<s>
Network	B-Architecture
topology	I-Architecture
is	O
the	O
arrangement	O
of	O
the	O
elements	O
(	O
links	O
,	O
nodes	B-Protocol
,	O
etc	O
.	O
)	O
</s>
<s>
Network	B-Architecture
topology	I-Architecture
can	B-Protocol
be	O
used	O
to	O
define	O
or	O
describe	O
the	O
arrangement	O
of	O
various	O
types	O
of	O
telecommunication	O
networks	O
,	O
including	O
command	O
and	O
control	O
radio	O
networks	O
,	O
industrial	O
fieldbusses	O
and	O
computer	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
Network	B-Architecture
topology	I-Architecture
is	O
the	O
topological	O
structure	O
of	O
a	O
network	O
and	O
may	O
be	O
depicted	O
physically	O
or	O
logically	O
.	O
</s>
<s>
It	O
is	O
an	O
application	O
of	O
graph	O
theory	O
wherein	O
communicating	O
devices	O
are	O
modeled	O
as	O
nodes	B-Protocol
and	O
the	O
connections	O
between	O
the	O
devices	O
are	O
modeled	O
as	O
links	O
or	O
lines	O
between	O
the	O
nodes	B-Protocol
.	O
</s>
<s>
Physical	B-Architecture
topology	I-Architecture
is	O
the	O
placement	O
of	O
the	O
various	O
components	O
of	O
a	O
network	O
(	O
e.g.	O
,	O
device	O
location	O
and	O
cable	O
installation	O
)	O
,	O
while	O
logical	B-Architecture
topology	I-Architecture
illustrates	O
how	O
data	O
flows	O
within	O
a	O
network	O
.	O
</s>
<s>
Distances	O
between	O
nodes	B-Protocol
,	O
physical	O
interconnections	O
,	O
transmission	O
rates	O
,	O
or	O
signal	O
types	O
may	O
differ	O
between	O
two	O
different	O
networks	O
,	O
yet	O
their	O
logical	B-Architecture
topologies	I-Architecture
may	O
be	O
identical	O
.	O
</s>
<s>
A	O
network	O
’s	O
physical	B-Architecture
topology	I-Architecture
is	O
a	O
particular	O
concern	O
of	O
the	O
physical	B-Application
layer	I-Application
of	O
the	O
OSI	O
model	O
.	O
</s>
<s>
Examples	O
of	O
network	B-Architecture
topologies	I-Architecture
are	O
found	O
in	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
(	O
LAN	B-General_Concept
)	O
,	O
a	O
common	O
computer	B-Architecture
network	I-Architecture
installation	O
.	O
</s>
<s>
Any	O
given	O
node	B-Protocol
in	O
the	O
LAN	B-General_Concept
has	O
one	O
or	O
more	O
physical	B-Application
links	I-Application
to	O
other	O
devices	O
in	O
the	O
network	O
;	O
graphically	O
mapping	O
these	O
links	O
results	O
in	O
a	O
geometric	O
shape	O
that	O
can	B-Protocol
be	O
used	O
to	O
describe	O
the	O
physical	B-Architecture
topology	I-Architecture
of	O
the	O
network	O
.	O
</s>
<s>
A	O
wide	O
variety	O
of	O
physical	B-Architecture
topologies	I-Architecture
have	O
been	O
used	O
in	O
LANs	B-General_Concept
,	O
including	O
ring	B-Architecture
,	O
bus	B-Architecture
,	O
mesh	B-Architecture
and	O
star	B-Architecture
.	O
</s>
<s>
Conversely	O
,	O
mapping	O
the	O
data	B-Operating_System
flow	I-Operating_System
between	O
the	O
components	O
determines	O
the	O
logical	B-Architecture
topology	I-Architecture
of	O
the	O
network	O
.	O
</s>
<s>
In	O
comparison	O
,	O
Controller	B-Protocol
Area	I-Protocol
Networks	I-Protocol
,	O
common	O
in	O
vehicles	O
,	O
are	O
primarily	O
distributed	O
control	O
system	O
networks	O
of	O
one	O
or	O
more	O
controllers	O
interconnected	O
with	O
sensors	O
and	O
actuators	O
over	O
,	O
invariably	O
,	O
a	O
physical	O
bus	B-Architecture
topology	I-Architecture
.	O
</s>
<s>
Two	O
basic	O
categories	O
of	O
network	B-Architecture
topologies	I-Architecture
exist	O
,	O
physical	B-Architecture
topologies	I-Architecture
and	O
logical	B-Architecture
topologies	I-Architecture
.	O
</s>
<s>
The	O
transmission	O
medium	O
layout	O
used	O
to	O
link	O
devices	O
is	O
the	O
physical	B-Architecture
topology	I-Architecture
of	O
the	O
network	O
.	O
</s>
<s>
For	O
conductive	O
or	O
fiber	O
optical	O
mediums	O
,	O
this	O
refers	O
to	O
the	O
layout	O
of	O
cabling	O
,	O
the	O
locations	O
of	O
nodes	B-Protocol
,	O
and	O
the	O
links	O
between	O
the	O
nodes	B-Protocol
and	O
the	O
cabling	O
.	O
</s>
<s>
The	O
physical	B-Architecture
topology	I-Architecture
of	O
a	O
network	O
is	O
determined	O
by	O
the	O
capabilities	O
of	O
the	O
network	O
access	O
devices	O
and	O
media	O
,	O
the	O
level	O
of	O
control	O
or	O
fault	O
tolerance	O
desired	O
,	O
and	O
the	O
cost	O
associated	O
with	O
cabling	O
or	O
telecommunication	O
circuits	O
.	O
</s>
<s>
In	O
contrast	O
,	O
logical	B-Architecture
topology	I-Architecture
is	O
the	O
way	O
that	O
the	O
signals	O
act	O
on	O
the	O
network	O
media	O
,	O
or	O
the	O
way	O
that	O
the	O
data	O
passes	O
through	O
the	O
network	O
from	O
one	O
device	O
to	O
the	O
next	O
without	O
regard	O
to	O
the	O
physical	O
interconnection	O
of	O
the	O
devices	O
.	O
</s>
<s>
A	O
network	O
's	O
logical	B-Architecture
topology	I-Architecture
is	O
not	O
necessarily	O
the	O
same	O
as	O
its	O
physical	B-Architecture
topology	I-Architecture
.	O
</s>
<s>
For	O
example	O
,	O
the	O
original	O
twisted	B-Protocol
pair	I-Protocol
Ethernet	I-Protocol
using	O
repeater	B-Protocol
hubs	I-Protocol
was	O
a	O
logical	O
bus	B-Architecture
topology	I-Architecture
carried	O
on	O
a	O
physical	O
star	B-Architecture
topology	I-Architecture
.	O
</s>
<s>
Token	B-Device
Ring	I-Device
is	O
a	O
logical	O
ring	B-Architecture
topology	I-Architecture
,	O
but	O
