<s>
In	O
Multiprotocol	B-Protocol
Label	I-Protocol
Switching	I-Protocol
(	O
MPLS	B-Protocol
)	O
,	O
a	O
P	B-General_Concept
router	I-General_Concept
or	O
provider	B-General_Concept
router	I-General_Concept
is	O
a	O
label	B-Protocol
switch	I-Protocol
router	I-Protocol
(	O
LSR	O
)	O
that	O
functions	O
as	O
a	O
transit	O
router	O
of	O
the	O
core	O
network	O
.	O
</s>
<s>
The	O
P	B-General_Concept
router	I-General_Concept
is	O
typically	O
connected	O
to	O
one	O
or	O
more	O
PE	B-Protocol
routers	I-Protocol
.	O
</s>
<s>
Here	O
's	O
one	O
scenario	O
:	O
A	O
customer	O
who	O
has	O
facilities	O
in	O
LA	O
and	O
Atlanta	O
wants	O
to	O
connect	O
these	O
sites	O
over	O
an	O
MPLS	B-Application
VPN	I-Application
provided	O
by	O
AT&T	O
.	O
</s>
<s>
To	O
do	O
this	O
,	O
the	O
customer	O
would	O
purchase	O
a	O
link	O
from	O
the	O
on-site	O
CE	B-Protocol
router	I-Protocol
to	O
the	O
PE	B-Protocol
router	I-Protocol
in	O
T	O
's	O
central	O
office	O
in	O
LA	O
and	O
would	O
also	O
do	O
the	O
same	O
thing	O
in	O
Atlanta	O
.	O
</s>
<s>
The	O
PE	B-Protocol
routers	I-Protocol
would	O
connect	O
over	O
T	O
's	O
backbone	O
routers	O
(	O
P	B-General_Concept
routers	I-General_Concept
)	O
to	O
enable	O
the	O
two	O
CE	B-Protocol
routers	I-Protocol
in	O
LA	O
and	O
Atlanta	O
to	O
communicate	O
over	O
the	O
MPLS	B-Protocol
network	O
.	O
</s>
