<s>
A	O
path-vector	B-Protocol
routing	I-Protocol
protocol	I-Protocol
is	O
a	O
network	O
routing	B-Protocol
protocol	I-Protocol
which	O
maintains	O
the	O
path	O
information	O
that	O
gets	O
updated	O
dynamically	O
.	O
</s>
<s>
This	O
algorithm	O
is	O
sometimes	O
used	O
in	O
Bellman	B-Algorithm
–	I-Algorithm
Ford	I-Algorithm
routing	I-Algorithm
algorithms	I-Algorithm
to	O
avoid	O
"	O
Count	O
to	O
Infinity	O
"	O
problems	O
.	O
</s>
<s>
It	O
is	O
different	O
from	O
the	O
distance	B-Protocol
vector	I-Protocol
routing	I-Protocol
and	O
link	B-Protocol
state	I-Protocol
routing	I-Protocol
.	O
</s>
<s>
Border	B-Protocol
Gateway	I-Protocol
Protocol	I-Protocol
(	O
BGP	B-Protocol
)	O
is	O
an	O
example	O
of	O
a	O
path	B-Protocol
vector	I-Protocol
protocol	I-Protocol
.	O
</s>
<s>
In	O
BGP	B-Protocol
,	O
the	O
autonomous	B-Architecture
system	I-Architecture
boundary	O
routers	O
(	O
ASBR	O
)	O
send	O
path-vector	O
messages	O
to	O
advertise	O
the	O
reachability	O
of	O
networks	O
.	O
</s>
<s>
Each	O
router	O
that	O
receives	O
a	O
path	B-Protocol
vector	I-Protocol
message	O
must	O
verify	O
the	O
advertised	O
path	O
according	O
to	O
its	O
policy	O
.	O
</s>
<s>
It	O
modifies	O
the	O
routing	O
table	O
to	O
maintain	O
the	O
autonomous	B-Architecture
systems	I-Architecture
that	O
are	O
traversed	O
in	O
order	O
to	O
reach	O
the	O
destination	O
system	O
.	O
</s>
<s>
It	O
modifies	O
the	O
message	O
to	O
add	O
its	O
AS	B-Architecture
number	I-Architecture
and	O
to	O
replace	O
the	O
next	O
router	O
entry	O
with	O
its	O
identification	O
.	O
</s>
<s>
Exterior	B-Protocol
Gateway	I-Protocol
Protocol	I-Protocol
(	O
EGP	O
)	O
does	O
not	O
use	O
path	B-Protocol
vectors	I-Protocol
.	O
</s>
<s>
Of	O
note	O
,	O
BGP	B-Protocol
is	O
commonly	O
referred	O
to	O
as	O
an	O
External	O
Gateway	O
Protocol	O
(	O
EGP	O
)	O
given	O
its	O
role	O
in	O
connecting	O
Autonomous	B-Architecture
Systems	I-Architecture
(	O
AS	O
)	O
.	O
</s>
<s>
This	O
being	O
said	O
,	O
BGP	B-Protocol
can	O
be	O
used	O
within	O
an	O
AS	O
,	O
which	O
typically	O
occurs	O
within	O
very	O
large	O
organizations	O
such	O
as	O
Facebook	O
or	O
Microsoft	O
.	O
</s>