is	O
wired	O
as	O
a	O
physical	O
star	B-Architecture
from	O
the	O
media	B-Device
access	I-Device
unit	I-Device
.	O
</s>
<s>
Physically	O
,	O
AFDX	B-Protocol
can	B-Protocol
be	O
a	O
cascaded	O
star	B-Architecture
topology	I-Architecture
of	O
multiple	O
dual	O
redundant	O
Ethernet	B-Protocol
switches	I-Protocol
;	O
however	O
,	O
the	O
AFDX	B-Protocol
Virtual	O
links	O
are	O
modeled	O
as	O
time-switched	B-Protocol
single-transmitter	O
bus	B-Architecture
connections	O
,	O
thus	O
following	O
the	O
safety	O
model	O
of	O
a	O
single-transmitter	O
bus	B-Architecture
topology	I-Architecture
previously	O
used	O
in	O
aircraft	O
.	O
</s>
<s>
Logical	B-Architecture
topologies	I-Architecture
are	O
often	O
closely	O
associated	O
with	O
media	B-Protocol
access	I-Protocol
control	I-Protocol
methods	O
and	O
protocols	O
.	O
</s>
<s>
Some	O
networks	O
are	O
able	O
to	O
dynamically	O
change	O
their	O
logical	B-Architecture
topology	I-Architecture
through	O
configuration	O
changes	O
to	O
their	O
routers	B-Protocol
and	O
switches	B-Protocol
.	O
</s>
<s>
The	O
transmission	O
media	O
(	O
often	O
referred	O
to	O
in	O
the	O
literature	O
as	O
the	O
physical	O
media	O
)	O
used	O
to	O
link	O
devices	O
to	O
form	O
a	O
computer	B-Architecture
network	I-Architecture
include	O
electrical	O
cables	O
(	O
Ethernet	O
,	O
HomePNA	B-Protocol
,	O
power	B-Device
line	I-Device
communication	I-Device
,	O
G.hn	B-General_Concept
)	O
,	O
optical	B-Architecture
fiber	I-Architecture
(	O
fiber-optic	B-Application
communication	I-Application
)	O
,	O
and	O
radio	O
waves	O
(	O
wireless	B-General_Concept
networking	I-General_Concept
)	O
.	O
</s>
<s>
In	O
the	O
OSI	O
model	O
,	O
these	O
are	O
defined	O
at	O
layers	O
1	O
and	O
2	O
—	O
the	O
physical	B-Application
layer	I-Application
and	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
.	O
</s>
<s>
A	O
widely	O
adopted	O
family	O
of	O
transmission	O
media	O
used	O
in	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
(	O
LAN	B-General_Concept
)	O
technology	O
is	O
collectively	O
known	O
as	O
Ethernet	O
.	O
</s>
<s>
Wireless	O
LAN	B-General_Concept
standards	O
(	O
e.g.	O
</s>
<s>
Power	B-Device
line	I-Device
communication	I-Device
uses	O
a	O
building	O
's	O
power	O
cabling	O
to	O
transmit	O
data	O
.	O
</s>
<s>
Coaxial	B-Protocol
cable	I-Protocol
is	O
widely	O
used	O
for	O
cable	O
television	O
systems	O
,	O
office	O
buildings	O
,	O
and	O
other	O
work-sites	O
for	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
.	O
</s>
<s>
The	O
insulation	O
between	O
the	O
conductors	O
helps	O
maintain	O
the	O
characteristic	O
impedance	O
of	O
the	O
cable	O
which	O
can	B-Protocol
help	O
improve	O
its	O
performance	O
.	O
</s>
<s>
ITU-T	B-General_Concept
G.hn	I-General_Concept
technology	O
uses	O
existing	O
home	O
wiring	O
(	O
coaxial	B-Protocol
cable	I-Protocol
,	O
phone	O
lines	O
and	O
power	B-Device
lines	I-Device
)	O
to	O
create	O
a	O
high-speed	O
(	O
up	O
to	O
1	O
Gigabit/s	O
)	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
.	O
</s>
<s>
Signal	O
traces	O
on	O
printed	O
circuit	O
boards	O
are	O
common	O
for	O
board-level	O
serial	O
communication	O
,	O
particularly	O
between	O
certain	O
types	O
integrated	O
circuits	O
,	O
a	O
common	O
example	O
being	O
SPI	B-Architecture
.	O
</s>
<s>
Several	O
serial	O
network	O
protocols	O
can	B-Protocol
be	O
deployed	O
without	O
shielded	O
or	O
twisted	O
pair	O
cabling	O
,	O
that	O
is	O
,	O
with	O
"	O
flat	O
"	O
or	O
"	O
ribbon	O
"	O
cable	O
,	O
or	O
a	O
hybrid	O
flat/twisted	O
ribbon	O
cable	O
,	O
should	O
EMC	O
,	O
length	O
,	O
and	O
bandwidth	O
constraints	O
permit	O
:	O
RS-232	O
,	O
RS-422	O
,	O
RS-485	O
,	O
CAN	B-Protocol
,	O
GPIB	O
,	O
SCSI	B-Architecture
,	O
etc	O
.	O
</s>
<s>
Computer	B-Architecture
network	I-Architecture
cabling	O
(	O
wired	B-Protocol
Ethernet	I-Protocol
as	O
defined	O
by	O
IEEE	O
802.3	O
)	O
consists	O
of	O
4	O
pairs	O
of	O
copper	O
cabling	O
that	O
can	B-Protocol
be	O
utilized	O
for	O
both	O
voice	O
and	O
data	O
transmission	O
.	O
</s>
<s>
An	O
optical	B-Architecture
fiber	I-Architecture
is	O
a	O
glass	O
fiber	O
.	O
</s>
<s>
Some	O
advantages	O
of	O
optical	B-Architecture
fibers	I-Architecture
over	O
metal	O
wires	O
are	O
very	O
low	O
transmission	O
loss	O
and	O
immunity	O
from	O
electrical	O
interference	O
.	O
</s>
<s>
Optical	B-Architecture
fibers	I-Architecture
can	B-Protocol
simultaneously	O
carry	O
multiple	O
wavelengths	O
of	O
light	O
,	O
which	O
greatly	O
increases	O
the	O
rate	O
that	O
data	O
can	B-Protocol
be	O
sent	O
,	O
and	O
helps	O
enable	O
data	O
rates	O
of	O
up	O
to	O
trillions	O
of	O
bits	O
per	O
second	O
.	O
</s>
<s>
Optic	B-Architecture
fibers	I-Architecture
can	B-Protocol
be	O
used	O
for	O
long	O
runs	O
of	O
cable	O
carrying	O
very	O
high	O
data	O
rates	O
,	O
and	O
are	O
used	O
for	O
undersea	O
communications	O
cables	O
to	O
interconnect	O
continents	O
.	O
</s>
<s>
Wireless	O
options	O
command	O
a	O
price	O
premium	O
that	O
can	B-Protocol
make	O
purchasing	O
wired	O
computers	O
,	O
printers	O
and	O
other	O
devices	O
a	O
financial	O
benefit	O
.	O
</s>
<s>
Radio	O
and	O
spread	B-Architecture
spectrum	I-Architecture
