<s>
A	O
broadcast	B-General_Concept
storm	I-General_Concept
or	O
broadcast	B-General_Concept
radiation	I-General_Concept
is	O
the	O
accumulation	O
of	O
broadcast	B-Operating_System
and	O
multicast	O
traffic	O
on	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
Extreme	O
amounts	O
of	O
broadcast	B-Operating_System
traffic	I-Operating_System
constitute	O
a	O
"	O
broadcast	B-General_Concept
storm	I-General_Concept
"	O
.	O
</s>
<s>
A	O
packet	B-Protocol
that	O
induces	O
such	O
a	O
storm	O
is	O
occasionally	O
nicknamed	O
a	O
Chernobyl	B-General_Concept
packet	I-General_Concept
.	O
</s>
<s>
Most	O
commonly	O
the	O
cause	O
is	O
a	O
switching	B-Architecture
loop	I-Architecture
in	O
the	O
Ethernet	O
network	B-Architecture
topology	I-Architecture
(	O
i.e.	O
</s>
<s>
As	O
broadcasts	B-Operating_System
and	O
multicasts	O
are	O
forwarded	O
by	O
switches	O
out	O
of	O
every	O
port	B-Protocol
,	O
the	O
switch	O
or	O
switches	O
will	O
repeatedly	O
rebroadcast	O
broadcast	B-Operating_System
messages	O
and	O
flood	O
the	O
network	O
.	O
</s>
<s>
Since	O
the	O
layer-2	B-Protocol
header	O
does	O
not	O
support	O
a	O
time	B-Protocol
to	I-Protocol
live	I-Protocol
(	O
TTL	O
)	O
value	O
,	O
if	O
a	O
frame	B-Protocol
is	O
sent	O
into	O
a	O
looped	O
topology	B-Architecture
,	O
it	O
can	O
loop	O
forever	O
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
a	O
broadcast	B-General_Concept
storm	I-General_Concept
can	O
be	O
instigated	O
for	O
the	O
purpose	O
of	O
a	O
denial	O
of	O
service	O
(	O
DOS	O
)	O
using	O
one	O
of	O
the	O
packet	B-Protocol
amplification	O
attacks	O
,	O
such	O
as	O
the	O
smurf	O
attack	O
or	O
fraggle	O
attack	O
,	O
where	O
an	O
attacker	O
sends	O
a	O
large	O
amount	O
of	O
ICMP	B-Protocol
Echo	I-Protocol
Requests	I-Protocol
(	O
ping	B-Protocol
)	O
traffic	O
to	O
a	O
broadcast	B-Operating_System
address	O
,	O
with	O
each	O
ICMP	B-Protocol
Echo	I-Protocol
packet	B-Protocol
containing	O
the	O
spoof	O
source	O
address	O
of	O
the	O
victim	O
host	O
.	O
</s>
<s>
When	O
the	O
spoofed	O
packet	B-Protocol
arrives	O
at	O
the	O
destination	O
network	O
,	O
all	O
hosts	O
on	O
the	O
network	O
reply	O
to	O
the	O
spoofed	O
address	O
.	O
</s>
<s>
The	O
initial	O
Echo	B-Protocol
Request	I-Protocol
is	O
multiplied	O
by	O
the	O
number	O
of	O
hosts	O
on	O
the	O
network	O
.	O
</s>
<s>
This	O
generates	O
a	O
storm	O
of	O
replies	O
to	O
the	O
victim	O
host	O
tying	O
up	O
network	O
bandwidth	O
,	O
using	O
up	O
CPU	B-Device
resources	O
or	O
possibly	O
crashing	O
the	O
victim	O
.	O
</s>
<s>
In	O
wireless	B-General_Concept
networks	I-General_Concept
a	O
disassociation	O
packet	B-Protocol
spoofed	O
with	O
the	O
source	O
to	O
that	O
of	O
the	O
wireless	B-Device
access	I-Device
point	I-Device
and	O
sent	O
to	O
the	O
broadcast	B-Operating_System
address	O
can	O
generate	O
a	O
disassociation	O
broadcast	B-Operating_System
DOS	O
attack	O
