<s>
Heuristic	B-Protocol
routing	I-Protocol
is	O
a	O
system	O
used	O
to	O
describe	O
how	O
deliveries	O
are	O
made	O
when	O
problems	O
in	O
a	O
network	B-Architecture
topology	I-Architecture
arise	O
.	O
</s>
<s>
Heuristic	B-Algorithm
is	O
an	O
adjective	O
used	O
in	O
relation	O
to	O
methods	O
of	O
learning	O
,	O
discovery	O
,	O
or	O
problem	O
solving	O
.	O
</s>
<s>
Routing	B-Protocol
is	O
the	O
process	O
of	O
selecting	O
paths	O
to	O
specific	O
destinations	O
.	O
</s>
<s>
Heuristic	B-Protocol
routing	I-Protocol
is	O
used	O
for	O
traffic	O
in	O
the	O
telecommunications	O
networks	O
and	O
transport	O
networks	O
of	O
the	O
world	O
.	O
</s>
<s>
Heuristic	B-Protocol
routing	I-Protocol
is	O
achieved	O
using	O
specific	O
algorithms	O
to	O
determine	O
a	O
better	O
,	O
although	O
not	O
always	O
optimal	O
,	O
path	O
to	O
a	O
destination	O
.	O
</s>
<s>
When	O
an	O
interruption	O
in	O
a	O
network	B-Architecture
topology	I-Architecture
occurs	O
,	O
the	O
software	O
running	O
on	O
the	O
networking	O
electronics	O
can	O
calculate	O
another	O
route	O
to	O
the	O
desired	O
destination	O
via	O
an	O
alternate	O
available	O
path	O
.	O
</s>
<s>
The	O
heuristic	B-Algorithm
approach	O
to	O
problem	O
solving	O
consists	O
of	O
applying	O
human	O
intelligence	O
,	O
experience	O
,	O
common	O
sense	O
and	O
certain	O
rules	O
of	O
thumb	O
(	O
or	O
heuristics	B-Algorithm
)	O
to	O
develop	O
an	O
acceptable	O
,	O
but	O
not	O
necessarily	O
an	O
optimum	O
,	O
solution	O
to	O
a	O
problem	O
.	O
</s>
<s>
Often	O
the	O
effort	O
(	O
manpower	O
,	O
computer	O
,	O
and	O
other	O
resources	O
)	O
required	O
,	O
the	O
time	O
limits	O
on	O
when	O
the	O
solution	O
is	O
needed	O
,	O
and	O
the	O
cost	O
to	O
compile	O
,	O
process	O
,	O
and	O
analyze	O
all	O
the	O
data	O
required	O
for	O
deterministic	O
or	O
other	O
complicated	O
procedures	O
preclude	O
their	O
usefulness	O
or	O
favor	O
the	O
faster	O
,	O
simpler	O
heuristic	B-Algorithm
approach	O
.	O
</s>
<s>
Thus	O
,	O
the	O
heuristic	B-Algorithm
approach	O
is	O
generally	O
used	O
when	O
deterministic	O
techniques	O
or	O
are	O
not	O
available	O
,	O
economical	O
,	O
or	O
practical	O
.	O
</s>
<s>
Heuristic	B-Protocol
routing	I-Protocol
allows	O
a	O
measure	O
of	O
route	O
optimization	O
in	O
telecommunications	O
networks	O
based	O
on	O
recent	O
empirical	O
knowledge	O
of	O
the	O
state	O
of	O
the	O
network	O
.	O
</s>
<s>
Data	O
,	O
such	O
as	O
time	O
delay	B-Protocol
,	O
may	O
be	O
extracted	O
from	O
incoming	O
messages	O
,	O
during	O
specified	O
periods	O
and	O
over	O
different	O
routes	O
,	O
and	O
used	O
to	O
determine	O
the	O
optimum	O
routing	B-Protocol
for	O
transmitting	O
data	O
back	O
to	O
the	O
sources	O
.	O
</s>
<s>
The	O
IP	B-Protocol
routing	I-Protocol
protocols	O
in	O
use	O
today	O
are	O
based	O
on	O
one	O
of	O
two	O
algorithms	O
:	O
distance	O
vector	O
or	O
link	O
state	O
.	O
</s>
<s>
Distance	O
vector	O
algorithms	O
broadcast	O
routing	B-Protocol
information	I-Protocol
to	O
all	O
neighboring	O
routers	O
.	O
</s>
<s>
Link	O
state	O
routing	B-Protocol
protocols	O
build	O
a	O
topographical	O
map	O
of	O
the	O
entire	O
network	O
based	O
on	O
updates	O
from	O
neighbor	O
routers	O
,	O
and	O
then	O
use	O
the	O
Dijkstra	B-Algorithm
algorithm	I-Algorithm
to	O
compute	O
the	O
shortest	O
path	O
to	O
each	O
destination	O
.	O
</s>
<s>
Metrics	O
used	O
are	O
based	O
on	O
the	O
number	O
of	O
hops	O
,	O
delay	B-Protocol
,	O
throughput	O
,	O
traffic	O
,	O
and	O
reliability	O
.	O
</s>
<s>
OSPF	B-Protocol
uses	O
the	O
Dijkstra	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