technologies	O
–	O
Wireless	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
use	O
a	O
high-frequency	O
radio	O
technology	O
similar	O
to	O
digital	O
cellular	O
and	O
a	O
low-frequency	O
radio	O
technology	O
.	O
</s>
<s>
Wireless	O
LANs	B-General_Concept
use	O
spread	B-Architecture
spectrum	I-Architecture
technology	O
to	O
enable	O
communication	O
between	O
multiple	O
devices	O
in	O
a	O
limited	O
area	O
.	O
</s>
<s>
IP	B-Protocol
over	I-Protocol
Avian	I-Protocol
Carriers	I-Protocol
was	O
a	O
humorous	O
April	O
fool	O
's	O
Request	O
for	O
Comments	O
,	O
issued	O
as	O
RFC	B-Protocol
1149	I-Protocol
.	O
</s>
<s>
Network	B-Protocol
nodes	I-Protocol
are	O
the	O
points	O
of	O
connection	O
of	O
the	O
transmission	O
medium	O
to	O
transmitters	O
and	O
receivers	O
of	O
the	O
electrical	O
,	O
optical	O
,	O
or	O
radio	O
signals	O
carried	O
in	O
the	O
medium	O
.	O
</s>
<s>
Nodes	B-Protocol
may	O
be	O
associated	O
with	O
a	O
computer	O
,	O
but	O
certain	O
types	O
may	O
have	O
only	O
a	O
microcontroller	O
at	O
a	O
node	B-Protocol
or	O
possibly	O
no	O
programmable	O
device	O
at	O
all	O
.	O
</s>
<s>
In	O
the	O
simplest	O
of	O
serial	O
arrangements	O
,	O
one	O
RS-232	O
transmitter	O
can	B-Protocol
be	O
connected	O
by	O
a	O
pair	O
of	O
wires	O
to	O
one	O
receiver	O
,	O
forming	O
two	O
nodes	B-Protocol
on	O
one	O
link	O
,	O
or	O
a	O
Point-to-Point	O
topology	B-Architecture
.	O
</s>
<s>
Some	O
protocols	O
permit	O
a	O
single	O
node	B-Protocol
to	O
only	O
either	O
transmit	O
or	O
receive	O
(	O
e.g.	O
,	O
ARINC	O
429	O
)	O
.	O
</s>
<s>
Other	O
protocols	O
have	O
nodes	B-Protocol
that	O
can	B-Protocol
both	O
transmit	O
and	O
receive	O
into	O
a	O
single	O
channel	O
(	O
e.g.	O
,	O
CAN	B-Protocol
can	B-Protocol
have	O
many	O
transceivers	O
connected	O
to	O
a	O
single	O
bus	B-Architecture
)	O
.	O
</s>
<s>
While	O
the	O
conventional	O
system	O
building	O
blocks	O
of	O
a	O
computer	B-Architecture
network	I-Architecture
include	O
network	B-Protocol
interface	I-Protocol
controllers	I-Protocol
(	O
NICs	O
)	O
,	O
repeaters	O
,	O
hubs	B-Protocol
,	O
bridges	B-Protocol
,	O
switches	B-Protocol
,	O
routers	B-Protocol
,	O
modems	B-Application
,	O
gateways	B-Application
,	O
and	O
firewalls	B-Application
,	O
most	O
address	O
network	O
concerns	O
beyond	O
the	O
physical	O
network	B-Architecture
topology	I-Architecture
and	O
may	O
be	O
represented	O
as	O
single	O
nodes	B-Protocol
on	O
a	O
particular	O
physical	O
network	B-Architecture
topology	I-Architecture
.	O
</s>
<s>
A	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
(	O
NIC	O
)	O
is	O
computer	B-Architecture
hardware	I-Architecture
that	O
provides	O
a	O
computer	O
with	O
the	O
ability	O
to	O
access	O
the	O
transmission	O
media	O
,	O
and	O
has	O
the	O
ability	O
to	O
process	O
low-level	O
network	O
information	O
.	O
</s>
<s>
The	O
NIC	O
responds	O
to	O
traffic	O
addressed	O
to	O
a	O
network	B-Protocol
address	I-Protocol
for	O
either	O
the	O
NIC	O
or	O
the	O
computer	O
as	O
a	O
whole	O
.	O
</s>
<s>
In	O
Ethernet	O
networks	O
,	O
each	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
has	O
a	O
unique	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
(	O
MAC	O
)	O
address	O
—	O
usually	O
stored	O
in	O
the	O
controller	O
's	O
permanent	O
memory	O
.	O
</s>
<s>
The	O
signal	O
may	O
be	O
reformed	O
or	O
retransmitted	B-Protocol
at	O
a	O
higher	O
power	O
level	O
,	O
to	O
the	O
other	O
side	O
of	O
an	O
obstruction	O
possibly	O
using	O
a	O
different	O
transmission	O
medium	O
,	O
so	O
that	O
the	O
signal	O
can	B-Protocol
cover	O
longer	O
distances	O
without	O
degradation	O
.	O
</s>
<s>
In	O
most	O
twisted	B-Protocol
pair	I-Protocol
Ethernet	I-Protocol
configurations	O
,	O
repeaters	O
are	O
required	O
for	O
cable	O
that	O
runs	O
longer	O
than	O
100	O
meters	O
.	O
</s>
<s>
With	O
fiber	B-Architecture
optics	I-Architecture
,	O
repeaters	O
can	B-Protocol
be	O
tens	O
or	O
even	O
hundreds	O
of	O
kilometers	O
apart	O
.	O
</s>
<s>
Repeaters	O
work	O
within	O
the	O
physical	B-Application
layer	I-Application
of	O
the	O
OSI	O
model	O
,	O
that	O
is	O
,	O
there	O
is	O
no	O
end-to-end	O
change	O
in	O
the	O
physical	O
protocol	O
across	O
the	O
repeater	O
,	O
or	O
repeater	O
pair	O
,	O
even	O
if	O
a	O
different	O
physical	B-Application
layer	I-Application
may	O
be	O
used	O
between	O
the	O
ends	O
of	O
the	O
repeater	O
,	O
or	O
repeater	O
pair	O
.	O
</s>
<s>
This	O
can	B-Protocol
cause	O
a	O
propagation	O
delay	O
that	O
affects	O
network	O
performance	O
and	O
may	O
affect	O
proper	O
function	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
many	O
network	O
architectures	O
limit	O
the	O
number	O
of	O
repeaters	O
that	O
can	B-Protocol
be	O
used	O
in	O
a	O
row	O
,	O
e.g.	O
,	O
the	O
Ethernet	O
5-4-3	B-Protocol
rule	I-Protocol
.	O
</s>
<s>
A	O
repeater	O
with	O
multiple	O
ports	B-Protocol
is	O
known	O
as	O
hub	B-Protocol
,	O
an	O
Ethernet	B-Protocol
hub	I-Protocol
in	O
Ethernet	O
networks	O
,	O
a	O
USB	B-Protocol
hub	B-Protocol
in	O
USB	B-Protocol
networks	O
.	O
</s>
<s>
USB	B-Protocol
networks	O
use	O
hubs	B-Protocol
to	O
form	O
tiered-star	B-Data_Structure
topologies	B-Architecture