.	O
</s>
<s>
Switching	B-Architecture
loops	I-Architecture
are	O
largely	O
addressed	O
through	O
link	B-Architecture
aggregation	I-Architecture
,	O
shortest	B-Protocol
path	I-Protocol
bridging	I-Protocol
or	O
spanning	B-Protocol
tree	I-Protocol
protocol	I-Protocol
.	O
</s>
<s>
In	O
Metro	B-Protocol
Ethernet	I-Protocol
rings	O
it	O
is	O
prevented	O
using	O
the	O
Ethernet	B-Protocol
Ring	I-Protocol
Protection	I-Protocol
Switching	I-Protocol
(	O
ERPS	B-Protocol
)	O
or	O
Ethernet	B-Protocol
Automatic	I-Protocol
Protection	I-Protocol
System	I-Protocol
(	O
EAPS	O
)	O
protocols	O
.	O
</s>
<s>
Filtering	O
broadcasts	B-Operating_System
by	O
Layer	B-Application
3	I-Application
equipment	O
,	O
typically	O
routers	B-Protocol
(	O
and	O
even	O
switches	O
that	O
employ	O
advanced	O
filtering	O
called	O
brouters	B-Device
)	O
.	O
</s>
<s>
Physically	O
segmenting	O
the	O
broadcast	B-Architecture
domains	I-Architecture
using	O
routers	B-Protocol
at	O
Layer	B-Application
3	I-Application
(	O
or	O
logically	O
with	O
VLANs	B-General_Concept
at	O
Layer	B-Protocol
2	I-Protocol
)	O
in	O
the	O
same	O
fashion	O
switches	O
decrease	O
the	O
size	O
of	O
collision	B-Protocol
domains	I-Protocol
at	O
Layer	B-Protocol
2	I-Protocol
.	O
</s>
<s>
Routers	B-Protocol
and	O
firewalls	B-Application
can	O
be	O
configured	O
to	O
detect	O
and	O
prevent	O
maliciously	O
inducted	O
broadcast	B-General_Concept
storms	I-General_Concept
(	O
e.g.	O
</s>
<s>
Broadcast	B-General_Concept
storm	I-General_Concept
control	O
is	O
a	O
feature	O
of	O
many	O
managed	O
switches	O
in	O
which	O
the	O
switch	O
intentionally	O
ceases	O
to	O
forward	O
all	O
broadcast	B-Operating_System
traffic	I-Operating_System
if	O
the	O
bandwidth	O
consumed	O
by	O
incoming	O
broadcast	B-Operating_System
frames	O
exceeds	O
a	O
designated	O
threshold	O
.	O
</s>
<s>
Although	O
this	O
does	O
not	O
resolve	O
the	O
root	O
broadcast	B-General_Concept
storm	I-General_Concept
problem	O
,	O
it	O
limits	O
broadcast	B-General_Concept
storm	I-General_Concept
intensity	O
and	O
thus	O
allows	O
a	O
network	O
manager	O
to	O
communicate	O
with	O
network	O
equipment	O
to	O
diagnose	O
and	O
resolve	O
the	O
root	O
problem	O
.	O
</s>
<s>
In	O
a	O
mobile	B-Protocol
ad	I-Protocol
hoc	I-Protocol
network	I-Protocol
(	O
MANET	O
)	O
,	O
route	O
request	O
(	O
RREQ	O
)	O
packets	B-Protocol
are	O
usually	O
broadcast	B-Operating_System
to	O
discover	O
new	O
routes	O
.	O
</s>
<s>
These	O
RREQ	O
packets	B-Protocol
may	O
cause	O
broadcast	B-General_Concept
storms	I-General_Concept
and	O
compete	O
over	O
the	O
channel	O
with	O
data	B-Protocol
packets	I-Protocol
.	O
</s>
<s>
One	O
approach	O
to	O
alleviate	O
the	O
broadcast	B-General_Concept
storm	I-General_Concept
problem	O
is	O
to	O
inhibit	O
some	O
hosts	O
from	O
rebroadcasting	O
to	O
reduce	O
the	O
redundancy	O
,	O
and	O
thus	O
contention	O
and	O
collision	O
.	O
</s>
