<s>
Penultimate	B-General_Concept
hop	I-General_Concept
popping	I-General_Concept
(	O
PHP	O
)	O
is	O
a	O
function	O
performed	O
by	O
certain	O
routers	B-Protocol
in	O
an	O
MPLS	B-Protocol
enabled	O
network	O
.	O
</s>
<s>
It	O
refers	O
to	O
the	O
process	O
whereby	O
the	O
outermost	O
label	O
of	O
an	O
MPLS	B-Protocol
tagged	O
packet	O
is	O
removed	O
by	O
a	O
Label	B-Protocol
Switch	I-Protocol
Router	I-Protocol
(	O
LSR	O
)	O
before	O
the	O
packet	O
is	O
passed	O
to	O
an	O
adjacent	O
Label	B-Protocol
Edge	I-Protocol
Router	I-Protocol
(	O
LER	O
)	O
.	O
</s>
<s>
The	O
process	O
is	O
important	O
in	O
a	O
Layer	B-Application
3	I-Application
MPLS	I-Application
VPN	I-Application
(	O
)	O
environment	O
as	O
it	O
reduces	O
the	O
load	O
on	O
the	O
LER	O
.	O
</s>
<s>
The	O
outer	O
label	O
,	O
identifying	O
that	O
the	O
packet	O
was	O
destined	O
to	O
have	O
its	O
label	O
stripped	O
on	O
this	O
router	B-Protocol
.	O
</s>
<s>
The	O
inner	O
label	O
,	O
to	O
identify	O
which	O
Virtual	B-General_Concept
Routing	I-General_Concept
and	I-General_Concept
Forwarding	I-General_Concept
(	O
VRF	O
)	O
instance	O
to	O
use	O
for	O
the	O
subsequent	O
IP	O
routing	O
lookup	O
.	O
</s>