.	O
</s>
<s>
Ethernet	B-Protocol
hubs	I-Protocol
and	O
repeaters	O
in	O
LANs	B-General_Concept
have	O
been	O
mostly	O
obsoleted	O
by	O
modern	O
switches	B-Protocol
.	O
</s>
<s>
A	O
network	B-Protocol
bridge	I-Protocol
connects	O
and	O
filters	O
traffic	O
between	O
two	O
network	B-Protocol
segments	I-Protocol
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
to	O
form	O
a	O
single	O
network	O
.	O
</s>
<s>
This	O
breaks	O
the	O
network	O
's	O
collision	O
domain	O
but	O
maintains	O
a	O
unified	O
broadcast	B-Operating_System
domain	O
.	O
</s>
<s>
Bridges	B-Protocol
come	O
in	O
three	O
basic	O
types	O
:	O
</s>
<s>
Remote	O
bridges	B-Protocol
:	O
Can	B-Protocol
be	O
used	O
to	O
create	O
a	O
wide	O
area	O
network	O
(	O
WAN	O
)	O
link	O
between	O
LANs	B-General_Concept
.	O
</s>
<s>
Remote	O
bridges	B-Protocol
,	O
where	O
the	O
connecting	O
link	O
is	O
slower	O
than	O
the	O
end	O
networks	O
,	O
largely	O
have	O
been	O
replaced	O
with	O
routers	B-Protocol
.	O
</s>
<s>
Wireless	B-Protocol
bridges	I-Protocol
:	O
Can	B-Protocol
be	O
used	O
to	O
join	O
LANs	B-General_Concept
or	O
connect	O
remote	O
devices	O
to	O
LANs	B-General_Concept
.	O
</s>
<s>
A	O
network	B-Protocol
switch	I-Protocol
is	O
a	O
device	O
that	O
forwards	O
and	O
filters	O
OSI	B-Protocol
layer	I-Protocol
2	I-Protocol
datagrams	B-Protocol
(	O
frames	B-Protocol
)	O
between	O
ports	B-Protocol
based	O
on	O
the	O
destination	O
MAC	O
address	O
in	O
each	O
frame	O
.	O
</s>
<s>
A	O
switch	O
is	O
distinct	O
from	O
a	O
hub	B-Protocol
in	O
that	O
it	O
only	O
forwards	O
the	O
frames	B-Protocol
to	O
the	O
physical	O
ports	B-Protocol
involved	O
in	O
the	O
communication	O
rather	O
than	O
all	O
ports	B-Protocol
connected	O
.	O
</s>
<s>
It	O
can	B-Protocol
be	O
thought	O
of	O
as	O
a	O
multi-port	O
bridge	O
.	O
</s>
<s>
It	O
learns	O
to	O
associate	O
physical	O
ports	B-Protocol
to	O
MAC	O
addresses	O
by	O
examining	O
the	O
source	O
addresses	O
of	O
received	O
frames	B-Protocol
.	O
</s>
<s>
If	O
an	O
unknown	O
destination	O
is	O
targeted	O
,	O
the	O
switch	O
broadcasts	B-Operating_System
to	O
all	O
ports	B-Protocol
but	O
the	O
source	O
.	O
</s>
<s>
Switches	B-Protocol
normally	O
have	O
numerous	O
ports	B-Protocol
,	O
facilitating	O
a	O
star	B-Architecture
topology	I-Architecture
for	O
devices	O
,	O
and	O
cascading	O
additional	O
switches	B-Protocol
.	O
</s>
<s>
Multi-layer	O
switches	B-Protocol
are	O
capable	O
of	O
routing	O
based	O
on	O
layer	O
3	O
addressing	O
or	O
additional	O
logical	O
levels	O
.	O
</s>
<s>
The	O
term	O
switch	O
is	O
often	O
used	O
loosely	O
to	O
include	O
devices	O
such	O
as	O
routers	B-Protocol
and	O
bridges	B-Protocol
,	O
as	O
well	O
as	O
devices	O
that	O
may	O
distribute	O
traffic	O
based	O
on	O
load	O
or	O
based	O
on	O
application	O
content	O
(	O
e.g.	O
,	O
a	O
Web	O
URL	O
identifier	O
)	O
.	O
</s>
<s>
A	O
router	B-Protocol
is	O
an	O
internetworking	B-Architecture
device	O
that	O
forwards	O
packets	B-Protocol
between	O
networks	O
by	O
processing	O
the	O
routing	O
information	O
included	O
in	O
the	O
packet	B-Protocol
or	O
datagram	B-Protocol
(	O
Internet	O
protocol	O
information	O
from	O
layer	O
3	O
)	O
.	O
</s>
<s>
The	O
routing	O
information	O
is	O
often	O
processed	O
in	O
conjunction	O
with	O
the	O
routing	B-Protocol
table	I-Protocol
(	O
or	O
forwarding	O
table	O
)	O
.	O
</s>
<s>
A	O
router	B-Protocol
uses	O
its	O
routing	B-Protocol
table	I-Protocol
to	O
determine	O
where	O
to	O
forward	O
packets	B-Protocol
.	O
</s>
<s>
A	O
destination	O
in	O
a	O
routing	B-Protocol
table	I-Protocol
can	B-Protocol
include	O
a	O
"	O
null	O
"	O
interface	O
,	O
also	O
known	O
as	O
the	O
"	O
black	O
hole	O
"	O
interface	O
because	O
data	O
can	B-Protocol
go	O
into	O
it	O
,	O
however	O
,	O
no	O
further	O
processing	O
is	O
done	O
for	O
said	O
data	O
,	O
i.e.	O
</s>
<s>
the	O
packets	B-Protocol
are	O
dropped	O
.	O
</s>
<s>
Modems	B-Application
(	O
MOdulator-DEModulator	O
)	O
are	O
used	O
to	O
connect	O
network	B-Protocol
nodes	I-Protocol
via	O
wire	O
not	O
originally	O
designed	O
for	O
digital	B-Architecture
network	I-Architecture
traffic	O
,	O
or	O
for	O
wireless	O
.	O
</s>
<s>
To	O
do	O
this	O
one	O
or	O
more	O
carrier	O
signals	O
are	O
modulated	B-Application
by	O
the	O
digital	O
signal	O
to	O
produce	O
an	O
analog	O
signal	O
that	O
can	B-Protocol
be	O
tailored	O
to	O
give	O
the	O
required	O
properties	O
for	O
transmission	O
.	O
</s>
<s>
Modems	B-Application
are	O
commonly	O
used	O
for	O
telephone	O
lines	O
,	O
using	O
a	O
digital	O
subscriber	O
line	O
technology	O
.	O
</s>
<s>
A	O
firewall	B-Application
is	O
a	O
network	O
device	O
for	O
controlling	O
network	O
security	O
and	O
access	O
rules	O
.	O
</s>
<s>
Firewalls	B-Application
are	O
typically	O
configured	O
to	O
reject	O
access	O
requests	O
from	O
unrecognized	O
sources	O
while	O
allowing	O
actions	O
from	O
recognized	O
ones	O
.	O
</s>
<s>
The	O
vital	O
role	O
firewalls	B-Application
play	O
in	O
network	O
security	O
grows	O
in	O
parallel	O
with	O
the	O
constant	O
increase	O
in	O
cyber	O
attacks	O
.	O
</s>
<s>
The	O
study	O
of	O
network	B-Architecture
topology	I-Architecture
recognizes	O
