MBGP
Multiprotocol Extensions to BGP (RFC 2283).
Tag unicast prefixes as multicast source prefixes for intra-domain
mcast routing protocols to do RPF checks.
WHY?  Allows for interdomain RPF checking where unicast and
multicast paths are non-congruent.
DO I REALLY NEED IT?
YES, if:
ISP to ISP peering
Multiple-homed networks
NO, if:
You are single-homed