<s>
A	O
gossip	B-Operating_System
protocol	I-Operating_System
or	O
epidemic	B-Operating_System
protocol	I-Operating_System
is	O
a	O
procedure	O
or	O
process	O
of	O
computer	O
peer-to-peer	O
communication	O
that	O
is	O
based	O
on	O
the	O
way	O
epidemics	B-Application
spread	O
.	O
</s>
<s>
Some	O
distributed	B-Architecture
systems	I-Architecture
use	O
peer-to-peer	O
gossip	O
to	O
ensure	O
that	O
data	O
is	O
disseminated	O
to	O
all	O
members	O
of	O
a	O
group	O
.	O
</s>
<s>
Some	O
ad-hoc	B-General_Concept
networks	I-General_Concept
have	O
no	O
central	O
registry	O
and	O
the	O
only	O
way	O
to	O
spread	O
common	O
data	O
is	O
to	O
rely	O
on	O
each	O
member	O
to	O
pass	O
it	O
along	O
to	O
their	O
neighbors	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
gossip	B-Operating_System
protocol	I-Operating_System
might	O
employ	O
some	O
of	O
these	O
ideas	O
:	O
</s>
<s>
It	O
is	O
useful	O
to	O
distinguish	O
two	O
prevailing	O
styles	O
of	O
gossip	B-Operating_System
protocol	I-Operating_System
:	O
</s>
<s>
As	O
a	O
side	O
effect	O
of	O
aggregation	O
,	O
it	O
is	O
possible	O
to	O
solve	O
other	O
kinds	O
of	O
problems	O
using	O
gossip	O
;	O
for	O
example	O
,	O
there	O
are	O
gossip	B-Operating_System
protocols	I-Operating_System
that	O
can	O
arrange	O
the	O
nodes	O
in	O
a	O
gossip	O
overlay	O
into	O
a	O
list	O
sorted	O
by	O
node-id	O
(	O
or	O
some	O
other	O
attribute	O
)	O
in	O
logarithmic	O
time	O
using	O
aggregation-style	O
exchanges	O
of	O
information	O
.	O
</s>
<s>
For	O
example	O
,	O
Internet	O
routing	B-Protocol
protocols	I-Protocol
often	O
use	O
gossip-like	O
information	O
exchanges	O
.	O
</s>
<s>
A	O
gossip	O
substrate	O
can	O
be	O
used	O
to	O
implement	O
a	O
standard	O
routed	B-Protocol
network	O
:	O
nodes	O
"	O
gossip	O
"	O
about	O
traditional	O
point-to-point	O
messages	O
,	O
effectively	O
pushing	O
traffic	O
through	O
the	O
gossip	O
layer	O
.	O
</s>
<s>
More	O
typically	O
gossip	B-Operating_System
protocols	I-Operating_System
are	O
those	O
that	O
specifically	O
run	O
in	O
a	O
regular	O
,	O
periodic	O
,	O
relatively	O
lazy	O
,	O
symmetric	O
and	O
decentralized	O
manner	O
;	O
the	O
high	O
degree	O
of	O
symmetry	O
among	O
nodes	O
is	O
particularly	O
characteristic	O
.	O
</s>
<s>
Thus	O
,	O
while	O
one	O
could	O
run	O
a	O
2-phase	B-General_Concept
commit	I-General_Concept
protocol	I-General_Concept
over	O
a	O
gossip	O
substrate	O
,	O
doing	O
so	O
would	O
be	O
at	O
odds	O
with	O
the	O
spirit	O
,	O
if	O
not	O
the	O
wording	O
,	O
of	O
the	O
definition	O
.	O
</s>
<s>
Suppose	O
that	O
we	O
want	O
to	O
find	O
the	O
object	O
that	O
most	O
closely	O
matches	O
some	O
search	O
pattern	O
,	O
within	O
a	O
network	O
of	O
unknown	O
size	O
,	O
but	O
where	O
the	O
computers	O
are	O
linked	O
to	O
one	O
another	O
and	O
where	O
each	O
machine	O
is	O
running	O
a	O
small	O
agent	O
program	O
that	O
implements	O
a	O
gossip	B-Operating_System
protocol	I-Operating_System
.	O
</s>
<s>
Gossip	B-Operating_System
protocols	I-Operating_System
have	O
also	O
been	O
used	O
for	O
achieving	O
and	O
maintaining	O
distributed	B-Operating_System
database	I-Operating_System
consistency	B-General_Concept
or	O
with	O
other	O
types	O
of	O
data	O
in	O
consistent	O
states	O
,	O
counting	O
the	O
number	O
of	O
nodes	O
in	O
a	O
network	O
of	O
unknown	O
size	O
,	O
spreading	O
news	O
robustly	O
,	O
organizing	O
nodes	O
according	O
to	O
some	O
structuring	O
policy	O
,	O
building	O
so-called	O
overlay	B-Architecture
networks	I-Architecture
,	O
computing	O
aggregates	O
,	O
sorting	O
the	O
nodes	O
in	O
a	O
network	O
,	O
electing	O
leaders	O
,	O
etc	O
.	O
</s>
<s>
Gossip	B-Operating_System
protocols	I-Operating_System
can	O
be	O
used	O
to	O
propagate	O
information	O
in	O
a	O
manner	O
rather	O
similar	O
to	O
the	O
way	O
that	O
a	O
viral	O
infection	O
spreads	O
in	O
a	O
biological	O
population	O
.	O
</s>
<s>
Indeed	O
,	O
the	O
mathematics	O
of	O
epidemics	B-Application
are	O
often	O
used	O
to	O
model	O
the	O
mathematics	O
of	O
gossip	O
communication	O
.	O
</s>
<s>
The	O
term	O
epidemic	B-Application
algorithm	O
is	O
sometimes	O
employed	O
when	O
describing	O
a	O
software	O
system	O
in	O
which	O
this	O
kind	O
of	O
gossip-based	O
information	O
propagation	O
is	O
employed	O
.	O
</s>