eight	O
basic	O
topologies	B-Architecture
:	O
point-to-point	O
,	O
bus	B-Architecture
,	O
star	B-Architecture
,	O
ring	B-Architecture
or	O
circular	O
,	O
mesh	B-Architecture
,	O
tree	O
,	O
hybrid	O
,	O
or	O
daisy	B-Application
chain	I-Application
.	O
</s>
<s>
The	O
simplest	O
topology	B-Architecture
with	O
a	O
dedicated	O
link	O
between	O
two	O
endpoints	O
.	O
</s>
<s>
Easiest	O
to	O
understand	O
,	O
of	O
the	O
variations	O
of	O
point-to-point	O
topology	B-Architecture
,	O
is	O
a	O
point-to-point	O
communication	O
channel	O
that	O
appears	O
,	O
to	O
the	O
user	O
,	O
to	O
be	O
permanently	O
associated	O
with	O
the	O
two	O
endpoints	O
.	O
</s>
<s>
A	O
child	O
's	O
tin	O
can	B-Protocol
telephone	O
is	O
one	O
example	O
of	O
a	O
physical	O
dedicated	O
channel	O
.	O
</s>
<s>
Using	O
circuit-switching	B-Protocol
or	O
packet-switching	B-Protocol
technologies	O
,	O
a	O
point-to-point	O
circuit	O
can	B-Protocol
be	O
set	O
up	O
dynamically	O
and	O
dropped	O
when	O
no	O
longer	O
needed	O
.	O
</s>
<s>
Switched	O
point-to-point	O
topologies	B-Architecture
are	O
the	O
basic	O
model	O
of	O
conventional	O
telephony	O
.	O
</s>
<s>
Daisy	B-Application
chaining	I-Application
is	O
accomplished	O
by	O
connecting	O
each	O
computer	O
in	O
series	O
to	O
the	O
next	O
.	O
</s>
<s>
A	O
daisy-chained	O
network	O
can	B-Protocol
take	O
two	O
basic	O
forms	O
:	O
linear	O
and	O
ring	B-Architecture
.	O
</s>
<s>
A	O
linear	B-Architecture
topology	I-Architecture
puts	O
a	O
two-way	O
link	O
between	O
one	O
computer	O
and	O
the	O
next	O
.	O
</s>
<s>
By	O
connecting	O
the	O
computers	O
at	O
each	O
end	O
of	O
the	O
chain	O
,	O
a	O
ring	B-Architecture
topology	I-Architecture
can	B-Protocol
be	O
formed	O
.	O
</s>
<s>
When	O
a	O
node	B-Protocol
sends	O
a	O
message	O
,	O
the	O
message	O
is	O
processed	O
by	O
each	O
computer	O
in	O
the	O
ring	B-Architecture
.	O
</s>
<s>
An	O
advantage	O
of	O
the	O
ring	B-Architecture
is	O
that	O
the	O
number	O
of	O
transmitters	O
and	O
receivers	O
can	B-Protocol
be	O
cut	O
in	O
half	O
.	O
</s>
<s>
Alternatively	O
,	O
the	O
ring	B-Architecture
can	B-Protocol
be	O
used	O
to	O
improve	O
fault	O
tolerance	O
.	O
</s>
<s>
If	O
the	O
ring	B-Architecture
breaks	O
at	O
a	O
particular	O
link	O
then	O
the	O
transmission	O
can	B-Protocol
be	O
sent	O
via	O
the	O
reverse	O
path	O
thereby	O
ensuring	O
that	O
all	O
nodes	B-Protocol
are	O
always	O
connected	O
in	O
the	O
case	O
of	O
a	O
single	O
failure	O
.	O
</s>
<s>
In	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
using	O
bus	B-Architecture
topology	I-Architecture
,	O
each	O
node	B-Protocol
is	O
connected	O
by	O
interface	O
connectors	O
to	O
a	O
single	O
central	O
cable	O
.	O
</s>
<s>
This	O
is	O
the	O
'	O
bus	B-Architecture
 '	O
,	O
also	O
referred	O
to	O
as	O
the	O
backbone	B-General_Concept
,	O
or	O
trunk	O
–	O
all	O
data	O
transmission	O
between	O
nodes	B-Protocol
in	O
the	O
network	O
is	O
transmitted	O
over	O
this	O
common	O
transmission	O
medium	O
and	O
is	O
able	O
to	O
be	O
received	O
by	O
all	O
nodes	B-Protocol
in	O
the	O
network	O
simultaneously	O
.	O
</s>
<s>
A	O
signal	O
containing	O
the	O
address	O
of	O
the	O
intended	O
receiving	O
machine	O
travels	O
from	O
a	O
source	O
machine	O
in	O
both	O
directions	O
to	O
all	O
machines	O
connected	O
to	O
the	O
bus	B-Architecture
until	O
it	O
finds	O
the	O
intended	O
recipient	O
,	O
which	O
then	O
accepts	O
the	O
data	O
.	O
</s>
<s>
Since	O
the	O
bus	B-Architecture
topology	I-Architecture
consists	O
of	O
only	O
one	O
wire	O
it	O
is	O
less	O
expensive	O
to	O
implement	O
than	O
other	O
topologies	B-Architecture
,	O
but	O
the	O
savings	O
are	O
offset	O
by	O
the	O
higher	O
cost	O
of	O
managing	O
the	O
network	O
.	O
</s>
<s>
Additionally	O
,	O
since	O
the	O
network	O
is	O
dependent	O
on	O
the	O
single	O
cable	O
,	O
it	O
can	B-Protocol
be	O
the	O
single	B-Architecture
point	I-Architecture
of	I-Architecture
failure	I-Architecture
of	O
the	O
network	O
.	O
</s>
<s>
In	O
this	O
topology	B-Architecture
data	O
being	O
transferred	O
may	O
be	O
accessed	O
by	O
any	O
node	B-Protocol
.	O
</s>
<s>
In	O
a	O
linear	O
bus	B-Architecture
network	I-Architecture
,	O
all	O
of	O
the	O
nodes	B-Protocol
of	O
the	O
network	O
are	O
connected	O
to	O
a	O
common	O
transmission	O
medium	O
which	O
has	O
just	O
two	O
endpoints	O
.	O
</s>
<s>
When	O
the	O
electrical	O
signal	O
reaches	O
the	O
end	O
of	O
the	O
bus	B-Architecture
,	O
the	O
signal	O
is	O
reflected	O
back	O
down	O
the	O
line	O
,	O
causing	O
unwanted	O
interference	O
.	O
</s>
<s>
To	O
prevent	O
this	O
,	O
the	O
two	O
endpoints	O
of	O
the	O
bus	B-Architecture
are	O
normally	O
terminated	O
with	O
a	O
device	O
called	O
a	O
terminator	O
.	O
</s>
<s>
In	O
a	O
distributed	O
bus	B-Architecture
network	I-Architecture
,	O
all	O
of	O
the	O
nodes	B-Protocol
of	O
the	O
network	O
are	O
connected	O
to	O
a	O
common	O
transmission	O
medium	O
with	O
more	O
than	O
two	O
endpoints	O
,	O
created	O
by	O
adding	O
branches	O
to	O
the	O
main	O
section	O
of	O
the	O
transmission	O
medium	O
–	O
the	O
physical	O
distributed	O
bus	B-Architecture
topology	I-Architecture
functions	O
in	O
exactly	O
the	O
same	O
