<s>
Multicast	B-Protocol
Source	I-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
(	O
MSDP	B-Protocol
)	O
is	O
a	O
Protocol	B-Protocol
Independent	I-Protocol
Multicast	I-Protocol
(	O
PIM	O
)	O
family	O
multicast	O
routing	O
protocol	O
defined	O
by	O
Experimental	O
RFC	O
3618	O
.	O
</s>
<s>
Despite	O
becoming	O
the	O
IPv4	B-Protocol
de	O
facto	O
standard	O
for	O
inter-domain	B-Architecture
multicast	O
,	O
development	O
of	O
the	O
protocol	O
stopped	O
in	O
2006	O
and	O
it	O
was	O
decided	O
by	O
the	O
authors	O
not	O
to	O
proceed	O
with	O
making	O
it	O
a	O
proposed	O
standard	O
.	O
</s>
<s>
MSDP	B-Protocol
interconnects	O
multiple	O
IPv4	B-Protocol
PIM	O
Sparse-Mode	O
(	O
PIM-SM	O
)	O
domains	O
which	O
enables	O
PIM-SM	O
to	O
have	O
Rendezvous	O
Point	O
(	O
RP	O
)	O
redundancy	O
and	O
inter-domain	B-Architecture
multicasting	O
RFC	O
4611	O
.	O
</s>
<s>
MSDP	B-Protocol
uses	O
TCP	B-Protocol
as	O
its	O
transport	O
protocol	O
.	O
</s>
<s>
All	O
of	O
the	O
RPs	O
are	O
peers	O
(	O
directly	O
or	O
through	O
other	O
MSDP	B-Protocol
peers	O
)	O
.	O
</s>
<s>
In	O
a	O
peering	O
relationship	O
,	O
one	O
MSDP	B-Protocol
peer	O
listens	O
for	O
new	O
TCP	B-Protocol
connections	O
on	O
the	O
well-known	O
port	O
639	O
.	O
</s>
<s>
MSDP	B-Protocol
is	O
deliberately	O
unspecified	O
for	O
IPv6	O
,	O
for	O
a	O
number	O
of	O
reasons	O
,	O
including	O
that	O
protocols	O
such	O
as	O
Source-Specific	B-Protocol
Multicast	I-Protocol
(	O
SSM	O
)	O
,	O
Bi-directional	O
Multicast	O
and	O
IPv6	O
Embedded	O
Rendezvous	O
Points	O
would	O
mean	O
there	O
was	O
less	O
requirement	O
for	O
MSDP	B-Protocol
.	O
</s>
