'''Multicast Source Discovery Protocol''' is a [[protocol]] designedthat allows to allowinterconnect two different [[Sparse_multicast|PIM-SM]] [[multicast]] [[domains]] to interconnect. This enablesallows PIM-SM to have RP [[redundancy|RP redundancy]] and interdomain multicasting. It is described in more detail in experimental [[Request_for_Comments|RFC]]inter-___domain 3618multicasts.