fashion	O
as	O
the	O
physical	O
linear	B-Architecture
bus	I-Architecture
topology	I-Architecture
because	O
all	O
nodes	B-Protocol
share	O
a	O
common	O
transmission	O
medium	O
.	O
</s>
<s>
In	O
star	B-Architecture
topology	I-Architecture
,	O
every	O
peripheral	O
node	B-Protocol
(	O
computer	O
workstation	O
or	O
any	O
other	O
peripheral	O
)	O
is	O
connected	O
to	O
a	O
central	O
node	B-Protocol
called	O
a	O
hub	B-Protocol
or	O
switch	O
.	O
</s>
<s>
The	O
hub	B-Protocol
is	O
the	O
server	O
and	O
the	O
peripherals	O
are	O
the	O
clients	O
.	O
</s>
<s>
The	O
network	O
does	O
not	O
necessarily	O
have	O
to	O
resemble	O
a	O
star	B-Architecture
to	O
be	O
classified	O
as	O
a	O
star	B-Architecture
network	I-Architecture
,	O
but	O
all	O
of	O
the	O
peripheral	O
nodes	B-Protocol
on	O
the	O
network	O
must	O
be	O
connected	O
to	O
one	O
central	O
hub	B-Protocol
.	O
</s>
<s>
All	O
traffic	O
that	O
traverses	O
the	O
network	O
passes	O
through	O
the	O
central	O
hub	B-Protocol
,	O
which	O
acts	O
as	O
a	O
signal	O
repeater	O
.	O
</s>
<s>
The	O
star	B-Architecture
topology	I-Architecture
is	O
considered	O
the	O
easiest	O
topology	B-Architecture
to	O
design	O
and	O
implement	O
.	O
</s>
<s>
One	O
advantage	O
of	O
the	O
star	B-Architecture
topology	I-Architecture
is	O
the	O
simplicity	O
of	O
adding	O
additional	O
nodes	B-Protocol
.	O
</s>
<s>
The	O
primary	O
disadvantage	O
of	O
the	O
star	B-Architecture
topology	I-Architecture
is	O
that	O
the	O
hub	B-Protocol
represents	O
a	O
single	B-Architecture
point	I-Architecture
of	I-Architecture
failure	I-Architecture
.	O
</s>
<s>
Also	O
,	O
since	O
all	O
peripheral	O
communication	O
must	O
flow	O
through	O
the	O
central	O
hub	B-Protocol
,	O
the	O
aggregate	O
central	O
bandwidth	O
forms	O
a	O
network	O
bottleneck	O
for	O
large	O
clusters	O
.	O
</s>
<s>
The	O
extended	O
star	B-Architecture
network	I-Architecture
topology	I-Architecture
extends	O
a	O
physical	O
star	B-Architecture
topology	I-Architecture
by	O
one	O
or	O
more	O
repeaters	O
between	O
the	O
central	O
node	B-Protocol
and	O
the	O
peripheral	O
(	O
or	O
'	O
spoke	O
 '	O
)	O
nodes	B-Protocol
.	O
</s>
<s>
The	O
repeaters	O
are	O
used	O
to	O
extend	O
the	O
maximum	O
transmission	O
distance	O
of	O
the	O
physical	B-Application
layer	I-Application
,	O
the	O
point-to-point	O
distance	O
between	O
the	O
central	O
node	B-Protocol
and	O
the	O
peripheral	O
nodes	B-Protocol
.	O
</s>
<s>
Repeaters	O
allow	O
greater	O
transmission	O
distance	O
,	O
further	O
than	O
would	O
be	O
possible	O
using	O
just	O
the	O
transmitting	O
power	O
of	O
the	O
central	O
node	B-Protocol
.	O
</s>
<s>
The	O
use	O
of	O
repeaters	O
can	B-Protocol
also	O
overcome	O
limitations	O
from	O
the	O
standard	O
upon	O
which	O
the	O
physical	B-Application
layer	I-Application
is	O
based	O
.	O
</s>
<s>
A	O
physical	O
extended	O
star	B-Architecture
topology	I-Architecture
in	O
which	O
repeaters	O
are	O
replaced	O
with	O
hubs	B-Protocol
or	O
switches	B-Protocol
is	O
a	O
type	O
of	O
hybrid	O
network	B-Architecture
topology	I-Architecture
and	O
is	O
referred	O
to	O
as	O
a	O
physical	O
hierarchical	O
star	B-Architecture
topology	I-Architecture
,	O
although	O
some	O
texts	O
make	O
no	O
distinction	O
between	O
the	O
two	O
topologies	B-Architecture
.	O
</s>
<s>
A	O
physical	O
hierarchical	O
star	B-Architecture
topology	I-Architecture
can	B-Protocol
also	O
be	O
referred	O
as	O
a	O
tier-star	O
topology	O
.	O
</s>
<s>
This	O
topology	B-Architecture
differs	O
from	O
a	O
tree	B-Data_Structure
topology	I-Data_Structure
in	O
the	O
way	O
star	B-Architecture
networks	I-Architecture
are	O
connected	O
together	O
.	O
</s>
<s>
A	O
tier-star	O
topology	O
uses	O
a	O
central	O
node	B-Protocol
,	O
while	O
a	O
tree	B-Data_Structure
topology	I-Data_Structure
uses	O
a	O
central	O
bus	B-Architecture
and	O
can	B-Protocol
also	O
be	O
referred	O
as	O
a	O
star-bus	B-Data_Structure
network	I-Data_Structure
.	O
</s>
<s>
A	O
distributed	O
star	B-Architecture
is	O
a	O
network	B-Architecture
topology	I-Architecture
that	O
is	O
composed	O
of	O
individual	O
networks	O
that	O
are	O
based	O
upon	O
the	O
physical	O
star	B-Architecture
topology	I-Architecture
connected	O
in	O
a	O
linear	O
fashion	O
–	O
i.e.	O
,	O
'	O
daisy-chained	O
'	O
–	O
with	O
no	O
central	O
or	O
top	O
level	O
connection	O
point	O
(	O
e.g.	O
,	O
two	O
or	O
more	O
'	O
stacked	O
 '	O
hubs	B-Protocol
,	O
along	O
with	O
their	O
associated	O
star	B-Architecture
connected	O
nodes	B-Protocol
or	O
'	O
spokes	O
 '	O
)	O
.	O
</s>
<s>
A	O
ring	B-Architecture
topology	I-Architecture
is	O
a	O
daisy	B-Application
chain	I-Application
in	O
a	O
closed	O
loop	O
.	O
</s>
<s>
Data	O
travels	O
around	O
the	O
ring	B-Architecture
in	O
one	O
direction	O
.	O
</s>
<s>
When	O
one	O
node	B-Protocol
sends	O
data	O
to	O
another	O
,	O
the	O
data	O
passes	O
through	O
each	O
intermediate	B-Protocol
node	I-Protocol
on	O
the	O
ring	B-Architecture
until	O
it	O
reaches	O
its	O
destination	O
.	O
</s>
<s>
The	O
intermediate	B-Protocol
nodes	I-Protocol
repeat	O
(	O
retransmit	O
)	O
the	O
data	O
to	O
keep	O
the	O
signal	O
strong	O
.	O
</s>
<s>
Every	O
node	B-Protocol
is	O
a	O
peer	O
