<s>
Multiprotocol	B-Protocol
Extensions	I-Protocol
for	I-Protocol
BGP	I-Protocol
(	O
MBGP	B-Protocol
or	O
MP-BGP	B-Protocol
)	O
,	O
sometimes	O
referred	O
to	O
as	O
Multiprotocol	B-Protocol
BGP	I-Protocol
or	O
Multicast	B-Protocol
BGP	I-Protocol
and	O
defined	O
in	O
IETF	O
RFC	O
4760	O
,	O
is	O
an	O
extension	O
to	O
Border	B-Protocol
Gateway	I-Protocol
Protocol	I-Protocol
(	O
BGP	B-Protocol
)	O
that	O
allows	O
different	O
types	O
of	O
addresses	O
(	O
known	O
as	O
address	O
families	O
)	O
to	O
be	O
distributed	O
in	O
parallel	O
.	O
</s>
<s>
Whereas	O
standard	O
BGP	B-Protocol
supports	O
only	O
IPv4	B-Protocol
unicast	B-Protocol
addresses	O
,	O
Multiprotocol	B-Protocol
BGP	I-Protocol
supports	O
IPv4	B-Protocol
and	O
IPv6	B-Protocol
addresses	I-Protocol
and	O
it	O
supports	O
unicast	B-Protocol
and	O
multicast	O
variants	O
of	O
each	O
.	O
</s>
<s>
Multiprotocol	B-Protocol
BGP	I-Protocol
allows	O
information	O
about	O
the	O
topology	O
of	O
IP	O
multicast-capable	O
routers	O
to	O
be	O
exchanged	O
separately	O
from	O
the	O
topology	O
of	O
normal	O
IPv4	B-Protocol
unicast	B-Protocol
routers	O
.	O
</s>
<s>
Thus	O
,	O
it	O
allows	O
a	O
multicast	O
routing	O
topology	O
different	O
from	O
the	O
unicast	B-Protocol
routing	O
topology	O
.	O
</s>
<s>
Although	O
MBGP	B-Protocol
enables	O
the	O
exchange	O
of	O
inter-domain	O
multicast	O
routing	O
information	O
,	O
other	O
protocols	O
such	O
as	O
the	O
Protocol	B-Protocol
Independent	I-Protocol
Multicast	I-Protocol
family	O
are	O
needed	O
to	O
build	O
trees	O
and	O
forward	O
multicast	O
traffic	O
.	O
</s>
<s>
As	O
an	O
enhancement	O
of	O
BGP-4	O
,	O
MP-BGP	B-Protocol
provides	O
routing	O
information	O
for	O
various	O
protocols	O
,	O
such	O
as	O
IPv6	O
(	O
BGP4+	O
)	O
and	O
multicast	O
:	O
</s>
<s>
MP-BGP	B-Protocol
maintains	O
unicast	B-Protocol
and	O
multicast	O
routing	O
information	O
,	O
and	O
stores	O
both	O
types	O
in	O
different	O
routing	O
tables	O
to	O
ensure	O
their	O
separation	O
.	O
</s>
<s>
MP-BGP	B-Protocol
supports	O
unicast	B-Protocol
and	O
multicast	O
,	O
and	O
constructs	O
different	O
network	O
topologies	O
for	O
each	O
.	O
</s>
<s>
MP-BGP	B-Protocol
can	O
maintain	O
unicast	B-Protocol
and	O
multicast	O
routes	O
based	O
on	O
routing	O
policies	O
.	O
</s>
<s>
The	O
unicast	B-Protocol
routing	O
policies	O
and	O
configurations	O
supported	O
by	O
BGP-4	O
can	O
mostly	O
be	O
applied	O
to	O
multicast	O
.	O
</s>
<s>
Multiprotocol	B-Protocol
BGP	I-Protocol
is	O
also	O
widely	O
deployed	O
in	O
case	O
of	O
MPLS	O
L3	O
VPN	O
,	O
to	O
exchange	O
VPN	O
labels	O
learned	O
for	O
the	O
routes	O
from	O
the	O
customer	O
sites	O
over	O
the	O
MPLS	O
network	O
,	O
in	O
order	O
to	O
distinguish	O
between	O
different	O
customer	O
sites	O
when	O
the	O
traffic	O
from	O
the	O
other	O
customer	O
sites	O
comes	O
to	O
the	O
provider	B-Protocol
edge	I-Protocol
router	I-Protocol
(	O
PE	B-Protocol
router	I-Protocol
)	O
for	O
routing	O
.	O
</s>
