<s>
A	O
collision	B-Protocol
domain	I-Protocol
is	O
a	O
network	B-Protocol
segment	I-Protocol
connected	O
by	O
a	O
shared	B-Protocol
medium	I-Protocol
or	O
through	O
repeaters	O
where	O
simultaneous	O
data	O
transmissions	O
collide	O
with	O
one	O
another	O
.	O
</s>
<s>
The	O
collision	B-Protocol
domain	I-Protocol
applies	O
particularly	O
in	O
wireless	B-General_Concept
networks	I-General_Concept
,	O
but	O
also	O
affected	O
early	O
versions	O
of	O
Ethernet	O
.	O
</s>
<s>
A	O
network	O
collision	O
occurs	O
when	O
more	O
than	O
one	O
device	O
attempts	O
to	O
send	O
a	O
packet	O
on	O
a	O
network	B-Protocol
segment	I-Protocol
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Members	O
of	O
a	O
collision	B-Protocol
domain	I-Protocol
may	O
be	O
involved	O
in	O
collisions	O
with	O
one	O
another	O
.	O
</s>
<s>
Devices	O
outside	O
the	O
collision	B-Protocol
domain	I-Protocol
do	O
not	O
have	O
collisions	O
with	O
those	O
inside	O
.	O
</s>
<s>
A	O
channel	O
access	O
method	O
dictates	O
that	O
only	O
one	O
device	O
in	O
the	O
collision	B-Protocol
domain	I-Protocol
may	O
transmit	O
at	O
any	O
one	O
time	O
,	O
and	O
the	O
other	O
devices	O
in	O
the	O
domain	O
listen	O
to	O
the	O
network	O
and	O
refrain	O
from	O
transmitting	O
while	O
others	O
are	O
already	O
transmitting	O
in	O
order	O
to	O
avoid	O
collisions	O
.	O
</s>
<s>
Because	O
only	O
one	O
device	O
may	O
be	O
transmitting	O
at	O
any	O
one	O
time	O
,	O
total	O
network	O
bandwidth	O
is	O
shared	O
among	O
all	O
devices	O
on	O
the	O
collision	B-Protocol
domain	I-Protocol
.	O
</s>
<s>
Collisions	O
also	O
decrease	O
network	O
efficiency	O
on	O
a	O
collision	B-Protocol
domain	I-Protocol
as	O
collisions	O
require	O
devices	O
to	O
abort	O
transmission	O
and	O
retransmit	O
at	O
a	O
later	O
time	O
.	O
</s>
<s>
Since	O
data	O
bits	O
are	O
propagated	O
at	O
a	O
finite	O
speed	O
,	O
simultaneously	O
is	O
to	O
be	O
defined	O
in	O
terms	O
of	O
the	O
size	O
of	O
the	O
collision	B-Protocol
domain	I-Protocol
and	O
the	O
minimum	O
packet	O
size	O
allowed	O
.	O
</s>
<s>
Unless	O
the	O
size	O
of	O
the	O
collision	B-Protocol
domain	I-Protocol
allows	O
the	O
initial	O
sender	O
to	O
receive	O
the	O
second	O
transmission	O
attempt	O
–	O
the	O
collision	O
–	O
within	O
the	O
time	O
it	O
takes	O
to	O
send	O
the	O
packet	O
,	O
he	O
would	O
neither	O
be	O
able	O
to	O
detect	O
the	O
collision	O
nor	O
to	O
repeat	O
the	O
transmission	O
this	O
is	O
called	O
a	O
late	O
collision	O
.	O
</s>
<s>
Early	O
Ethernet	O
variants	O
(	O
10BASE5	O
,	O
10BASE2	O
)	O
were	O
based	O
on	O
a	O
shared	O
wire	O
and	O
inherently	O
half-duplex	O
,	O
representing	O
a	O
single	O
,	O
potentially	O
large	O
collision	B-Protocol
domain	I-Protocol
.	O
</s>
<s>
Collision	B-Protocol
domains	I-Protocol
are	O
also	O
found	O
in	O
an	O
Ethernet	B-Protocol
hub	I-Protocol
or	O
repeater	O
environment	O
where	O
each	O
host	O
segment	O
connects	O
to	O
a	O
hub	B-Protocol
,	O
and	O
all	O
segments	O
represent	O
only	O
one	O
collision	B-Protocol
domain	I-Protocol
within	O
one	O
broadcast	B-Architecture
domain	I-Architecture
.	O
</s>
<s>
Collision	B-Protocol
domains	I-Protocol
are	O
also	O
found	O
in	O
other	O
shared	B-Protocol
medium	I-Protocol
networks	O
,	O
e.g.	O
</s>
<s>
wireless	B-General_Concept
networks	I-General_Concept
such	O
as	O
Wi-Fi	O
.	O
</s>
<s>
Modern	O
wired	O
networks	O
use	O
a	O
network	B-Protocol
switch	I-Protocol
to	O
reduce	O
or	O
eliminate	O
collisions	O
.	O
</s>
<s>
By	O
connecting	O
each	O
device	O
directly	O
to	O
a	O
port	O
on	O
the	O
switch	O
,	O
either	O
each	O
port	O
on	O
a	O
switch	O
becomes	O
its	O
own	O
collision	B-Protocol
domain	I-Protocol
(	O
in	O
the	O
case	O
of	O
half-duplex	O
links	O
)	O
,	O
or	O
the	O
possibility	O
of	O
collisions	O
is	O
eliminated	O
entirely	O
in	O
the	O
case	O
of	O
full-duplex	O
links	O
.	O
</s>
<s>
For	O
Gigabit	O
Ethernet	O
and	O
faster	O
,	O
no	O
hubs	B-Protocol
or	O
repeaters	O
exist	O
and	O
all	O
devices	O
require	O
full-duplex	O
links	O
.	O
</s>
<s>
Most	O
wireless	B-Architecture
LAN	I-Architecture
networks	I-Architecture
use	O
the	O
carrier-sense	O
multiple	O
access	O
with	O
collision	O
avoidance	O
(	O
CSMA/CA	O
)	O
method	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
requirements	O
of	O
a	O
shared	O
wire	O
medium	O
,	O
wireless	B-General_Concept
networks	I-General_Concept
add	O
the	O
hidden	B-General_Concept
node	I-General_Concept
problem	I-General_Concept
where	O
two	O
senders	O
ca	O
n't	O
hear	O
each	O
other	O
's	O
transmissions	O
,	O
but	O
they	O
cause	O
a	O
collision	O
at	O
the	O
receiver	O
between	O
them	O
.	O
</s>
<s>
A	O
central	O
coordination	O
is	O
another	O
means	O
of	O
solving	O
this	O
problem	O
for	O
a	O
collision	B-Protocol
domain	I-Protocol
.	O
</s>
<s>
This	O
technique	O
is	O
employed	O
by	O
Wireless	B-General_Concept
Multimedia	I-General_Concept
Extensions	I-General_Concept
.	O
</s>
