"	O
2	O
"	O
rowspan	O
=	O
"	O
2	O
"	O
2	O
1	O
1	O
optics	O
sharable	O
with	O
10BASE-FL	O
,	O
thus	O
making	O
it	O
possible	O
to	O
have	O
an	O
auto-negotiation	O
scheme	O
and	O
use	O
10/100	B-Protocol
fiber	O
adapters	O
.	O
</s>
<s>
Fast	B-Protocol
Ethernet	I-Protocol
speed	O
is	O
not	O
available	O
on	O
all	O
SFP	B-Protocol
ports	I-Protocol
,	O
but	O
supported	O
by	O
some	O
devices	O
.	O
</s>
<s>
An	O
SFP	B-Protocol
port	I-Protocol
for	O
Gigabit	O
Ethernet	O
should	O
not	O
be	O
assumed	O
to	O
be	O
backwards	O
compatible	O
with	O
Fast	B-Protocol
Ethernet	I-Protocol
.	O
</s>
<s>
100BASE-X	B-Protocol
Ethernet	O
is	O
not	O
backward	O
compatible	O
with	O
10BASE-F	O
and	O
is	O
not	O
forward	O
compatible	O
with	O
1000BASE-X	O
.	O
</s>
<s>
100BASE-FX	O
is	O
a	O
version	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
over	O
optical	B-Architecture
fiber	I-Architecture
.	O
</s>
<s>
The	O
100BASE-FX	O
physical	B-Protocol
medium	I-Protocol
dependent	I-Protocol
(	O
PMD	O
)	O
sublayer	O
is	O
defined	O
by	O
FDDI	B-Protocol
's	O
PMD	O
,	O
so	O
100BASE-FX	O
is	O
not	O
compatible	O
with	O
10BASE-FL	O
,	O
the	O
10Mbit/s	O
version	O
over	O
optical	B-Architecture
fiber	I-Architecture
.	O
</s>
<s>
100BASE-FX	O
is	O
still	O
used	O
for	O
existing	O
installation	O
of	O
multimode	B-Device
fiber	I-Device
where	O
more	O
speed	O
is	O
not	O
required	O
,	O
like	O
industrial	O
automation	O
plants	O
.	O
</s>
<s>
100BASE-LFX	O
is	O
a	O
non-standard	O
term	O
to	O
refer	O
to	O
Fast	B-Protocol
Ethernet	I-Protocol
transmission	O
.	O
</s>
<s>
It	O
is	O
very	O
similar	O
to	O
100BASE-FX	O
but	O
achieves	O
longer	O
distances	O
up	O
to	O
4	O
–	O
5km	O
over	O
a	O
pair	O
of	O
multi-mode	B-Device
fibers	I-Device
through	O
the	O
use	O
of	O
Fabry	O
–	O
Pérot	O
laser	O
transmitter	O
running	O
on	O
1310nm	O
wavelength	O
.	O
</s>
<s>
100BASE-SX	O
is	O
a	O
version	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
over	O
optical	B-Architecture
fiber	I-Architecture
standardized	O
in	O
TIA/EIA	O
-785-1-2002	O
.	O
</s>
<s>
Because	O
it	O
uses	O
the	O
same	O
wavelength	O
as	O
10BASE-FL	O
,	O
the	O
10Mbit/s	O
version	O
of	O
Ethernet	O
over	O
optical	B-Architecture
fiber	I-Architecture
,	O
100BASE-SX	O
can	O
be	O
backward-compatible	O
with	O
10BASE-FL	O
.	O
</s>
<s>
100BASE-LX10	O
is	O
a	O
version	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
over	O
optical	B-Architecture
fiber	I-Architecture
standardized	O
in	O
802.3ah-2004	O
clause	O
58	O
.	O
</s>
<s>
100BASE-BX10	O
is	O
a	O
version	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
over	O
optical	B-Architecture
fiber	I-Architecture
standardized	O
in	O
802.3ah-2004	O
clause	O
58	O
.	O
</s>
<s>
100BASE-ZX	O
is	O
a	O
non-standard	O
but	O
multi-vendor	O
term	O
to	O
refer	O
to	O
Fast	B-Protocol
Ethernet	I-Protocol
transmission	O
using	O
1,550	O
nm	O
wavelength	O
to	O
achieve	O
distances	O
of	O
at	O
least	O
70km	O
over	O
single-mode	O
fiber	O
.	O
</s>