;	O
there	O
is	O
no	O
hierarchical	O
relationship	O
of	O
clients	O
and	O
servers	O
.	O
</s>
<s>
If	O
one	O
node	B-Protocol
is	O
unable	O
to	O
retransmit	O
data	O
,	O
it	O
severs	O
communication	O
between	O
the	O
nodes	B-Protocol
before	O
and	O
after	O
it	O
in	O
the	O
bus	B-Architecture
.	O
</s>
<s>
When	O
the	O
load	O
on	O
the	O
network	O
increases	O
,	O
its	O
performance	O
is	O
better	O
than	O
bus	B-Architecture
topology	I-Architecture
.	O
</s>
<s>
Aggregate	O
network	O
bandwidth	O
is	O
bottlenecked	O
by	O
the	O
weakest	O
link	O
between	O
two	O
nodes	B-Protocol
.	O
</s>
<s>
In	O
a	O
fully	O
connected	O
network	O
,	O
all	O
nodes	B-Protocol
are	O
interconnected	O
.	O
</s>
<s>
The	O
simplest	O
fully	O
connected	O
network	O
is	O
a	O
two-node	O
network	O
.	O
</s>
<s>
A	O
fully	O
connected	O
network	O
does	O
n't	O
need	O
to	O
use	O
packet	B-Protocol
switching	I-Protocol
or	O
broadcasting	B-Operating_System
.	O
</s>
<s>
However	O
,	O
since	O
the	O
number	O
of	O
connections	O
grows	O
quadratically	O
with	O
the	O
number	O
of	O
nodes	B-Protocol
:	O
</s>
<s>
This	O
kind	O
of	O
topology	B-Architecture
does	O
not	O
trip	O
and	O
affect	O
other	O
nodes	B-Protocol
in	O
the	O
network	O
.	O
</s>
<s>
In	O
a	O
partially	O
connected	O
network	O
,	O
certain	O
nodes	B-Protocol
are	O
connected	O
to	O
exactly	O
one	O
other	O
node	B-Protocol
;	O
but	O
some	O
nodes	B-Protocol
are	O
connected	O
to	O
two	O
or	O
more	O
other	O
nodes	B-Protocol
with	O
a	O
point-to-point	O
link	O
.	O
</s>
<s>
This	O
makes	O
it	O
possible	O
to	O
make	O
use	O
of	O
some	O
of	O
the	O
redundancy	O
of	O
mesh	B-Architecture
topology	I-Architecture
that	O
is	O
physically	O
fully	O
connected	O
,	O
without	O
the	O
expense	O
and	O
complexity	O
required	O
for	O
a	O
connection	O
between	O
every	O
node	B-Protocol
in	O
the	O
network	O
.	O
</s>
<s>
Hybrid	O
topology	B-Architecture
is	O
also	O
known	O
as	O
hybrid	O
network	O
.	O
</s>
<s>
Hybrid	O
networks	O
combine	O
two	O
or	O
more	O
topologies	B-Architecture
in	O
such	O
a	O
way	O
that	O
the	O
resulting	O
network	O
does	O
not	O
exhibit	O
one	O
of	O
the	O
standard	O
topologies	B-Architecture
(	O
e.g.	O
,	O
bus	B-Architecture
,	O
star	B-Architecture
,	O
ring	B-Architecture
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
tree	B-Data_Structure
network	I-Data_Structure
(	O
or	O
star-bus	B-Data_Structure
network	I-Data_Structure
)	O
is	O
a	O
hybrid	O
topology	B-Architecture
in	O
which	O
star	B-Architecture
networks	I-Architecture
are	O
interconnected	O
via	O
bus	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
However	O
,	O
a	O
tree	B-Data_Structure
network	I-Data_Structure
connected	O
to	O
another	O
tree	B-Data_Structure
network	I-Data_Structure
is	O
still	O
topologically	O
a	O
tree	B-Data_Structure
network	I-Data_Structure
,	O
not	O
a	O
distinct	O
network	O
type	O
.	O
</s>
<s>
A	O
hybrid	O
topology	B-Architecture
is	O
always	O
produced	O
when	O
two	O
different	O
basic	O
network	B-Architecture
topologies	I-Architecture
are	O
connected	O
.	O
</s>
<s>
A	O
star-ring	O
network	O
consists	O
of	O
two	O
or	O
more	O
ring	B-Architecture
networks	I-Architecture
connected	O
using	O
a	O
multistation	B-Device
access	I-Device
unit	I-Device
(	O
MAU	O
)	O
as	O
a	O
centralized	O
hub	B-Protocol
.	O
</s>
<s>
Snowflake	O
topology	B-Architecture
is	O
a	O
star	B-Architecture
network	I-Architecture
of	O
star	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
Two	O
other	O
hybrid	O
network	O
types	O
are	O
hybrid	O
mesh	B-Architecture
and	O
hierarchical	O
star	B-Architecture
.	O
</s>
<s>
The	O
star	B-Architecture
topology	I-Architecture
reduces	O
the	O
probability	O
of	O
a	O
network	O
failure	O
by	O
connecting	O
all	O
of	O
the	O
peripheral	O
nodes	B-Protocol
(	O
computers	O
,	O
etc	O
.	O
)	O
</s>
<s>
to	O
a	O
central	O
node	B-Protocol
.	O
</s>
<s>
When	O
the	O
physical	O
star	B-Architecture
topology	I-Architecture
is	O
applied	O
to	O
a	O
logical	O
bus	B-Architecture
network	I-Architecture
such	O
as	O
Ethernet	O
,	O
this	O
central	O
node	B-Protocol
(	O
traditionally	O
a	O
hub	B-Protocol
)	O
rebroadcasts	O
all	O
transmissions	O
received	O
from	O
any	O
peripheral	O
node	B-Protocol
to	O
all	O
peripheral	O
nodes	B-Protocol
on	O
the	O
network	O
,	O
sometimes	O
including	O
the	O
originating	O
node	B-Protocol
.	O
</s>
<s>
All	O
peripheral	O
nodes	B-Protocol
may	O
thus	O
communicate	O
with	O
all	O
others	O
by	O
transmitting	O
to	O
,	O
and	O
receiving	O
from	O
,	O
the	O
central	O
node	B-Protocol
only	O
.	O
</s>
<s>
The	O
failure	O
of	O
a	O
transmission	O
line	O
linking	O
any	O
peripheral	O
node	B-Protocol
to	O
the	O
central	O
node	B-Protocol
will	O
result	O
in	O
the	O
isolation	O
of	O
that	O
peripheral	O
node	B-Protocol
from	O
all	O
others	O
,	O
but	O
the	O
remaining	O
peripheral	O
nodes	B-Protocol
will	O
be	O
unaffected	O
.	O
</s>
<s>
However	O
,	O
the	O
disadvantage	O
is	O
that	O
the	O
failure	O
of	O
the	O
central	O
node	B-Protocol
will	O
cause	O
the	O
failure	O
of	O
all	O
of	O
the	O
peripheral	O
nodes	B-Protocol
.	O
</s>
<s>
If	O
the	O
central	O
node	B-Protocol
is	O
passive	O
,	O
the	O
originating	O
node	B-Protocol
must	O
be	O
able	O
to	O
tolerate	O
the	O
reception	O
of	O
an	O
echo	O
of	O
its	O
own	O
transmission	O
,	O
delayed	O
by	O
the	O
two-way	O
round	O
trip	O
transmission	O
time	O
(	O
i.e.	O
</s>
<s>
to	O
and	O
from	O
the	O
central	O
node	B-Protocol
)	O
plus	O
any	O
delay	O
generated	O
in	O
the	O
central	O
node	B-Protocol
.	O
</s>
<s>
An	O
active	B-Protocol
star	I-Protocol
network	O
has	O
an	O
active	O
central	O
node	B-Protocol
that	O
usually	O
has	O
the	O
means	O
to	O
prevent	O
echo-related	O
problems	O
.	O
</s>
<s>
A	O
tree	B-Data_Structure
topology	I-Data_Structure
(	O
a.k.a.	O
</s>
<s>
hierarchical	B-Data_Structure
topology	I-Data_Structure
)	O
can	B-Protocol
be	O
viewed	O
as	O
a	O
collection	O
of	O
star	B-Architecture
networks	I-Architecture
arranged	O
in	O
a	O
hierarchy	O
.	O
</s>
<s>
This	O
tree	B-Data_Structure
structure	I-Data_Structure
has	O
individual	O
peripheral	O
nodes	B-Protocol
(	O
e.g.	O
</s>
<s>
leaves	O
)	O
which	O
are	O
required	O
to	O
transmit	O
to	O
and	O
receive	O
from	O
one	O
other	O
node	B-Protocol
only	O
and	O
are	O
not	O
required	O
to	O
act	O
as	O
repeaters	O
or	O
regenerators	O
.	O
</s>
<s>
Unlike	O
the	O
star	B-Architecture
network	I-Architecture
,	O
the	O
functionality	O
of	O
the	O
central	O
node	B-Protocol
may	O
be	O
distributed	O
.	O
</s>
<s>
As	O
in	O
the	O
conventional	O
star	B-Architecture
network	I-Architecture
,	O
individual	O
nodes	B-Protocol
may	O
thus	O
still	O
be	O
isolated	O
from	O
the	O
network	O
by	O
a	O
single-point	B-Architecture
failure	I-Architecture
of	O
a	O
transmission	O
path	O
to	O
the	O
node	B-Protocol
.	O
</s>
<s>
If	O
a	O
link	O
connecting	O
a	O
leaf	O
fails	O
,	O
that	O
leaf	O
is	O
isolated	O
;	O
if	O
a	O
connection	O
to	O
a	O
non-leaf	O
node	B-Protocol
fails	O
,	O
an	O
entire	O
section	O
of	O
the	O
network	O
becomes	O
isolated	O
from	O
the	O
rest	O
.	O
</s>
<s>
To	O
alleviate	O
the	O
amount	O
of	O
network	O
traffic	O
that	O
comes	O
from	O
broadcasting	B-Operating_System
all	O
signals	O
to	O
all	O
nodes	B-Protocol
,	O
more	O
advanced	O
central	O
nodes	B-Protocol
were	O
developed	O
that	O
are	O
able	O
to	O
keep	O
track	O
of	O
the	O
identities	O
of	O
the	O
nodes	B-Protocol
that	O
are	O
connected	O
to	O
the	O
network	O
.	O
</s>
<s>
These	O
network	B-Protocol
switches	I-Protocol
will	O
"	O
learn	O
"	O
the	O
layout	O
of	O
the	O
network	O
by	O
"	O
listening	O
"	O
on	O
each	O
port	O
during	O
normal	O
data	O
transmission	O
,	O
examining	O
the	O
data	B-Protocol
packets	I-Protocol
and	O
recording	O
the	O
address/identifier	O
of	O
each	O
connected	O
node	B-Protocol
and	O
which	O
port	O
it	O
is	O
connected	O
to	O
in	O
a	O
lookup	B-Data_Structure
table	I-Data_Structure
held	O
in	O
memory	O
.	O
</s>
<s>
This	O
lookup	B-Data_Structure
table	I-Data_Structure
then	O
allows	O
future	O
transmissions	O
to	O
be	O
forwarded	O
to	O
the	O
intended	O
destination	O
only	O
.	O
</s>
<s>
In	O
a	O
partially	O
connected	O
mesh	B-Architecture
topology	I-Architecture
,	O
there	O
are	O
at	O
least	O
two	O
nodes	B-Protocol
with	O
two	O
or	O
more	O
paths	O
between	O
them	O
to	O
provide	O
redundant	O
paths	O
in	O
case	O
the	O
link	O
providing	O
one	O
of	O
the	O
paths	O
fails	O
.	O
</s>
<s>
Decentralization	O
is	O
often	O
used	O
to	O
compensate	O
for	O
the	O
single-point-failure	O
disadvantage	O
that	O
is	O
present	O
when	O
using	O
a	O
single	O
device	O
as	O
a	O
central	O
node	B-Protocol
(	O
e.g.	O
,	O
in	O
star	B-Architecture
and	O
tree	B-Data_Structure
networks	I-Data_Structure
)	O
.	O
</s>
<s>
A	O
special	O
kind	O
of	O
mesh	B-Architecture
,	O
limiting	O
the	O
number	O
of	O
hops	O
between	O
two	O
nodes	B-Protocol
,	O
is	O
a	O
hypercube	B-Operating_System
.	O
</s>
<s>
The	O
number	O
of	O
arbitrary	O
forks	O
in	O
mesh	B-Architecture
networks	I-Architecture
makes	O
them	O
more	O
difficult	O
to	O
design	O
and	O
implement	O
,	O
but	O
their	O
decentralized	O
nature	O
makes	O
them	O
very	O
useful	O
.	O
</s>
<s>
This	O
is	O
similar	O
in	O
some	O
ways	O
to	O
a	O
grid	B-Protocol
network	I-Protocol
,	O
where	O
a	O
linear	O
or	O
ring	B-Architecture
topology	I-Architecture
is	O
used	O
to	O
connect	O
systems	O
in	O
multiple	O
directions	O
.	O
</s>
<s>
A	O
multidimensional	O
ring	B-Architecture
has	O
a	O
toroidal	O
topology	B-Architecture
,	O
for	O
instance	O
.	O
</s>
<s>
A	O
fully	O
connected	O
network	O
,	O
complete	O
topology	B-Architecture
,	O
or	O
full	O
mesh	B-Architecture
topology	I-Architecture
is	O
a	O
network	B-Architecture
topology	I-Architecture
in	O
which	O
there	O
is	O
a	O
direct	O
link	O
between	O
all	O
pairs	O
of	O
nodes	B-Protocol
.	O
</s>
<s>
In	O
a	O
fully	O
connected	O
network	O
with	O
n	O
nodes	B-Protocol
,	O
there	O
are	O
direct	O
links	O
.	O
</s>
<s>
Networks	O
designed	O
with	O
this	O
topology	B-Architecture
are	O
usually	O
very	O
expensive	O
to	O
set	O
up	O
,	O
but	O
provide	O
a	O
high	O
degree	O
of	O
reliability	O
due	O
to	O
the	O
multiple	O
paths	O
for	O
data	O
that	O
are	O
provided	O
by	O
the	O
large	O
number	O
of	O
redundant	O
links	O
between	O
nodes	B-Protocol
.	O
</s>
<s>
This	O
topology	B-Architecture
is	O
mostly	O
seen	O
in	O
military	O
applications	O
.	O
</s>
